Stomach cancer risk following radiotherapy for testicular cancer.

Abstract

4536 Background: Testicular cancer (TC) is a highly curable malignancy occurring most commonly among men aged 15-34 years. Survivors are at increased risk for adverse late effects of therapy. Previous studies have reported more than 4-fold risks of stomach cancer after TC, although the potential role of radiotherapy and chemotherapy for TC in these associations is unclear. Methods: We evaluated stomach cancer risk in an international cohort of 23,982 men diagnosed with TC during 1959-1987. Using detailed radiotherapy records, doses to the stomach tumor location were estimated for 92 stomach cancer patients and 180 individually matched controls. Chemotherapy drugs and doses also were recorded. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression. Results: Fifty-seven percent of patients with stomach cancer were diagnosed with TC before age 40 years, 65% had seminoma, 95% had stage I or II disease, and 37% were diagnosed with stomach cancer ≥20 years after TC diagnosis. Patients who received radiotherapy [87 (95%) cases, 151 (84%) controls] had a 5.9-fold (95%CI 1.6-21.3) increased risk of stomach cancer compared with patients who did not receive radiotherapy. Risk increased with increasing radiation dose to the stomach (P-trend<0.001), with ORs of 3.6 (95%CI 1.3-10.6), 4.4 (1.2-16.4) and 13.3 (2.5-70.0) after 20-39.9 Gy, 40-49.9 Gy, and ≥50 Gy radiation to the stomach, respectively, compared with <10 Gy. Radiation-related stomach cancer risk did not vary by calendar year of treatment, age at exposure, or TC histology. The OR for having received any chemotherapy was 1.3 (14 cases, 23 controls, 95% CI 0.6-2.8). Stomach cancer risk was not significantly elevated among patients given cisplatin-based chemotherapy (7 cases, 10 controls, OR=1.7, 95% CI 0.6-5.1). Conclusions: Patients administered radiotherapy for TC in the past are at increased risk of developing stomach cancer, particularly those who received ≥20 Gy to the stomach. The study results warrant consideration in radiation risk assessment and long-term follow-up. Future studies should further investigate a possible role for chemotherapy in stomach cancer risk.