a radiologic review of the new tnm classification for lung

562 AJR:194, March 2010

recurrent disease, or data collected outside of the study period [2]. Less common lung neo-plasms, such as carcinoid tumors and sarco-mas, were also excluded. Of the remaining 81,105 eligible cases, 67,725 (83.5%) were NSCLC and 13,290 (16.4%) were SCLC [3].

Of the 81,105 patients with primary lung can-cer, 36% were treated with surgery alone, 11% with radiotherapy alone, 21% with chemothera-py alone, 23% with a combination of therapies, and 9% were treated supportively [4].

Two primary methods of lung cancer stag-ing are available: clinical staging and patho-logic staging. In clinical staging, information is provided by noninvasive or minimally in-vasive techniques, such as physical examina-tion, radiologic examination, endoscopic ul-trasound, bronchoscopy, mediastinoscopy, and thoracoscopy. In pathologic staging, in-formation obtained from clinical staging is combined with findings from both the inva-sive surgical procedure and the pathologic evaluation of the excised tissue [5]. Clinical staging is important and can help to deter-mine the next appropriate step in therapy, such as the decision to proceed with patho-logic staging. However, direct comparison between the two systems is difficult because selection bias often leads to improved out-comes in those who obtain pathologic stag-ing versus those who are only staged clini-cally [4]. It is important to remember that pathologic staging remains the reference standard because the overall level of agree-ment between the two systems only ranges from 35% to 55% [5]. Of the 67,725 cases

A Radiologic Review of the New TNM Classification for Lung Cancer

Seth Kligerman1 Gerald Abbott2

Kligerman S, Abbott G

1Department of Diagnostic Radiology, University of Maryland Medical Center, 22 S Greene St., Rm. N2W78, Baltimore, MD 21201. Address correspondence to S. Kligerman ([email protected]).

2Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.

Cardiopulmonar y Imaging • Review

CMEThis article is available for CME credit.See www.arrs.org for more information.

AJR 2010; 194:562–573

0361–803X/10/1943–562

© American Roentgen Ray Society

In the United States, lung cancer remains the most common cause of cancer-related death in both men and women. In 2008, it was

estimated that lung cancer was the cause of 57% of cancer-related deaths, accounting for more deaths than breast, prostate, colon, rec-tal, and pancreatic cancers combined [1]. In 2009, the seventh edition of the TNM stag-ing system for lung cancer was published by the International Union Against Cancer and the American Joint Committee on Cancer, based on proposals from the International Staging Project of the International Associa-tion for the Study of Lung Cancer (IASLC). In addition to non–small cell lung cancer (NSCLC), the new classification system will be used to stage both small cell lung cancer (SCLC) and bronchopulmonary carcinoid tumors. Many important revisions have been made to the TNM classification of lung can-cer, and it is important for the radiologist to learn of these changes to provide more accu-rate clinical staging.

IASLC Population and MethodologyBetween 1990 and 2000, the data from

100,869 cases of newly diagnosed primary lung cancer were submitted to the Cancer Research and Biostatistics (CRAB) office. The data originated from 46 different data-bases collected across 19 countries in North America, Asia, Europe, and Australia. Of these 100,869 patients, 19,854 were excluded because of unknown histology, incomplete survival data, incomplete stage information,

Keywords: International Association for the Study of Lung Cancer (IASLC), lung cancer, staging, TNM

DOI:10.2214/AJR.09.3354

Received July 21, 2009; accepted after revision September 1, 2009.

Presented at the 2009 annual meeting of the American Roentgen Ray Society, Boston, MA. Winner of the Silver Medal.

FOCU

S O

N:

OBJECTIVE. In 2009, a new TNM staging system was published by the International Union Against Cancer and the American Joint Committee on Cancer. The new edition will encompass non–small cell lung cancer, small cell lung cancer, and bronchopulmonary car-cinoids. This article will review many important changes that have been made in the revised staging system.

CONCLUSION. It is important that radiologists learn the new system and understand the reasons for the changes to provide more accurate clinical staging.

Kligerman and AbbottNew TNM Classification for Lung Cancer

Cardiopulmonary ImagingReview

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New TNM Classification for Lung Cancer

of NSCLC in the IASLC study, clinical stag-ing was available in 53,640 cases, whereas pathologic staging was available in 33,933 cases [4, 6]. Overlap of data occurred when patients had both clinical and pathologic staging data available.

Using this large data set, survival statistics were calculated on the basis of the prognostic impact of various factors, including the T, N, and M designations as well as the final stage. Adjustments were made for cell type, sex, age, and the region where the data were collected.

All data were internally validated by origin and type of database. Additionally, external valida-tion was obtained by testing the results against data collected from 1990 to 2002 in the Na-tional Cancer Institute’s Surveillance, Epide-miology, and End Results (SEER) database.

