Proceedings of the 52nd Annual ASTRO Meeting S715

first 5-12 days after the therapeutic 131 iodine administration, as patients were released from the hospital several hours aftertreatment. was read with an 8800pc Harshaw reader. Natural background was subtracted from the reading while fading cor-rection was negligible. Swapping surface areas were performed to measure iodine contamination.

Results: The radiation exposure was: patient’s bedroom 0.58 +/- 0.66 mSv patient’s bathroom 0.24 +/- 0.22 mSv patient’s kitchen0.17 +/- 0.15 mSv patient’s living room 0.34 +/- 0.39 for the whole period after treatment. Contaminations measurements weretaken from several surface areas of patient home on day 12. No contamination of 131I above the limit of detection could be ob-served. As the limit of detection of 131I is 600 Bq, assuming a swapping factor of 0.1 will result in an upper limit of iodine con-tamination of 6000 Bq. The annual limit of iodine intake is 9x105 Bq therefore, family members returned to the house after 12 dayswould not be exposed to any significant internal iodine contamination.

Conclusions: One can assume that the doses recorded in the 3 living areas measured in this work reflect 100% compliancewith the regulatory guide published by the Ministry of Health: ‘‘the dose to family members and others will be less then5mSv’’.

Author Disclosure: A. Shlomo, None; T. Biran, None; S. Primo, None; R. Ben-Yosef, None; R. Ben-Yosef, None; M. Levita,None.

3141 Esophagogram with Barium Assessment of Multimodality Therapy Predicts Survival of Esophageal

Squamous Cell Carcinoma Patients

Q. Wang, W. Zhang, L. Wang, Z. Zhou, Z. Xiao

Chest Section, Department of Radiation Oncology, Cancer Institute(Hospital),Chinese Academy of Medical Sciences, PekingUnion Medical College, Beijing 100021, China

Purpose/Objective(s): Standard esophagogram criteria are unreliable for staging esophageal carcinoma therapy; however,change of tumor shape can identify patients who have achieved a clinical response. In the current study the authors pro-spectively compared survival between patients classified as responders and those classified as nonresponders by esophago-gram.

Materials/Methods: The shape of the tumor in esophagogram was check before and after neoadjuvant therapy in patientswho were candidates for multimodality treatment. Response was defined as no visible carcinoma in esophagogram withbarium.

Results: Of 229 patients with thoracic esophageal squamous cell carcinoma, all patients underwent preoperative RT . Themedian age was 56 years, and most patients were male (76.4%). Operations performed included Ivor-Lewis (60.3%), tran-shiatal (3.1%), three-hole (35.8%), or left thoracoabdominal (0.9%) esophagectomy. Perioperative mortality rate was 4.8%.Median overall survival (OS) of the entire group was 24 months, and the 5-year and 10-year OS rate was 30% and21%.Overall, patients with responders had a median survival and 5-year,10-year survival of 41.4 months, 49%, 33.1% com-pared with 19.2 months,26.6%, 18.9% for non-responders (p = 0.024). Patients with pathologic completely response (pCR)had an improved OS and disease-free survival (DFS) compared with those patients who were not pCR (p = 0.003 and p \0.0005, respectively). Esophagogram with barium cannot predict patient’s pathologic response who underwent preoperativeradiotherapy.

Conclusions: Patients with esophageal carcinoma who respond to neoadjuvant treatment as identified by Esophagogram with bar-ium in tumor shape have a significantly better prognosis than nonresponders.

Author Disclosure: Q. Wang, None; W. Zhang, None; L. Wang, None; Z. Zhou, None; Z. Xiao, None.

3142 Study of the Effect of Edema on D90 and Equivalent Uniform Dose in 131Cs Prostate

Brachytherapy

H. A. Jones1, T. S. Kehwar2, M. S. Huq2, R. P. Smith2

1University of Pittsburgh Medical Center, Natrona Heights, PA, 2University of Pittsburgh Medical Center,Pittsburgh, PA

Purpose/Objective(s): To study the effect of prostatic edema on D90 and equivalent dose in 131Cs prostate permanent seed im-plants.

