Incidence and Risk of Second Primary Malignancies After Treatment for Papillary Thyroid Cancer: A Single Institution Study.

[OBJECTIVES] Papillary thyroid cancer (PTC) patients develop nonthyroid second primary malignancy (SPM) at a rate higher than the general population. We aimed to investigate the incidence of SPM, demographic risk factors, and relationship with RAIT among PTC patients.

[METHODS] A retrospective review was performed of PTC patients who underwent thyroid surgery at a single institution from 1/2007 to 1/2011.

[RESULTS] Of 528 patients, 40 (7.6%) were diagnosed with SPM (SPM+) over a median follow-up of 9.3 years. The standardized incidence ratio was 1.3 using demographic-adjusted SEER data. Median time to SPM diagnosis was 4.0 years (IQR 2.0, 6.7). Breast cancer was the most common SPM, occurring in 12 patients (30%). RAIT use and RAIT dose were not associated with SPM. There was no significant association between SPM and mortality (6.3% SPM+ vs. 3.1% SPM-, P =0.300). Older age (median 56.5 vs. 49.0 y, P =0.004), prior personal history of cancer (22.5% vs. 11.3%, P =0.036), and family history of cancer (70.0% vs. 42.8%, P <0.001) were associated with SPM+, but none were identified as independent risk factors.

[CONCLUSIONS] This study did not find any association between SPM and RAIT in PTC patients. Factors other than RAIT, such as age and personal or family history of cancer were associated with SPM risk in PTC patients.