Does RAIT increase the risk of second primary malignancies in patients with PTC?

In patients with papillary thyroid cancer (PTC), radioactive iodine therapy (RAIT) does not appear to increase the risk of a second primary malignancy (SPM), reports a study. On the other hand, age and personal or family history of cancer are predictive of SPM in this population.

The authors performed a retrospective review of PTC patients who underwent thyroid surgery at a single institution from January 2007 to January 2011 to explore the incidence of SPM, demographic risk factors, and association with RAIT.

A total of 528 patients were included, of whom 40 (7.6 percent) had a diagnosis of SPM over a median follow-up of 9.3 years. The standardized ratio was 1.3 using demographic-adjusted SEER data, and the median time to SPM diagnosis was 4.0 years. The most common SPM was breast cancer, which occurred in 12 patients (30 percent).

RAIT use and dose showed no significant association with SPM. No significant association was also observed between SPM and mortality (6.3 percent SPM+ vs 3.1 percent SPM-; p=0.300).

SPM was associated with older age (median 56.5 vs 49.0 years; p=0.004), prior personal history of cancer (22.5 percent vs 11.3 percent; p=0.036), and family history of cancer (70 percent vs 42.8 percent; p<0.001), but none of these were independent risk factors.

“PTC patients develop nonthyroid SPM at a rate higher than the general population,” the authors said.