Materials/Methods: Dose volume histograms (DVH) were generated for 31 patients, who underwent 131Cs prostate brachyther-apy, using post-implant CT images taken at or after 0, 14 and 28 days, to determine D90 and equivalent uniform dose (EUD). Theprostate volume V was divided into n number of voxels to calculate EUD using the relation EUD = -(1/a) ln[(1/V)Si vi exp(-aDi)](1) where vi is the volume of ith voxel receiving a dose of Di and i = 1,2,3,1/4 n. The a is the coefficient of lethal damage. The frac-tional EUD (FEUD) is defined as the ratio of EUD by prescribed dose (PD), i.e., FEUD = EUD/PD, which is similar to FD90.Relationship between FEUD and FD90. The best fit regression lines for FD90 and FEUD vs. ‘t’ can be described by FD90(t) =FD90(0) + [FD90(0)-a1][1-exp(-let)]; (2) FEUD(t) = FEUD(0) + [FEUD(0)-a2][1-exp(-let)]; (3) where le is the decay constantof prostatic edema, a1 and a2 are the adjustable parameters for D90 and EUD, respectively. FD90(0) and FEUD(0) are FD90and FEUD at day 0, respectively. The values of FD90 and FEUD obtained from DVH are related by the best-fit of a polynomialfunction as FEUD(t) = c0 + c1 FD90(t) + c2 [FD90(t)]2; (4) where c0, c1 and c2 are polynomial coefficients. From the definition ofEUD and FEUD and using Eq.(4), the EUD can be written as EUD(t) = PD[c0 + c1 FD90(t) + c2 {FD90(t)}2]; (5) The PD is writtenby PD(t) = (R0/l)[1-exp(-lt)], where l is the decay constant of the source. An edema half life (T1/2edema) of 9.72 days and a = 0.15Gy were used to calculate EUD for all 31 patients.

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Results: The ‘a1’ and ‘a2’ were computed using the method of least square fit of FD90 and FEUD and found to be 0.880 for FD90and 0.712 for FEUD with respective correlation coefficients (R2) of 0.9895 and 0.9788. The values of FD90(t) were calculated attimes ‘t’ and then were fitted to Eq. (4). The coefficients were found to be c0 = 0.85, c1 = 9.5 x10�3, c2 = -2.0 x 10�4. The values ofFEUD calculated using Eqs (3) and (4) are indistinguishable from each other and have statistically insignificant differences (p .

0.05). Eq. (5). This reveals that even if FEUD improves with ‘t’, the actual EUD decreases due to short half life of the 131Cs sourceand hence there is less benefit of edema decay.

Conclusions: The FD90 and EUD investigated in this study increased with increasing ‘t’ and attained optimal values in fourweeks. However, due to the short half life of 131Cs seeds the improvement is less. Therefore it is important to account for theeffect of edema at the time of implant by rearranging seed positions. The method of computing EUD using FD90 valuesdescribed in this study is simple, and these dosimetric quantities can be used to further evaluate plans and optimize treatmentplanning.

Author Disclosure: H.A. Jones, None; T.S. Kehwar, None; M.S. Huq, None; R.P. Smith, None.

3143 The Preliminary Study of Target Uncertainty during Fractional Radiotherapy in

Esophageal Cancer

X. Lu, B. Song, J. Qian, J. Huan, Y. Tian

The Second Affiliated Hospital of Soochow University, Suzhou, China

Purpose/Objective(s): To investigate the changes of target during fractional radiotherapy in esophageal cancer, and to assess theinfluence to the implementation of radiation therapy caused by these changes.

Materials/Methods: Fourteen patients with unresectable esophageal cancer were enrolled to accept full course of conformal ra-diotherapy. CT scans were acquired after every ten fractional radiotherapy. New targets were delineated on repeated CT scansagain. After that, the pretreatment radiotherapy plans were copied to the new targets to investigate the coincidence between thenew targets and the pretreatment plans.

