Radioactive Iodine for Thyroid Cancer


This is a detailed section on the use of radioactive iodine for thyroid cancer

Radioactive iodine is one of the many steps in treating thyroid cancer also called thyroid ablation or thyroid cancer treatment. Radioactive iodine ablation (RAI) is indicated when treating differentiated thyroid cancer that has spread beyond the thyroid. Thyroid cancer can be staged with the AJCC/UICC or with the NTCTCSG system which can predict disease mortality and help to plan for possible radioactive iodine. So far, there is not a perfect staging system for thyroid cancer. Ideally the best staging system would:
1) provide common descriptors that facilitate communication among physicians and institutions regarding individual patients and patient cohorts
2) allow physicians to estimate the prognosis for any given patient as well as the expected benefit from therapies
3) permit appropriate stratification for the design and analysis of retrospective clinical studies and prospective clinical trials

CHAT WITH US SCHEDULE AN APPOINTMENT
The NTCTCSG system differs from the AJCC system in that some patients with AJCC stage I disease are advanced to higher stages in the NTCTCSG system. This difference can affect treatment consideration s in up to 50% of patients with differentiated thyroid cancer. As of 2010, the effect of radioiodine therapy on patients with NTCTCSG-defined stage I disease is neutral and not associated with an increase or decrease in survival, The implication of this finding is that if radioiodine therapy is deemed appropriate to improve accuracy of follow up by thyroglobulin monitoring and radioiodine scanning in certain patients with stage I, the 2010 data shows no detrimental effect of adjuvant radioiodine therapy on patient survivial.


Following a low iodine diet during the 2-3 week period prior to radioactive iodine therapy will make the treatment more effective. This treatment uses radioactive iodine (131I) to destroy leftover microscopic thyroid cancer cells as well as any normal thyroid tissue that might remain after surgery. Destroying these cells makes it easier for doctors to follow patients for signs of thyroid cancer recurrence. Radioactive iodine treatment is used in most patients with differentiated papillary, follicular and Hurthle cell thyroid cancers. There are specific precautions to take after radioactive iodine is given. There are common side effects of radioactive iodine.



Suggested guidelines per the 2010 American Thyroid Association Consensus
  • RAI ablation is recommended for all patients with known distant metastases, gross extrathyroidal extension of the tumor regardless of tumor size, or primary tumor size >4 cm even in the absence of other higher risk features
  • RAI ablation is recommended for selected patients with 1–4 cm thyroid cancers confined to the thyroid, who have documented lymph node metastases, or other higher risk features (see preceding paragraphs) when the combination of age, tumor size, lymph node status, and individual histology predicts an intermediate to high risk of recurrence or death from thyroid cancer
  • RAI ablation is not recommended for patients with unifocal cancer <1 cm without other higher risk features 
  • RAI ablation is not recommended for patients with multifocal cancer when all foci are <1 cm in the absence other higher risk features 


This is the National Thyroid Cancer Treatment Cooperative Study Group (NTCTCSG) staging system for thyroid cancer


The Disease Stage Assigned to a Patient Is the Highest Stage Determined by These Clinicopathologic Features
  Tumor type
Papillary carcinoma Follicular carcinoma
 <45 yo  >45 yo <45 yo >45 yo
rimary tumor size (cm)        
  <1 I I I II
  1-4 I II I III
  >4 II III II III
Primary tumor description        
  Microscopic multifocal I II I III
  Macroscopic multifocal or macroscopic tumor capsule invasion I II II III
  Microscopic extraglandular invasion I II I III
  Macroscopic extraglandular invasion II III II III
  Poor differentiation NA NA III III
Metastases        
  Cervical lymph node metastases I III I III
  Extracervical lymph node metastases III IV III IV
  Medullary carcinoma
  1. NA: not applicable.

  2. All anaplastic carcinomas are Stage IV.

C-cell hyperplasia I
Tumor size < 1 cm II
Tumor size ≥ 1 cm or positive cervical lymph nodes III
Extraglandular invasion or extracervical metastases IV


This is the NCI/American Joint Committee on Cancer (AJCC) staging system. 

