Technical Progress and Role of

External RT in Thyroid Cancer

Yong Chan Ahn, MD/PhD Dept. of Radiation Oncology

SMC/SKKU SOM

In Treating Thyroid Cancer…

• Role of ERT has been proven in adjuvant,

salvage, as well as palliative settings.

• ERT, however, has been under-used than it

is needed, mainly in fear of annoying side

effects.

• With technical progress in ERT (IMRT,

IGRT) patients could get more benefit.

1. Is ERT effective in thyroid cancer?

2. What are indications of ERT?

3. What are problems of ERT?

4. Can new RT techniques be answer?

Case

• *** (F/76)

• CC: swallowing discomfort, hoarseness

Definitive high dose ERT alone

’09/3/31~5/28: 70 Gy/35 fractions by 3D conformal RT

’11/4/1 ’09/3/17

’11/10/11 ’09/3/20

1. Is ERT effective in thyroid cancer?

2. What are indications of ERT?

3. What are problems of ERT?

4. Can new RT techniques be answer?

IJROBP (2002)

• 1,057 DTC patients @ QEH (1960~1997)

842 patients (79.7%) had PTC

215 patients (20.3%) had FTC

• ERT (60 Gy/30 Fx’s) to thyroid bed and lymphatics if

gross LR disease in neck, extensive extrathyroidal

extension, extensive LN metastases

Summary @ QEH

• ERT reduced LR failure risk.

• In 124 patients with gross

residual improved LR control

rate by ERT (56.2% vs 24%,

p=0.0019)

• ERT to improve LR control is

indicated in patients with

gross postoperative residual

disease.

Clinical Endocrinology (2005)

• 729 DTC patients @ PMH (1958~1998)

’58~’71

(127)

’72~’85

(250)

’86~’98

(352)

Total

(729)

RAI Yes 59 (46%) 159 (64%) 310 (88%) 528 (72%)

No 68 (54%) 91 (36%) 42 (12%) 201 (28%)

RT Yes 71 (56%) 113 (45%) 134 (38%) 318 (44%)

No 56 (44%) 137 (55%) 218 (62%) 411 (56%)

Surgery Total 16 (13%) 95 (38%) 294 (84%) 405 (56%)

Subtotal 40 (32%) 61 (24%) 21 (6%) 122 (17%)

Lob 53 (42%) 86 (34%) 25 (7%) 164 (23%)

Summary @ PMH

• ERT improved LRFR

and CSS in high-risk

patients.

J Clin Endocrinol Metab (2011)

• Established role of EBRT in DTC:

• In adjuvant setting: extensive ETE, repeated cervical

nodal recurrence

• In definitive setting: local recurrence requiring

extensive ablative surgery

• Careful selection of high-risk patients is required.

EBRT in DTC • American Thyroid

Association guideline:

– >45 years

– Grossly visible ETE

– High likelihood of

microscopic residual

disease

– Gross residual tumor in

whom further surgery or

RAI would likely be

ineffective

– Sequence of EBRT and

RAI depends on gross

residual disease volume and

likelihood of RAI

responsiveness

• British Thyroid Association

guideline :

– Gross evidence of local

tumor invasion at surgery

– Presumed significant

macro- or microscopic

residual disease

– Residual tumor fails to

concentrate sufficient

amounts of radioiodine

– Extensive pT4 disease

– >60 years

– Extensive extra-nodal

spread even without evident

residual disease

EBRT in DTC • Medullary Thyroid Cancer:

– Further single institutional

data supports use of ERT

in improving local control

in highly selected patients

with MTC.

– However, ERT should be

reserved only in patients at

high risk of devastating

cervical recurrence

requiring extensive

ablative surgery.

• Anaplastic Thyroid Cancer:

– Extremely poor outcome.

– Improved local control

with concurrent ERT

(hyper-fractionation) and

taxanes.

ERT as Palliative Tx

• Symptomatic skeletal metastases

• Brain metastases

• Hepatic metastases

• For relief of pressure symptoms by soft tissue

tumor in vital areas -- SVC syndrome

• Recurrent/metastatic tumor following RAI

• * ATC, MTC

1. Is ERT effective in thyroid cancer?

2. What are indications of ERT?

3. What are problems of ERT?

4. Can new RT techniques be answer?

Disadvantages of ERT

• Loco-regional Tx modality

• Not a selective Tx modality

• Long Tx duration (5~6 weeks)

• Dose-response relationship?

– Normal tissue tolerance limit have

been usually applied (50~60 Gy)

• Optimal RT target volume?

– Tumor bed + entire neck +/- upper mediastinum

Common Side Effects of ERT

• Aerodigestive track:

– Swallowing discomfort, pain, voice change, dyspnea,

cough, sputum

• Skin and soft tissue:

– Dermatitis, lymphedema, fibrosis, joint stiffness, soft

tissue necrosis

• Glandular structures:

– Dry mouth (dental caries), dry eye

• Skeletal system:

– Osteonecrosis, chondronecrosis

• Others:

– Fatigue, anorexia, nausea, second cancer

1. Is ERT effective in thyroid cancer?

2. What are indications of ERT?

3. What are problems of ERT?

4. Can new RT techniques be answer?

From 2-D to 3-D

Intensity Modulated RT

2D

3D

IMRT

Image Guided RT

Individualized

Customized

Adaptive

New RT Techniques

Precise

Accurate

Reliable

Therapeutic Ratio

New RT Techniques

• Intensity Modulated RT (IMRT)

– LINAC-based: step & shoot;

sliding window; volumetric arc

– Helical Tomotherapy

• Image-guide RT (IGRT)

• Stereotactic Body RT (SBRT)

RT Technique

• Combination of IMRT and IGRT may be

beneficial in reducing toxicity and improving

local control.

• IMRT and IGRT should ideally be employed

when treating thyroid cancer with EBRT.

In Treating Thyroid Cancer…

• Role of ERT has been proven in adjuvant,

salvage, as well as palliative settings.

• ERT, however, has been under-used than it

is needed, mainly in fear of annoying side

effects.

• With technical progress in ERT (IMRT,

IGRT) patients could get more benefit.