Results: The trend of the GTV changes was decreasing during fractional radiotherapy. However, GTV of 35.7% (5/14) patientsincreased at the tenth fraction, and the increased percentage of GTV ranged from 2.0% to 37.7%. The PTV included by 95% iso-dose curve at pretreatment, tenth fraction, twentieth fraction, and thirtieth fraction were 97.81 ± 1.53%, 91.95 ± 5.25%, 94.27 ±4.23%, and 94.03 ± 6.45%, respectively. Moreover, there were 6, 5, and 4 cases whose PTV included by 95% isodose curve de-creased below 95%, respectively.

Conclusions: There were significant changes in targets during fractional radiotherapy for esophageal cancer which result in un-certainties of radiotherapeutic implementation.

Author Disclosure: X. Lu, None; B. Song, None; J. Qian, None; J. Huan, None; Y. Tian, None.

3144 In Vivo Dosimetry Analysis of Thyroid Gland Dose in Breast Cancer Patients with Supraclavicular Lymph

Node Irradiation

L. Peres1, M. L. Reisner1,2, C. L. P. Maurıcio3, H. Salmon2, P. C. V. Canary1

1Hospital Universitario Clementino Fraga Filho, Rio de Janeiro, Brazil, 2COI- Clınicas Oncologicas Integradas, Rio deJaneiro, Brazil, 3IRD- Instituto de Radioprotcao e Dosimetria, Rio de Janeiro, Brazil

Purpose/Objective(s): The recent advances in diagnosis and treatment of breast cancer have resulted in an increasing num-ber of long-term survivors. However, this population has suffered the consequences of breast cancer treatment, which usu-ally involves radiotherapy. Moreover, recent studies have shown the value of supraclavicular lymph nodes irradiation, evenwith only one positive axillar lymph node. Since a portion of the thyroid gland may also be included in the treatment fields,hypothyroidism, which has already been described as a well-known phenomenon following irradiation for Hodgkin’s dis-ease and head and neck tumors, should be considered a potential late complication of breast cancer radiotherapy. In one ofthe few studies found in literature, Reinertsen observed the prevalence of 18% of hypothyroidism in 403 patients submittedto breast radiotherapy, compared to 6% in the general population. The total dose received by the gland may play a majorrole in the incidence of hypothyroidism. Constin found hypothyroidism in 17% of children who received doses below 26Gy to the thyroid, compared to 78% who received more than 26 Gy, in a study of children treated for group treated forHodgkin’s disease.

Materials/Methods: Eighteen women eligible for breast and supraclavicular radiation were evaluated in order to quantify the ab-sorbed dose of the thyroid parenchyma. Three lithium fluoride TLD-100 thermoluminescent dosimeters (TLDs) measuring 3 mm x3 mm x 1 mm were used for dose measurement and positioned on the right and left lobes and the isthmus, and each patient wassubmitted to three measurements. The treatment planning was based on transverse CT images using a commercial treatment plan-ning system, consisting in a field arrangement of an anterior supraclavicular and two tangential fields. The cranial supraclavicularedge of the target volume was 1 cm below the larynx, whereas the medial edge was defined 1 cm lateral to the trachea down to thesternoclavicular junction. Photons of 6 MV were used for all treatment fields, and 50 Gy in 25 fractions were prescribed at 3cmdepth.

Results: The mean maximum dose observed in the entire gland was 605cGy, varying between 2.48% and 35% of the prescribeddose. The ipsilateral and the contralateral thyroid lobe, as well as the isthmus received a mean dose of 593cGy, 296cGy and 249cGyrespectively, which corresponds to 11.8%, 5.9% and 4.9% of the prescribed dose.

Conclusions: Despite the fact that the measured values were below the total dose of 26 Gy, the thyroid gland dose washigher than expected, in some cases reaching almost 35% of the prescribed dose. Hypothyroidism following breast