TABLE 1: Seventh Edition of the TNM Classification of Lung Cancer Compared With the Sixth Edition

Tumor DesignationPrior System (Sixth Edition)

New System (Seventh Edition)

Five-Year Survival Rate (%)

Size

≤ 2 cm T1 T1aa 77d

> 2 but ≤ 3 cm T1 T1ba 71d

> 3 but ≤ 5 cm T2 T2aa 58d

> 5 but ≤ 7 cm T2 T2ba 49d

> 7 cm T2 T3a 35d

Pleural or pericardial invasion

Visceral pleura T2 T2ab or T2bc NAe

Parietal pleura T3 T3 NAe

Mediastinal pleura T3 T3 NAe

Parietal pericardium T3 T3 NAe

Central airway invasion

Tumor extending into mainstem bronchus > 2 cm from carina T2 T2ab or T2bc NAe

Tumor extending into mainstem bronchus ≤ 2 cm from carina T3 T3 NAe

Tumor extending to carina T4 T4 NAe

Lung atelectasis

Tumor causing atelectasis of less than entire lung T2 T2ab or T2bc NAe

Tumor causing atelectasis of entire lung T3 T3 NAe

Soft tissue invasion

Chest wall and superior sulcus T3 T3 NAe

Diaphragm T3 T3 NAe

Mediastinum T4 T4 NAe

Heart or great vessels T4 T4 NAe

Trachea T4 T4 NAe

Esophagus T4 T4 NAe

Osseous invasion

Rib T3 T3 NAe

Vertebral body T4 T4 NAe

Nerve invasion

Phrenic nerve T3 T3 NAe

Recurrent laryngeal nerve T4 T4 NAe

Note—Cells in bold indicate a change in the designation from the sixth edition. NA indicates not applicable.aT designation is listed for tumors completely surrounded by lung. Designation can increase depending on presence and extent of invasion.bT2a designation if tumor measures ≤ 5 cm in long-axis diameter.cT2b designation if tumor measures > 5 cm but ≤ 7 cm in long-axis diameter.dSurvival based on patients staged pathologically with complete resection of tumor (R0) and no nodal or extranodal metastatic disease (N0M0).eIndividual survival statistics not calculated due to limited information. As a group, 5-year survival rate in patients pathologically staged with a T3 and T4 designation (excluding those with tumors > 7 cm or satellite nodules), any R, any N, and M0 was 31% and 22%, respectively.fSurvival based on patients staged pathologically with complete or incomplete resection of tumor (any R), any nodal disease (any N), and M0.gSurvival based on patients staged pathologically with any tumor designation (any T) and M0.hSurvival based on patients staged clinically with any T and any N.

(Table 1 continues on next page)

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Kligerman and Abbott

T DesignationThe tumor (T) designation is determined

by the size of the primary tumor as mea-sured in the long-axis diameter, extent of in-vasion of the primary tumor, and presence or absence of satellite nodules (Table 1). Of 67,725 cases of NSCLC initially included in the IASLC database, 18,198 cases met the in-clusion criteria for T designation analysis by having accurate clinical or pathologic staging and no metastatic disease. Using these cases, survival statistics were calculated based on the tumor size in patients who had undergone pathologic staging and surgical resection of the primary tumor. After surgical resection, patients were classified as R0 if there was no residual disease, R1 if microscopic residual disease was present, or R2 if gross residual disease was present. In patients with nodules measuring 2 cm or less that were complete-ly surrounded by lung or visceral pleura, in the absence of nodal or extranodal metastat-ic disease (N0M0) and with complete resec-tion of tumor (R0), the 5-year survival was 77%. By comparison, patients with nodules measuring greater than 2 cm but less than or equal to 3 cm using the same criteria had a 5-year survival of 71% [7]. On the basis of these statistically significant findings, the T1 designation has been divided into T1a and

T1b (Fig. 1) using the cut points of 2 and 3 cm, respectively.

Similar calculations were performed for completely resected lung masses greater than 3 cm in patients with pathologically staged N0M0 disease, and survival differences were

optimized using cut points of 3, 5, and 7 cm. Tumors greater than 3 cm but less than or equal to 5 cm had a 5-year survival of 58%. Tumors greater than 5 cm but less than or equal to 7 cm had a 5-year survival of 49% [7]. On the basis of these findings, the T2

TABLE 1: Seventh Edition of the TNM Classification of Lung Cancer Compared With the Sixth Edition (continued)

Tumor DesignationPrior System (Sixth Edition)

New System (Seventh Edition)

Five-Year Survival Rate (%)

Satellite nodules

Same lobe T4 T3 28f

Same lung, different lobe M1 T4 22f

Lymph node designation

No lymphadenopathy N0 N0 56g

Ipsilateral, peripheral, or hilar–interlobar zone involvement N1 N1 38g

Ipsilateral upper, aorticopulmonary, lower, or subcarinal zone involvement N2 N2 22g

Supraclavicular or contralateral upper, aorticopulmonary, lower, hilar–interlobar, or peripheral zone involvement

