Elsevier

Oral Oncology

Volume 49, Issue 7, July 2013, Pages 676-683
Oral Oncology

Selective use of RAI for ablation and adjuvant therapy after total thyroidectomy for differentiated thyroid cancer: A practical approach to clinical decision making

https://doi.org/10.1016/j.oraloncology.2013.03.444Get rights and content

Summary

Objectives: For the past 40 years, many clinicians have recommended RAI remnant ablation for essentially all differentiated thyroid cancer patients with a primary tumor size greater than 1.5 cm or with any evidence of even microscopic disease outside the thyroid capsule. This “one size fits all” approach exposes many low risk thyroid cancer patients to the risks of ionizing radiation with little potential benefit. Current thyroid cancer management guidelines call for a far more risk adapted approach to the selection of patients for post-operative RAI treatment. Materials and Methods: We will review the current selective use of RAI ablation recommendations and provide a practical approach to implementation of a risk adapted approach to post-operative RAI administration. Results and Conclusions: We will show how thoughtful integration of pre-operative, intra-operative, and post-operative clinico-pathologic factors allows the clinician to accurately identify patients most likely to benefit from RAI administration. This approach ensures that patients most likely to experience a clinical benefit are selected for RAI ablation while avoiding unnecessary exposure to ionizing radiation in the majority of low to intermediate risk thyroid cancer patients.

Section snippets

Risk adapted management of thyroid cancer

Since the 1970s, the need for RAI remnant ablation in the management of differentiated thyroid cancer was almost completely based on the size of the primary tumor (>1.5 cm) and the presence or absence of thyroid cancer outside the thyroid gland (extrathyroidal extension, lymph node involvement, distant metastases).1, 2] In addition, the practice of “sub-total thyroidectomy” left a remnant of thyroid tissue behind, making post-operative follow up with thyroglobulin difficult. Therefore, “remnant

Potential benefits of post-operative RAI ablation/adjuvant therapy

In a careful review of the published data, the ATA guidelines summarized the expected benefits of RAI ablation with regard to decreasing the risk of death, decreasing the risk of recurrence, and improving initial staging and follow-up for differentiated thyroid cancer patients based on the clinical factors used in AJCC/TNM staging (Table 1).7 To help delineate the potential benefits of the first dose of RAI (commonly referred to as RAI ablation), the functions of RAI were separated into (1)

ATA and NCCN guideline recommendations

With regard to specific treatment recommendations, both the ATA and NCCN guidelines provided the advice that “RAI ablation is usually recommended” in patients with large primary tumors regardless of age (>4 cm), and in patients with gross extrathyroidal extension, or distant metastases.7, 8 Furthermore, the ATA guidelines also recommended RAI ablation for “almost all” follicular and hurthle cell thyroid cancers because these histologies were deemed to be relatively high risk. Conversely, RAI

Our practical approach to patient selection

In our practice, rather than focusing exclusively on the size of the primary tumor and the extent of lymph node metastases, we find it more helpful to consider the series of questions presented in Fig. 1 in order to better define the potential benefit (or lack thereof) for each individual patient being considered for RAI ablation/adjuvant therapy (Fig. 1).

Oftentimes the answers to these questions rely on the same clinico-pathologic factors identified in the ATA and NCCN guidelines (T, N, M

Clinical indications for RAI ablation

Consistent with the ATA and NCCN guideline recommendations,7, 8 we routinely recommend RAI ablation for patients at high risk of recurrence, disease specific mortality or distant metastases (Table 3). Furthermore, we also recommend RAI ablation in specific clinical scenarios in which either the post-ablation RAI scan is needed for initial staging or an undetectable serum thyroglobulin is required during follow-up to identify recurrent disease that may not be adequately identified with neck

Clinical indications for observation rather than immediate RAI ablation

While it is critically important to define the indications for RAI ablation, it is equally as important to identify differentiated thyroid cancer patients that are very unlikely to obtain substantial benefit from an initial empiric dose of RAI after thyroidectomy. As described above, multiple clinical factors beyond simply the size of the primary tumor and extent of lymph node metastatic spread are critical components in the decision making process. In Table 4, we describe several clinical

Follow-up recommendations in patients not receiving RAI ablation

As can be seen from the discussion above, patients selected for follow-up without RAI ablation have been selected because the risk of clinically significant recurrence is low, the risk of distant metastases is low, the likelihood that the recurrent disease will be detected easily with serial Tg measurements and neck US is high, and the likelihood that salvage therapy will be very effective is high. As such, the follow-up paradigm will rely primarily on serial neck US and non-stimulated Tg

Summary

A risk adapted approach to the selection of patients for RAI ablation requires far more information than just the size of the primary tumor and knowing whether or not loco-regional lymph nodes are involved. By combining all of the information available from pre-operative evaluations, intra-operative findings, and post-operative evaluations, the clinician is able to estimate the risk of recurrence, risk of disease specific mortality, risk of having RAI avid distant metastases and the potential

Disclosure statement

RMT (consultant to Genzyme Corporation).

Conflict of interest statement

None declare

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