Second neoplasms in survivors of endometrial cancer: Impact of radiation therapy

ObjectiveTo evaluate the association of radiotherapy to subsequent second cancers in endometrial carcinoma survivors.MethodsSubjects with endometrial cancer as their first malignancy were identified from the Surveillance, Epidemiology and End Results (SEER) database from 1973 to 2004 and were divided into radiation (R) and No Radiation (NR) groups. Person years at risk (PYR), observed (O) and expected (E) counts and SIR (standardized incidence ratio) were determined. (%) increase in relative risk (RR) for R vs. NR group was calculated using Poisson regression. Absolute Excess Risk (AER) was ‘O’ minus ‘E’ per 10,000 PYRs.ResultsOf 90,502 subjects 31,643 (34.9%) were in R and 52,182 (57.6%) in NR. The radiation status of 6677 (7.3%) was unknown. In the R group 4203 developed second cancers vs. 5563 in NR group; relative risk for R group–1.25 (95% CI 1.20 to 1.29). A total of 17.11 excess tumors were observed in R group (AER). The relative risk increased with latency of exposure and peaked at (> 10 years), being 40% (p < 0.001). The statistically significant (%) increase in RR for individual organs was as follows: urinary bladder (124%), vagina (88%), vulva (83%), sarcoma (70%), colon and rectum (43%) and lung (29%).ConclusionIn the largest study reporting on association of radiotherapy to subsequent second neoplasms in endometrial cancer survivors, the increased risk of second cancers was most pronounced in the field of exposure and was affected by latency since exposure.