N3 N3 6g

Metastatic disease designation

Contralateral lung metastases M1 M1a 3h

Pleural or pericardial dissemination T4 M1a 2h

Distant metastases M1 M1b 1h

Note—Cells in bold indicate a change in the designation from the sixth edition. NA indicates not applicable.aT designation is listed for tumors completely surrounded by lung. Designation can increase depending on presence and extent of invasion.bT2a designation if tumor measures ≤ 5 cm in long-axis diameter.cT2b designation if tumor measures > 5 cm but ≤ 7 cm in long-axis diameter.dSurvival based on patients staged pathologically with complete resection of tumor (R0) and no nodal or extranodal metastatic disease (N0M0).eIndividual survival statistics not calculated due to limited information. As a group, 5-year survival rate in patients pathologically staged with a T3 and T4 designation (excluding those with tumors > 7 cm or satellite nodules), any R, any N, and M0 was 31% and 22%, respectively.fSurvival based on patients staged pathologically with complete or incomplete resection of tumor (any R), any nodal disease (any N), and M0.gSurvival based on patients staged pathologically with any tumor designation (any T) and M0.hSurvival based on patients staged clinically with any T and any N.

AFig. 1—Changes to T1 designation for non–small cell lung carcinoma.A, Axial CT image in 53-year-old man shows 1.6 × 1.5 cm adenocarcinoma in right upper lobe. Any tumor measuring ≤ 2 cm in greatest diameter completely surrounded by lung or visceral pleura is now classified as T1a.B, Axial CT image in 67-year-old woman with 2.2 × 1.5 cm adenocarcinoma in right upper lobe. Any tumor measuring > 2 cm to 3 cm and completely surrounded by lung or visceral pleura is now classified as T1b.

B

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designation has been divided based on size: tumors greater than 3 cm but less than or equal to 5 cm are designated as T2a and tu-mors greater than 5 cm but less than or equal to 7 cm are designated as T2b (Fig. 2). For tumors greater than 7 cm, 5-year survival was 35%, which was similar to the 41% 5-year survival in pathologically staged T3N0M0 tumors [7]. This led to the reclassification of tumors greater than 7 cm as T3 (Fig. 3).

In the previous edition of the TNM stag-ing system, tumors were designated as T2 based not only on size but also on the extent of invasion. Tumors that invaded the visceral pleura and extended into the mainstem bron-chus but were greater than 2 cm from the carina or caused atelectasis or postobstruc-tive pneumonia without complete collapse of an entire lung were also classified as T2. However, alterations were necessary given the subdivision of the T2 designation on the basis of size in the revised staging system. Now any tumor less than or equal to 5 cm that meets any of the previously mentioned invasion criteria will be designated as T2a. Similarly, tumors greater than 5 cm but less than or equal to 7 cm with the same degree of invasion will be designated as T2b.

Accurate pathologic distinction between degrees of visceral pleural invasion has been shown to be an important prognostic indica-tor of survival [8]. However, because the vis-ceral pleura may have anywhere from four to six histologic layers, the exact definition of visceral pleural invasion has been debat-ed. Therefore, the IASLC has defined vis-ceral pleural invasion as invasion extending through the elastic layer of the visceral pleu-ra to the surface of the visceral pleura and has recommended the use of elastin stains for determination of this feature [8].

Important changes have also been made to the T3 designation in the revised TNM clas-sification. As stated previously, tumors great-er than 7 cm in size are now designated as T3. Additionally, patients with satellite nod-ules in the same lobe, previously designated as T4, have been reclassified as T3 (Fig. 3). In patients with any pattern of nodal disease (any N), M0, and with or without complete resection (any R), 5-year survival was 28%, which is similar to the 31% for other T3 le-sions using the same staging criteria [7].

Many of the T3 designations will remain unchanged in the new revisions, primarily be-cause their incidence was not high enough for accurate statistical survival analysis. Tumors that invade the diaphragm, phrenic nerve, me-

diastinal pleura, or parietal pericardium (Fig. 4) are still classified as T3. Similarly, tumors that invade the parietal pleura or chest wall, including superior sulcus tumors or tumors that destroy ribs, are still classified as T3. Tu-mors in the mainstem bronchi less than 2 cm

from the carina but not involving the carina or tumors of any size that cause atelectasis or postobstructive pneumonia of an entire lung (Fig. 4) will still be designated as T3.

Tumors with a malignant nodule in a differ-ent lobe but in the same lung were classified

AFig. 2—Changes to T2 designation for non–small cell lung carcinoma.A, Axial CT scan in 72-year-old man shows 3.2 × 2.2 cm adenocarcinoma in right upper lobe. Any tumor > 3 cm but ≤ 5 cm completely surrounded by lung is now classified as T2a.B, Axial chest CT in 77-year-old man shows 5.5 × 5.2 cm squamous cell carcinoma in left upper lobe. Any tumor > 5 cm and ≤ 7 cm completely surrounded by lung or visceral pleura is now designated as T2b.

