ESPE Yearbook of Paediatric Endocrinology

Brief Summary: This retrospective study evaluated the risk and clinicopathological features of second primary thyroid cancer (SPTC) in cancer survivors. The Surveillance, Epidemiology, and End Results (SEER) Program collected cancer incidence and mortality data from 8 population-based registries. They identified 7066 patients with SPTC and 83,113 patients with primary thyroid cancer (TC). The standardized incidence ratio (SIR) of SPTC in cancer survivors was higher than in the general population (1.51 vs 0.94/10,000).

The risk of SPTC was associated with some first tumors (acute lymphocytic leukemia, Hodgkin’s lymphoma, salivary gland cancer, kidney cancer) and radiotherapy/chemotherapy before age 35 years. Patients with SPTC were younger (49.6 years vs 64), with a higher proportion of males (34% vs 25%). The mean latency between first tumor and SPTC was 7.6 years, but differed by type of first tumor. Primary lung and bronchus tumors were associated with early SPTC, while median latency between Hodgkin’s lymphoma and SPTCs was 16 years. The most common pathological type was papillary carcinoma in both groups, with a higher percentage of histological grades 3/4 in cancer survivors (23% vs. 15%). No difference in survival rate was found between SPTC and primary TC, after adjusting for other factors.

The present study compared demographics and clinicopathological characteristics of primary TC and SPTC in a very large dataset. There was an increasing trend of thyroid cancer diagnosis with time, probably due to improvements in detection methods as well as more regular surveillance. The study showed for the first time that first tumor survivors who received chemotherapy (not only radiotherapy) before age 35 years had a significantly increased incidence of thyroid cancer. Limitations of the study are its retrospective design; it was impossible to verify missing information from the SEER database, and data on primary tumor treatment were limited to ‘yes/no’ radiotherapy and chemotherapy. However, these data, including the latency between the first tumor diagnosis and SPTC, should contribute to improved surveillance strategies.