Long-term follow-up of a randomised trial designed to determine the need for irradiation following conservative surgery for the treatment of invasive breast cancer.
Four hundred consecutive patients aged under 70 years diagnosed with a clinical T1 or T2 breast cancer were randomised to receive post-operative radiotherapy (n = 208) or not (n = 192), and monitored to record all local recurrences, distant recurrences and deaths for up to 20 years (median 13.7 years). All patients were treated by wide local excision and adjuvant therapy [estrogen receptor (ER) positive: tamoxifen; ER negative: CMF chemotherapy]. Kaplan-Meier and log-rank test methods were used to estimate and compare survival and recurrence. The 20-year Kaplan-Meier rates for local breast recurrence were 28.6% [95% confidence interval (CI) 19.6% to 37.6%] for radiotherapy and 49.8% (95% CI 40.8% to 58.9%). There was no significant difference between the two groups with regard to disease-free or overall survival. The hazard ratio for death among women who received radiation, as compared with those that did not, was 0.91 (95% CI 0.64-1.28; P = 0.59). Therefore, post-operative radiotherapy produced a clear-cut reduction in locoregional recurrence 0.45 (0.31-0.64; P = 0.0001), but did not influence the incidence of distant metastases or time of death. However, of the 119 patients who had a local recurrence, 51 (42.8%) had a distant recurrence, whereas of the 281 without local recurrence only 59 (21%) ever had a distant recurrence. A Cox's regression analysis with local recurrence as a time-dependent variable showed a risk ratio of 5.28 (P < 0.0001). This strong relationship is dependent on the intensity of post-treatment follow-up and investigation.