B

AFig. 3—Revisions to T3 designation for non–small cell lung carcinoma.A, Axial chest CT in 78-year-old woman shows 8.3 × 6.4 cm large cell carcinoma in right upper lobe. Any tumor measuring ≥ 7 cm is now designated at least as T3.B, Curved coronal multiplanar reformation CT image in 71-year-old man shows small 1.6-cm adenocarcinoma in left upper lobe nodule with adjacent 8.0-mm satellite nodule. Presence of satellite nodule in same lobe has been redesignated as T3 in new staging system.

B

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as M1 disease in the prior edition. However, the 5-year survival was 22% in patients patho-logically staged with this pattern of disease, any pattern of nodal disease (any N), and with or without complete resection (any R). This is identical to the 22% 5-year survival in patients with other T4 tumors staged using similar pathologic criteria, leading to its re-classification as T4 [7] (Fig. 5 and Table 1). Other masses that meet the T4 designation include tumors that invade the mediastinum, carina, trachea, esophagus, great vessels, and heart (Fig. 6). Invasion of the recurrent laryngeal nerve or vertebral body also will lead to designation of a tumor as T4 (Fig. 7).

Because the incidence of invasion of these vital structures was relatively low in the study population, survival statistics could not be calculated, and therefore their designation remains unchanged.

Numerous changes have been made to the T designation for NSCLC between the

new and prior TNM classifications (Table 1). These changes were validated internally by the CRAB database and externally by the SEER database. Additionally, many recent publications have also validated these rec-ommendations, adding further support to the new revisions [9–12].

A

Fig. 4—T3 designation for non–small cell lung carcinoma.A, Axial CT image in 47-year-old woman shows 6.7 × 4.2 cm mass in lingula with invasion into chest wall (white arrow) and parietal pericardium (black arrow). Mass also invades into location of phrenic nerve (star), which was confirmed at pathology.B, Coronal chest CT image in 44-year-old woman shows 6.8 × 5.6 cm large cell carcinoma in right lower lobe with invasion of diaphragm but no hepatic invasion on pathologic evaluation.C, Coronal contrast-enhanced CT image in 66-year-old man shows complete atelectasis of left lung by 6.4 × 3.5 cm left hilar mass (white arrow), which is difficult to differentiate from surrounding atelectatic lung. Mass extends into mainstem bronchus (black arrow) 1.9 cm from carina but does not involve carina.

CB

AFig. 5—Revision to T4 designation for non–small cell lung carcinoma. Coronal CT image in 64-year-old man shows 5.2 × 4.5 cm large cell carcinoma in right upper lobe with 1.4-cm metastatic nodule in right middle lobe (arrow). Satellite nodule in same lung but in different lobe from primary tumor was previously classified as metastatic disease but is now designated as T4.

B

C

Fig. 6—T4 designation for non–small cell lung carcinoma.A, Axial CT image in 51-year-old man shows 8.8 × 6.5 cm adenocarcinoma invading into mediastinum with invasion of right pulmonary artery, bronchus intermedius, and carina.B, Axial CT image in 63-year-old woman shows 7.2 × 6.1 cm squamous cell carcinoma extending into mediastinum, with invasion of trachea (white arrow) and esophagus (black arrow).C, Axial multiplanar reformation image 8 mm thick in 84-year-old woman shows large squamous cell carcinoma engulfing heavily calcified branches of left coronary artery (circle). Mass also invades and obstructs left inferior and superior pulmonary veins (arrow). Any mass that invades mediastinum, esophagus, trachea, carina, or great vessels is still designated as T4.

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N DesignationThe nodal (N) designation is determined

by the presence or absence of metastatic in-volvement of lymph nodes throughout the tho-rax (Table 1). To determine if changes needed to be made to the N designation for NSCLC, 68,463 patients with M0 disease were evalu-ated. However, slight differences between the American Thoracic Society (Mountain-Dressler) and Japanese nodal maps made sta-tistical analysis difficult. To reconcile these differences, a new nodal chart was created that placed lymph nodes into seven specific zones: supraclavicular, upper, aorticopulmo-nary, subcarinal, lower, hilar–interlobar, and peripheral [13] (Fig. 8). Although the nomen-clature has changed, the general concept re-mains the same. Patients without nodal meta-static disease are designated as N0. Patients with N1 disease are defined as having meta-static involvement of lymph nodes in the ip-silateral peripheral or hilar zones (Fig. 9). The N2 designation signifies metastatic ex-tension to lymph nodes in the ipsilateral me-diastinal (upper, aorticopulmonary, lower) or subcarinal lymph node zones (Fig. 10). The N3 nodal designation includes metastatic in-volvement of any nodes in the supraclavicu-lar lymph node zone or nodes in contralater-al mediastinal, hilar–interlobar, or peripheral zones (Fig. 11). When survival statistics were evaluated based on these nodal zones, sur-vival continually decreased in both clinical-ly and pathologically staged patients as the nodal designation increased. For instance, in those clinically staged with any T designation (any T) and without extranodal metastatic dis-ease (M0), the 5-year survival was 42%, 29%, 16%, and 7% for the N0, N1, N2, and N3 des-ignations, respectively [3].

