Assessing the association between cycles of fertility treatments with gonadotropins and cancer risk.

10599 Background: Fertility treatments such as in vitro fertilization (IVF) and controlled ovarian hyperstimulation relies on exogenous hormones known as gonadotropins that directly stimulate ovarian activity. Concerns have arisen regarding the increased risk of hormone-sensitive cancer development due to repeated hormonal stimulation. The literature regarding this risk is ambiguous. We aimed to assess the association between the number of fertility treatments with gonadotropins (FT-GT) cycles and cancer risk in a large national HMO database. Methods: The Clalit Health Services database was analyzed between 2003-2013 to identify females who underwent FT-GT along with matched controls by age, ethnicity and socioeconomic status. FT-GT cycles were identified through the use of gonadotropins. Controls were matched 4:1 with untreated females. Patients were grouped based on number of FT-GT cycles being 1–4, 5–7, or ≥8. Cancer risk analysis focused on breast, colon, thyroid, stomach and pancreas, as well as any detectable cancer. We performed a separate sub-analysis of women who received ≥10 FT-GT cycles. Results: A total of 178, 637 patients were analyzed- 39,068 received FT-GT; 24,716 underwent 1–4 cycles; 7,774 underwent 5–7 cycles; and 6,578 received ≥8 cycles. For the separate sub-analysis, 3,949 women received ≥ 10 cycles. The median follow-up was 12.6 years. The risk of breast cancer increased with the number of FT-GT cycles, with the highest risk observed in patients receiving ≥8 cycles (HR = 1.67, 95% CI: 1.22-2.27), followed by 5-7 cycles (HR = 1.42, 95% CI: 1.07-1.89), and 1-4 cycles (HR = 1.34, 95% CI: 1.15-1.56), when adjusting for hypothyroidism. When analyzing the ≥ 10 cycle sub-group, the hazard ratio for breast cancer reaches 1.79 (95% CI: 1.19-2.70). There was no correlation between FT-GT cycle number and colon, stomach or pancreatic cancer, or any other detected cancer. Conclusions: It appears that females receiving FT-GT are at a higher risk for breast cancer from the first cycle. The risk of breast cancer increases with the number of FT-GT cycles. None of the other cancers analyzed showed any significant cancer risk associated with FT-GT.