Second primary cancer risk in cervical cancer patients after definitive radiotherapy: a nationwide population-based study

Background: Although radiotherapy (RT) is an important treatment modality for cervical cancer, it can cause cancer. However, the risk of second primary cancer (SPC) tends to be ignored during RT for cervical cancer. We analyzed the prevalence and incidence patterns of SPC in cervical cancer patients that underwent definitive RT. Materials and Methods: The insurance claims data of cervical cancer patients that underwent definitive RT from 2007 to 2012 were analyzed. Standardized incidence ratios (SIRs) were used to estimate the relative risks of SPC. In addition, odds ratios were estimated by unconditional Poisson regression and adjusted for age at cervical cancer diagnosis, chemotherapy, and comorbidities. Results: Median patient age was 59.4 years. SIRs for bladder, ovary, and uterine cancer were 6.72 (95% confidence intervals (CI) 3.36–12.03, p < 0.001), 7.12 (95% CI 4.22–11.25, p < 0.0001), and 8.44 (95% CI 5.08–13.18, p < 0.001), respectively. The SIRs of all organs in the pelvic irradiation field were significantly increased. SIRs for breast and stomach cancer were 0.5 (95% CI 0.22–0.99, p = 0.0441) and 0.8 (95% CI 0.43–1.37, p = 0.5331), respectively. SIRs were not affected by chemotherapy, age, or comorbidities. Conclusion: RT increases the incidence of SPC in cervical cancer patients. In particular, SPC rates of organs in the irradiation field were higher than those of organs outside the irradiation field. If SPC risk were quantified with respect to irradiation dose, it could be utilized in clinical practice.