Purpose: To assess the risk of esophageal cancer as second cancer among breast-cancer patients treated with radiotherapy.
Methods and materials: The records of the Finnish Cancer Registry from 1953 to 2000 were used to assess the risk of esophageal cancer as second cancer among 75,849 breast-cancer patients. Patients were treated with surgery (n = 33,672), radiotherapy (n = 35,057), chemotherapy and radiotherapy (n = 4673), or chemotherapy (n = 2,447). The risk of a new primary cancer was expressed as standardized incidence ratio (SIR), defined as the ratio of observed to expected cases.
Results: By the end of 2000, the number of observed cases esophageal cancers was 80 vs. 72 expected cases (standardized incidence ratio (SIR) = 1.1, 95% Confidence Interval (CI) = 0.9 to 1.5). Among patients followed for 15 years and treated with radiotherapy, the SIR for esophageal cancer was 2.3 (95% CI = 1.4 to 5.4). No increase in risk was seen for patients treated without radiotherapy. The risk of esophageal cancer was increased among patients diagnosed during 1953 to 1974, although age at the treatment did not have marked effect on the risk estimate.
Conclusion: Increased risk of second cancer in the esophagus was observed for breast-cancer patients in Finland, especially among patients with over 15 years of follow-up and treated in the earliest period, which may relate to the type of radiotherapy.