Survival differences were also calculated on the basis of the number of lymph node zones involved in any single nodal designation. For instance, in pathologically staged patients with any T and M0, those with nodal metastases to a single N1 zone had a median survival of 52 months whereas those with metastatic spread to nodes in multiple N1 zones had a median survival of only 31 months [3]. Similar de-creases in survival were also seen in patients with multiple N2 nodal zone involvement (me-dian survival 19 months) compared with those with disease in a single N2 nodal zone (medi-an survival 35 months) [3]. Interestingly, these results showed improved survival in patients with a single N2 zone involved compared with those with multiple N1 zones involved. These findings, recently validated by an external study [14], raised the possibility of subdividing the N1 and N2 classifications into N1a (single-zone N1), N1b (multiple-zone N1), N2a (sin-gle-zone N2), and N2b (multiple-zone N2). However, when these new categories were an-alyzed in conjunction with each T stage cat-egory, an insufficient number of patients were present in each group for valid statistical analy-sis. Although no changes will be made to the N designation in the seventh edition of the TNM classification, the above findings suggest that overall disease burden, in addition to the an-atomic location of pathologically involved lymph nodes, contributes to survival.

M DesignationThe M designation refers to the presence or

absence of metastatic disease within or out-side of the thorax (Table 1). For evaluation of the M designation, survival statistical analy-ses were performed on 5,592 clinically staged T4M0 and M1 patients. Clinically staged pa-

tients with pleural dissemination of disease, any degree of nodal metastases (any N), and no extranodal metastatic disease (M0) had 1-year and 5-year survival of 36% and 2%, respectively, similar to the 45% 1-year and 3% 5-year survival in those with contralat-eral lung nodules. This is significantly worse survival than the 53% 1-year and 15% 5-year survival in clinically staged patients with oth-er T4, any N, and M0 lesions [15]. Based on these findings, dissemination of disease to the pleura or pericardium as well as metastat-ic nodules to the opposite lung will now be designated as M1a (Fig. 12). Metastatic dis-ease outside of the thorax, with a significantly worse 1-year and 5-year survival of 22% and 1%, respectively, has been reclassified as M1b [15] (Fig. 13). Although there was a small but significant survival difference between those with single and multiple sites of extrathorac-ic metastatic disease, not enough cases were available for analysis to support further subdi-vision of the M1b classification [15].

As with the T and N descriptors, exter-nal validation has confirmed the importance of the revisions to the M descriptor [11, 12]. When 12,901 patients with T4 or M1 disease were evaluated from the California Cancer Registry, the analyses confirmed that the revised M descriptors are better correlated with survival when compared with the prior edition of the TNM staging system [12]. The only discrepancy was the decreased survival in patients with dissemination of disease to the pericardium, a group with survival simi-lar to those with distant metastatic disease.

Small–Cell Lung CancerUnlike NSCLC, SCLC is seen almost ex-

clusively in smokers and is known for its rapid

A

Fig. 7—T4 designation for non–small cell lung carcinoma.A, Coronal CT image in 48-year-old woman with increasing hoarseness and left arm weakness shows large mass invading mediastinum with encasement of aorta, left subclavian artery, and left recurrent laryngeal nerve (black arrow). Mass also extends superiorly into soft tissue of neck with edema of subcutaneous tissues on left due to paralysis from brachial plexus invasion (white arrow).B, Axial CT image in 55-year-old man with adeno-carcinoma at right apex invading vertebral body and compressing spinal cord. Any tumor that invades recurrent laryngeal nerve or vertebral body is designated as T4, which is unchanged from prior system.

B

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doubling time, high growth fraction, early development of metastatic disease, and ini-tial sensitivity to chemotherapy and radiation [16–18]. Once thought to represent nearly a quarter of all cases of newly diagnosed lung cancer, the incidence of SCLC has steadily declined [19]. Despite its initial response to treatment, the long-term survival of patients with SCLC continues to be much worse than that of patients with NSCLC [18].

Of the 81,015 patients with primary lung cancers analyzed in the CRAB database, SCLC comprised 13,290 (16.4%) cases. Unlike NSCLC, the staging of SCLC had previously been subdivided into two main categories, limited disease and extensive disease. Limited disease was classified as disease limited to a single hemithorax, al-though local extension of the primary tu-mor and supraclavicular lymphadenopathy could be present if they could be included in the same radiation port as the primary

Nodal Zones Nodal Stations

Supraclavicular

Supraclavicular

Low cervical

Sternal notch

Upper

Upper paratracheal (left)

Upper paratracheal (right)

Prevascular

Retrotracheal

Lower paratracheal (right)

Lower paratracheal (left)

AorticopulmonarySubaortic (aorticopulmonary window)

Paraaortic (ascending aorta or phrenic)

LowerParaesophogeal (below carina)

Pulmonary ligament

Subcarinal Subcarinal

Hilar–InterlobarHilar

Interlobar

Peripheral

Lobar

Segmental

Subsegmental

B C

ED

A

Fig. 8—International Association for the Study of Lung Cancer nodal zones in revised staging system for lung cancer.A, Comparison of seven new lymph node zones (colored rows) compared with lymph node stations in Mountain-Dressler classification used in prior system.B–E, Single coronal and three axial CT images through mediastinum show imaging-based map of location of seven new lymph node zones (colored circles) in revised classification.

