7 -- Thyroid Endocrine Board

7/31/2019 7 -- Thyroid Endocrine Board

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ROLE OF EXTERNALBEAM RADIATION IN

THYROIDMALIGNANCIES

Faisal Vali, MSc, MD, RadiationOncology


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Epidemiology

Lifetime risk of thyroid malignancy < 1%

~56,000 new cases, ~1,800 deaths(~3.2%)

Btw 15-24 years, it is 7.5 to 10% of

all cancers

Peak incidence is at 49 years

NCCN v2.2012


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Thyroid Malignancies

Well Differentiated Thyroid Cancer(WDTC): 94%

Papillary 80%

Follicular 11%

Hurthle 3%Hundahl SA, Fleming ID, Fremgen AM, Menck HR. A National Cancer Data Base report on 53,856 cases ofthyroid carcinoma treated in the U.S., 1985-1995 [see comments]. Cancer 1998;83:2638-2648. Available at:http://www.ncbi.nlm.nih.gov/pubmed/9874472.


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Thyroid Malignancies

Medullary Thyroid Cancer : 4%

Anaplastic Thyroid Cancer : 2%

Thyroid Lymphoma (


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Survival Data

10 y OS Differentiated Thyroid CancerPapillary: 93%

Follicular: 85%

Hurthle: 76% Anaplastic : MS of 3-7 mo, 5y 8%

Medullary: 10 y OS @ 75%

Thyroid Lymphoma: 5y OS: 64%


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Staging


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Staging

Size basedT1 2cm

T2 4cm

T3 > 4cm intrathyroidOR any size w minimal ETE: perithyroid soft

tissues

T4 a = ETE: larynx, esophagus, or

Recurrent LaryngealT4 b = ETE: prevertebral fascia, encases

carotid


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Staging


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External Beam RT


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I-131is radioactive DECAY

I-131: Radioactive Decay of anunstable nucleus release electronsand photons


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X-RayIrradiation

EBRT: Generation of X-rays byslowing down acceleratedelectrons, which then releaseelectrons in matter

70%

30%


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Rationale for EBRT

External beam radiotherapy carries thepotential for improving locoregional

disease control

Locoregional : primary site and regionalnodes (which is where the radiation isaimed)


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Rationale for EBRT


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EBRT in WellDifferentiated TCa


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Management of DifferentiatedThyroid Cancer

No data from prospective randomizedtrials for any modality

Most data is from large non-randomizedpatient cohorts (prospective orretrospective)

Treatment of choice is Surgery

Adjuvant Tx: radioiodine and thyroxine


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Papillary/Follicular/Hurthle


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Data for EBRT (MDACC)

Retrospective: 1996 2005 of 131 pts

High Risk: Hurthle cell, tall cell, clear

cell, or poor

Median F/U: 38 months (3.5 years)

4y LRFS = 79%, DSS = 76%, OS = 73%

2% clinically significant toxicity with


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Adjuvant EBRTConsideration

Always consider EBRT, if poor I-131 uptake

If 50y AND T4 dz with R1/R2 resections (microscopic residual dz)

If < 50 y AND T4b or, Extensive T4a + poorhistology (hurthle, tall, etc.)

If Lymph Node positive & Extensive

Extracapsular extension or V. High NodalRatio (>80-90%)

Any recurrence (in thyroid bed or neck):EBRT should be considered followingsurgery and radioiodine


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Radiation Details (WDT)

Target: Thyroid bed & Level 2-6 nodes(consider 7)

Radiation Dose:66 Gy in 33 fractions to Higher Risk Areas

56 Gy in 33 fractions to lower risk CTV.


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K&A 2011


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EBRT in Anaplastic TCa


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Anaplastic

One of the most lethal of all cancers :15-50% present with mets (Lungs 90%,15% bone, 5% CNS)

Surgical Resection is rarely possible

Concentrate RAI very infrequently

EBRT Rationale is to maximize local

control and prevent death from


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Anaplastic


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Radiation Details

Target: thyroid bed and the adjacentlymph nodes (avoid entire neck ormediastinum)

If KPS 60 & M0 60 Gy in 40fractions, BID Taxane

If KPS < 60 palliative 20 Gy in 5fractions, may repeat in 4 weeks if thereis mild response


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EBRT in Medullary Cancer


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EBRT i M d ll Th id


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EBRT in Medullary ThyroidCancer

No role for I-131

If resection is incomplete, calcitoninremains elevated, T4 dz or recurrence

consider EBRT

M d ll Th id C RT


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Medullary Thyroid Cancer RTDetails

TARGET: thyroid bed, residual dz,cervical nodes

56 Gy in 33 fractions to the cervicallymph nodes

66 Gy in 33 fractions to potential

residual disease


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EBRT in ThyroidLymphoma


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Thyroid Lymphoma

Diffuse Large B Cell (aggressive) 70% >MALT(indolent) vs 30%

Staged according to Lymphoma

DLBCL: Chemo (R-CHOP) + EBRT

MALT: RT alone

Hashimotos: risk is 60 times higher


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Thyroid Lymphoma

35 Gy in 20 fractions to encompass thethyroid, neck nodes bilaterally, and

superior mediastinal nodes

If not indolent, DLBCL R-CHOP x 3

cycles + RT 4 weeks later


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Metastastases


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Bone Metastases


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Bone Metastases(Uptodate)

Bone mets (3% remission post RAI) dontrespond as well to radioiodine as Lung

mets do

All patients with symptomatic bone metsshould be referred for EBRT (40-50Gy)


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Toxicities from EBRT


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Potential Acute Toxicities

Moderate skin erythema

Dry desquamation and, rarely, moist

desquamation

Mucositis of the esophagus, trachea, and

larynx, subsides within 2-4 weeks (mayrequire a soft diet and analgesics)


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Long Term Toxicity

Well-planned radiotherapy treatmentregimens rarely have serious long-termcomplications.

Most Common: skin telangiectasias andskin pigmentation.

Esophageal stenosis is rare and Trachealstenosis is extremely rare.


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Conclusions


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Treatment Paradigms

WDTCa = Surgery Radioactive Iodine EBRT TSH suppression

Anaplastic = Local Control is importantto QOLhyperfractionated EBRT + taxane based

chemo

Medullary = Surgery (no RAI, no TSHsuppression) EBRT


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Conclusions

No prospective randomized trials forthyroid cancer

Role for EBRT is still being defined

There is retrospective data that suggestsit can be done safely and effectively,

especially with IMRT


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Refer to RadOnc if any

Unresectable tumors/Gross Positivemargins

High risk histologies: tall cell, columnar,

hurthle Poor RadioIodine uptake by tumor

Extrathyroidal extension at time of

surgery Large Nodal Ratio and/or Extensive ECE

Palliation for symptomatic recurrenttumor or mets


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Questions??

Thank you!

7 -- Thyroid Endocrine Board

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