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Second primary malignancy risk after radiotherapy in rectal cancer survivors
Ti-Hao Wang1, Chia-Jen Liu2, Tze-Fan Chao3
1Department of Radiation Oncology, China Medical University Hospital, Taichung 40447, Taiwan.
Aim:
To investigate second primary malignancy (SPM) risk after radiotherapy in rectal cancer survivors.
Methods:
We used Taiwan's National Health Insurance Research Database to identify rectal cancer patients between 1996 and 2011. Surgery-alone, preoperative short course, preoperative long course, and post-operative radiotherapy groups were defined. The overall and site-specific SPM incidence rates were compared among the radiotherapy groups by multivariate Cox regression, taking chemotherapy and comorbidities into account. Sensitivity tests were performed for attained-year adjustment and long-term survivors analysis.
Results:
A total of 28220 patients were analyzed. The 10-year cumulative SPM incidence was 7.8% [95% confidence interval (CI): 7.2%-8.2%] using a competing risk model. The most common sites of SPM were the lung, liver, and prostate. Radiotherapy was not associated with increased SPM risk in multi-variate Cox model (hazard ratio = 1.05, 95%CI: 0.91-1.21, P = 0.494). The SPM hazard remained unchanged in 10-year-survivors. In addition, no SPM risk difference was found between the preoperative radiotherapy and postoperative radiotherapy groups.
Conclusion:
In this large population-based cohort study, we demonstrated that radiotherapy had no increase in SPM.
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