AFig. 9—N1 designation for non–small cell lung carcinoma.A, Curved coronal multiplanar reformation image from CT scan in 55-year-old woman with 1.7-cm right upper lobe adenocarcinoma (T1a) and enlarged lymph node in right hilar zone (arrow).B, Corresponding PET image shows 18F-FDG uptake in both nodule and lymph node. Metastatic disease to lymph nodes in ipsilateral hilum is designated as N1, which is unchanged.

B

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tumor [20, 21]. All other disease was staged as extensive disease.

Of the 13,290 cases of SCLC, 3,430 cas-es of clinically staged SCLC without distant metastatic disease and with full TNM data were available for statistical analysis. Except for the lack of statistical significance be-tween those with N0 and N1 disease, analy-sis showed a significant decrease in survival as both the T and N designations increased [21]. Similarly, except for a very small sub-group of eight stage IIA patients that was a statistical outlier, survival decreased as the stage increased [21]. Given these findings, the IASLC has recommended that the new

TNM staging system be applied to SCLC (Fig. 14). This recommendation is support-ed by external validation that has also shown survival being more accurately predicted us-ing the revised TNM staging system [22].

Bronchopulmonary Carcinoid Tumors

Bronchopulmonary carcinoid tumors are malignant neuroendocrine tumors that are divided into typical and atypical subtypes based on pathologic criteria. Carcinoid tu-mors exist within a spectrum of neuroen-docrine tumors of the lung that range from low-grade typical carcinoid tumors to inter-

mediate-grade atypical carcinoid tumors and high-grade small cell carcinomas and large cell carcinomas [23]. Using combined data from both the IASLC and SEER databases, survival analysis was performed on 1,829 pathologically staged patients with bron-chopulmonary carcinoid tumors using the re-vised TNM staging criteria. As with NSCLC and SCLC, as the T, N, and M designations of bronchopulmonary carcinoid tumors inde-pendently increased, there was a statistically significant decrease in 5-year survival. Simi-larly, as the stage increased, 5-year survival decreased [8]. On the basis of these findings, it has been recommended that bronchopul-monary carcinoid tumors be staged using the newly revised TNM classification (Fig. 15).

Prognostic FactorsOf the prognostic factors evaluated, patho-

logic stage, sex, cell type, and age were all in-dependently significant [24] (Table 2). These factors were also significant when clinical-ly staged cases were evaluated in a separate analysis [2]. Earlier stage of disease at the time of diagnosis, female sex, and younger age were all favorable prognostic factors [24]. In terms of cell type, patients with bronchi-oloalveolar carcinoma, either pure or mixed, have the best survival across all calculations [24]. This survival benefit is well described in the literature [25–30]. Survival in pa-tients with adenocarcinomas and squamous cell carcinomas was similar when calculated across age and sex. However, when surviv-al was calculated after making adjustments for pathologic stage, cell type, sex, and age, there was a significant survival advantage in those diagnosed with squamous cell carci-nomas compared with adenocarcinomas and large cell carcinomas [24]. A similar surviv-al advantage was also noted in patients with squamous cell carcinomas who were clini-cally staged with IIIA disease [2]. Although this would suggest some survival advantage in those with squamous cell carcinoma com-pared with these two cell types, this benefit is debated in the literature [31–35].

Smoking history was only available in 2,467 of the 9,173 pathologically staged pa-tients. Current smokers had an increased in-cidence of squamous cell carcinoma as well as an overall worse prognosis when com-pared with never smokers and prior smok-ers [24]. These findings have been validat-ed in multiple external studies [26, 36–38]. Prognosis between former smokers and nev-er smokers was less well-defined and in most

Fig. 10—N2 designation for non–small cell lung carcinoma. Curved axial multiplanar reformation CT image in 46-year-old woman shows 3.8 × 1.8 cm adenocarcinoma (T2a) in left upper lobe and metastatic involvement to both ipsilateral hilar (white arrow) and aorticopulmonary (black arrow) lymph node zones. Metastatic disease to ipsilateral mediastinal or subcarinal lymph nodes is still designated as N2.