 

 


 

 

Factors

Description

Decreased risk of death

Decreased risk of recurrence

May facilitate initial staging and follow-up

RAI ablation usually recommended

Strength of evidence

T1

1 cm or less, intrathyroidal or microscopic multifocal

No

No

Yes

No

E

 

1–2 cm, intrathyroidal

No

Conflicting dataa

Yes

Selective usea

I

T2

>2–4 cm, intrathyroidal

No

Conflicting dataa

Yes

Selective usea

C

T3

>4 cm

 

 

 

 

 

 

<45 years old

No

Conflicting dataa

Yes

Yes

B

 

≥45 years old

Yes

Yes

Yes

Yes

B

 

Any size, any age, minimal extrathyroidal extension

No

Inadequate dataa

Yes

Selective usea

I

T4

Any size with gross extrathyroidal extension

Yes

Yes

Yes

Yes

B

Nx,N0

No metastatic nodes documented

No

No

Yes

No

I

N1

<45 years old

No

Conflicting dataa

Yes

Selective usea

C

 

>45 years old

Conflicting data

Conflicting dataa

Yes

Selective usea

C

M1

Distant metastasis present

Yes

Yes

Yes

Yes

A

aBecause of either conflicting or inadequate data, the ATA guidelines cannot recommend either for or against RAI ablation for this entire subgroup. However, selected patients within this subgroup with higher risk features may benefit from RAI ablation (see modifying factors in the text).

several other histological features may place the patient at higher risk of local recurrence or metastases than would have been predicted by the AJCC staging system. These include worrisome histologic subtypes (such as tall cell, columnar, insular, and solid variants, as well as poorly differentiated thyroid cancer), the presence of intrathyroidal vascular invasion, or the finding of gross or microscopic multifocal disease. While many of these features have been associated with increased risk, there are inadequate data to determine whether RAI ablation has a benefit based on specific histologic findings, independent of tumor size, lymph node status, and the age of the patient. Therefore, while RAI ablation is not recommended for all patients with these higher risk histologic features, the presence of these features in combination with size of the tumor, lymph node status, and patient age may increase the risk of recurrence or metastatic spread to a degree that is high enough to warrant RAI ablation in selected patients. However, in the absence of data for most of these factors, clinical judgment must prevail in the decision-making process. For microscopic multifocal papillary cancer, when all foci are <1 cm, recent data suggest that RAI is of no benefit in preventing recurrence

Nonpapillary histologies (such as follicular thyroid cancer and Hürthle cell cancer) are generally regarded as higher risk tumors. Expert opinion supports the use of RAI in almost all of these cases. However, because of the excellent prognosis associated with surgical resection alone in small follicular thyroid cancers manifesting only capsular invasion (without vascular invasion (so-called “minimally invasive follicular cancer”), RAI ablation may not be required for all patients with this histological diagnosis



References:
Hay ID, Hutchinson ME, Gonzalez-Losada T, McIver B, Reinalda ME, Grant CS, Thompson GB, Sebo TJ, Goellner JR 2009 Papillary thyroid microcarcinoma: a study of 900 cases observed in a 60-year period. Surgery144:980–987
Ross DS, Litofsky D, Ain KB, Brierley JD, Cooper DS, Haugen BR, Jonklaas J, Ladenson PW, Magner J, Robbins J, Skarulis MC, Steward DL, Maxon HR, Sherman SI 2009 Recurrence after treatment of micropapillary thyroid cancer. Thyroid 19:1043–1048.
van Heerden JA, Hay ID, Goellner JR, Salomao D, Ebersold JR, Bergstralh EJ, Grant CS 1992 Follicular thyroid carcinoma with capsular invasion alone: a nonthreatening malignancy. Surgery. 112:1130–6.
Sherman SI et al. Prospective multi center study of thyroid carcinoma treatment: initial alaysis of staging and outcome
Butler et al. Thyroid Vol 20, pp 1423 - 1424 Nov 12 2010

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