Fifty-Year-Follow-up Results Compared with Shorter Follow-up of Breast Cancer Patients Undergoing Radical Mastectomy with or without Adjuvant Radiotherapy

Background: To evaluate the effect of follow-up length on the outcome of breast cancer patients, we compared the 50- and 25-year follow-up results in terms of cure rate, overall mortality and mortalities from breast cancer, second cancer, and benign diseases. Methods: 763 patients treated for breast cancer between February 1953 and September 1976, were followed up until December 2014. They were divided into two cohorts; earlier cohort exclusively underwent radical mastectomy plus adjuvant radiotherapy, while later cohort had radical mastectomy alone. Assuming that in all patients follow-up was terminated at 50 or 25 years after diagnosis, likelihood ratio test and stratified Log-rank tests were performed to evaluate the differences in cure rate and overall survival between the two cohorts. Results: During the 50 years, radical mastectomy alone compared with radical mastectomy plus adjuvant radiotherapy is associated with a significantly higher cure rate, and higher survivals regardless of whether the death was from breast cancer, second cancer, benign causes or any causes. However, if follow-up information is limited to 25 years, the advantage of radical mastectomy alone is partly offset and the survival difference between the two cohorts becomes less significant. Conclusion: Radiotherapy to breast cancer may adversely affect not only mortality from breast cancer, but mortalities unrelated to breast cancer. Since such deaths occur later, they may fail to be detected unless follow-up is long enough. Thus, deleterious effects of radiotherapy may be underestimated. Exceedingly long follow-up is required to accurately estimate the cure rate and the long-term effect of radiotherapy.