Fig. 11—N3 designation for non–small cell lung carcinoma. Curved coronal multiplanar reformation image from CT scan in 62-year-old woman with 3.2 × 2.8 cm adenocarcinoma (T2a) in left upper lobe shows pathologic enlargement of lymph nodes in subcarinal zone (arrowhead), ipsilateral upper zone (white arrow), and supraclavicular lymph nodes (black arrow). Metastatic involvement of any lymph node in supraclavicular zone is designated as N3, which is unchanged from prior staging system.

AFig. 12—Changes to M1 designation for non–small cell lung carcinoma.A, Coronal CT image in 51-year-old man with 3.4 × 3.2 cm adenocarcinoma (T2a) in right lower lobe and single 5-mm nodule in left lower lobe (arrow), which was pathologically similar to primary tumor and was thought to represent contralateral metastatic nodule.B, Axial CT image in 37-year-old woman with large left lung mass invading mediastinum (T4). Complex pleural and pericardial effusions were malignant at cytology. Nodules in contralateral lung and malignant pleural or pericardial disease are classified as M1a in new staging system.

B

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instances, there was no survival difference between these two subsets [24].

Performance status was available in 3,027 of the 9,173 pathologically staged patients with NSCLC. Decreased performance status was associated with an increased mortality and was shown to be an independently sig-nificant factor in determining survival [24]. A similar benefit was shown in clinically staged patients [2].

Of the 13,290 cases of SCLC, prognos-tic factors were evaluated in 6,609 clinical-ly staged patients. Using the prior system for the staging of SCLC, 2,870 patients had lim-

ited disease and 3,739 had extensive disease. As seen with NSCLC, increasing age, male sex, and decreased performance status are all associated with decreased survival [2]. Extensive disease was also associated with a worse survival than in those patients with limited disease [2].

Additional factors such as biologic markers, genetic markers, and functional imaging with PET have shown significant prognostic impli-cations in the literature [2, 39, 40]. However, because the data in the CRAB database were collected from 1990 to 2000, this information was not available for statistical analysis.

Changes to the Staging SystemIn addition to revising the T, N, and M

designators, significant changes to the fi-nal staging system were made to best cor-relate decreasing survival with increasing stage (Table 3). At the same time, chang-es were made to prevent overlap in the sur-vival curves between the different stages. In the absence of metastatic disease, all T4 tu-mors with N0 or N1 nodes have been down-staged from IIIB to IIIA. T2b masses with N0M0 disease will be upstaged from IB to IIA and T2a masses with N1M0 disease will be downstaged from IIB to IIA [3].

Treatment ImplicationsBy making adjustments to the T designa-

tion, M designation, and final stage based on both short- and long-term survival charac-teristics, the revised staging system for lung cancer is more accurately correlated with sur-vival when compared with the prior staging system. Importantly, survival statistics from external studies have also confirmed the va-lidity of these changes. Not only are these changes better correlated with survival, but they also more closely reflect trends in both definitive and palliative treatment. For in-stance, in the prior TNM revision, patients with tumors designated as T4 on the basis of invasion were at least staged as IIIB, even those with N0M0 disease. Although these pa-tients were classically considered nonsurgi-cal, successful resection with improved sur-vival has been shown to be possible in select patients with direct invasion of the mediasti-num, carina, pulmonary artery, vertebral body, superior vena cava, aorta, and left atri-um [41–47]. These findings support the shift of locally invasive T4 tumors from stage IIIB to IIIA in the absence of N2 or N3 and M1a or M1b disease. Conversely, although no distinc-tion was made between T4 tumors due to in-vasion and T4 tumors due to malignant pleu-ral or pericardial disease in the prior revision, those tumors with malignant pleural or peri-cardial dissemination were clinically subcat-egorized as “wet IIIB.” Those patients were deemed inappropriate candidates for defini-tive local therapy and thus were clinically re-garded as having stage IV disease and treated only with systemic therapy [42, 45, 48]. Pa-tients with satellite nodules in the same lobe and in the same lung but a different lobe, even in the absence of nodal metastases, would have been staged as IIIB and IV, respective-ly. According to the prior system, this stag-ing would have precluded these patients from

A B

Fig. 13—Changes to M1 designation for non–small cell lung carcinoma.A, Fused PET/CT image in 49-year-old man shows 2.8-cm right lower lobe nodule (T1b) with intense 18F-FDG uptake.B, Fused coronal image from PET/CT shows increased FDG uptake in right adrenal gland (arrow) and bone. Metastatic disease outside of thorax is now classified as M1b.

Fig. 14—Classification of small cell lung cancer (SCLC) using revised TNM system. Axial CT image in 59-year-old woman shows 6.2-cm SCLC extending into mediastinum and invading pulmonary artery without evidence of disease elsewhere (T4N0M0). SCLC should be staged using new TNM classification for lung cancer.

Fig. 15—Classification of bronchopulmonary carcinoid tumors using revised TNM system. Axial 10-mm-thick maximum-intensity-projection image in 38-year-old woman with atypical carcinoid tumor shows multiple nodules and masses confined to right lower lobe without disease elsewhere (T3N0M0).

