Background: Several case reports have suggested an association between radiation therapy for breast cancer and the subsequent occurrence of esophageal carcinomas.
Objective: To examine the association between radiation therapy for breast cancer and subsequent esophageal squamous-cell carcinomas and adenocarcinomas.
Design: Population-based retrospective cohort study.
Setting: Population-based U.S. cancer registries.
Patients: 220 806 women in whom breast cancer was diagnosed between 1 January 1973 and 31 December 1993; 1 216 853 person-years of follow-up.
Measurements: Age- and period-adjusted standardized incidence ratio as a measure of relative risk for the second primary cancer.
Results: In women who had received radiation therapy for breast cancer, the relative risk for esophageal squamous-cell carcinoma increased to 5.42 (95% CI, 2.33 to 10.68) and the relative risk for esophageal adenocarcinoma increased to 4.22 (CI, 0.47 to 15.25) 10 or more years after radiation therapy. No increased risk was seen for either type of carcinoma among patients with breast cancer who did not receive radiation therapy.
Conclusion: The risk for esophageal carcinoma is increased in women who receive radiation therapy for breast cancer.