Radioiodine Has Small Benefit in Papillary Thyroid Cancer

Radioactive iodine appears to confer a small survival benefit in patients with papillary thyroid carcinoma (PTC), according to results presented at the 84th Annual Meeting of the American Thyroid Association.

The retrospective study, which included data from 284,635 patients, found that almost half of the patients underwent radioactive iodine therapy. Researchers noted that there was a small but statistically significant survival benefit regardless of tumor size.  This held true even after correcting for disease severity, demographics and extent of surgery.

“Most studies have not shown a survival advantage with radioiodine ablation, especially in small papillary thyroid cancers confined to the thyroid gland. In our study, a statistically significant survival advantage was found at 10 years for all tumor sizes and risk groups. This is probably due to the large number of patients in our study,” said study investigator Paritosh Suman, MD, of the North Shore University Health System in Evanston, Illinois.

In this study, all the patients had been treated for up to 13 years (mean follow-up, 7 years) and were placed in four categories based on their tumor size (≤10 mm; 11 mm to 20 mm; 21 mm to 40 mm; and >40 mm maximum diameter).

The researchers used Kaplan-Meier curves to analyze the use of radioactive iodine for each group, and they compared radioactive iodine therapy with no radioactive iodine therapy. After correcting for clinicopathologic, demographic and socioeconomic variables, they found radioactive iodine therapy was utilized in 47% of all PTC cases. However, there was a trend toward higher percentages for larger tumors (29% for tumors ≤10 mm vs. 58% for tumors >40 mm; P<.001).

The investigators concluded that radioactive iodine may be associated with a survival benefit in all tumor size categories, even after correcting for age, gender, tumor grade and surgeries. There also appeared to be a survival benefit after correcting for tumor-node-metastasis stage, insurance status, hormone suppression and presence of positive margins, positive lymph nodes and distant metastases.

The benefit of radioactive iodine therapy appeared to vary with tumor size. The researchers found HRs of 0.73 (P<.001) for tumors ≤10 mm in size; 0.82 (P=.04) for tumors ranging from 11 mm to 20 mm in size; 0.63 (P<.001) for tumors between 21 mm and 40 mm in size; and 0.62 (P=.001) for tumors >40 mm in size.

“This study shows there is a statistically significant benefit from radioiodine treatment of patients with papillary thyroid cancer.  Further study is needed to define which of these patients will achieve a more meaningful clinical benefit,” Dr. Suman told Endocrinology Advisor. 

“Radioiodine can improve patient survival.  Clinicians must consider all patient and tumor factors when deciding if their patient with papillary thyroid cancer will have a real benefit from radioiodine therapy.”

PTC is associated with excellent overall outcomes; however, the initial standard regimens call for surgical resection with the possible addition of radioactive iodine for those tumors believed to have a higher risk for recurrence.

There has been controversy about the actual clinical benefit of radioactive iodine for smaller tumors, though, especially those 10 mm or less.   

“We plan to evaluate as many patient and tumor factors as possible to determine which patients will have a sufficient benefit to warrant treatment that outweighs the risks and expense of this therapy,” said Dr. Suman. 

“We hope to further define the survival advantage of radioiodine for particular patients so an informed decision can be made by both the physician and patient on whether the expected survival benefit is worthwhile for them.”

Reference

1. Boone D et al. Oral Abstract 15. Presented at: American Thyroid Association (ATA) 84th Annual Meeting; Oct. 29-Nov. 2, 2014; Coronado, Calif.