AJR:194, March 2010 571


attempted surgical resection. However, many patients with this pattern of disease did un-dergo surgical resection and their outcomes were much improved compared with patients with distant metastatic disease [45, 49–51]. This surgical evidence further supports the shift in staging in the revised seventh edition of the TNM classification of lung cancer. Al-

though staging can help direct therapy, it is important to remember that prospective clini-cal trials should be used to define optimal pa-tient treatment and not staging systems based on retrospective survival data.

For SCLC, radiotherapy and chemothera-py remain the mainstays of treatment [18]. However, a more well-defined tumor and

nodal classification system will allow more precise treatment. This precision will be of growing importance as increased radiothera-py doses or more aggressive combined ther-apies are explored for patients with more localized disease [21]. Tumor size and in-vasion also can help determine treatment in SCLC. The term “limited disease” makes no distinction between a small intraparenchy-mal SCLC without nodal disease and a large mass invading the mediastinum with meta-static disease to multiple ipsilateral lymph nodes. This is an important distinction be-cause the treatments can differ. Studies have shown that even when using the prior TNM classification, patients with stage I and pos-sibly those with stage II SCLC can benefit from surgery and neoadjuvant chemother-apy, whereas those with more extensive lo-calized disease should receive radiation and chemotherapy alone [52–54].

LimitationsDespite the extensive power of the study,

there are some limitations to the revised stag-ing system for lung cancer. The new system is based on retrospective data that were pri-marily collected from databases not specifi-cally designed to study the TNM classifica-tion of lung cancer [55]. Although tumor size was often included in the data, more precise information such as the exact site of tumor in-vasion and extent of lymph node involvement was often omitted. For this reason, much of the T3 and T4 classification remains un-changed, and no changes were made to the N classification despite significant survival differences in those with single versus mul-tiple nodal zone involvement. Additionally, important tumor characteristics, such as the presence or absence of lymphangitic spread of tumor, were not evaluated. Prognostic in-formation based on tumor biology and tu-mor genetics was not included in the study because most of these data were not widely available. Factors such as the reliability and accuracy of imaging in clinical staging and the prognostic impact of PET imaging were not addressed. Staging and treatment strate-gies were not uniform because the data were collected from 46 databases across 19 coun-tries. Finally, although the new system is the best method to date to predict patient surviv-al, all of the survival data comes from ret-rospective analysis and has not been tested prospectively. Given these limitations, a pro-spective database is currently being devel-oped to assess the validity of each component

TABLE 2: Prognostic Factors of Survival in Pathologically Staged Patients With Non–Small Cell Lung Carcinoma

Factor Median Survival (mo) Five-Year Survival Rate (%)

TNM stage

IA 95 66

IB 75 56

IIA 44 43

IIB 29 35

IIIA 19 23

Cell type

Bronchoalveolar carcinoma 83 61

Adenocarcinoma 45 44

Squamous cell carcinoma 44 43

Large cell carcinoma 34 41

Adenosquamous carcinoma 26 29

Sex

Female 66 52

Male 40 41

Age (y)

< 70 49 46

≥ 70 38 38

TABLE 3: Revisions to Stage Groupings in the Seventh Edition of the TNM Classification for Lung Tumors Compared With the Sixth Edition

Stage in Seventh Edition Stage in

Sixth Edition N0 N1 N2 N3

T1a T1 IA IIA IIIA IIIB

T1b T1 IA IIA IIIA IIIB

T2a T2 IB IIA (IIB) IIIA IIIB

T2b T2 IIA IIB IIIA IIIB

T3 (> 7 cm) T2 IIB (IB) IIIA (IIB) IIIA IIIB

T3 (invasion) T3 IIB IIIA IIIA IIIB

T3 (satellite nodule, same lobe) T4 IIIB (IIIA) IIIA (IIIB) IIIA (IIIB) IIIB

T4 (invasion) T4 IIIA (IIIB) IIIA (IIIB) IIIB IIIB

T4 (ipsilateral nodule, different lobe) M1 IIIA (IV) IIIA (IV) IIIB (IV) IIIB (IV)

M1a (pleural or pericardial dissemination) T4 IV (IIIB) IV (IIIB) IV (IIIB) IV (IIIB)

M1a (contralateral lung nodules) M1 IV IV IV IV

M1b (distant metastatic disease) M1 IV IV IV IV

Note—Cells in bold indicate a change in the stage from the sixth edition. Adjacent stage in parentheses represents staging from the sixth edition.

572 AJR:194, March 2010


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ConclusionMany important changes have occurred

with the adoption of the seventh edition of the TNM staging system for lung cancer. These changes are better correlated with sur-vival characteristics and current trends in de-finitive and palliative therapy. Because imag-ing plays such a crucial role in the evaluation of lung cancer, it is imperative that radiolo-gists become well versed in the new revision of the TNM staging system to optimize pa-tient care.

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F O R Y O U R I N F O R M A T I O N

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a radiologic review of the new tnm classification for lung

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