摘要：Abstract Background Whether radiotherapy (RT) is beneficial in elderly (⩾70 years) patients undergoing conservative surgery for early breast cancer has long been controversial. Recent randomised trials show that most elderly patients do not benefit from RT. We started a prospective non-randomised trial to address this issue in 1987 and now present results for the 627 consecutive pT1/2cN0 patients recruited, and treated by conservative surgery (quadrantectomy) and tamoxifen, and assigned non-randomly to RT or no RT. Methods We used multivariate competing risks models to estimate 15-crude cumulative incidence (CCI) of ipsilateral breast tumour recurrence (IBTR), distant metastasis and breast cancer mortality. The models incorporated a propensity score as a measure of probability of receiving RT based on baseline characteristics, to account for the lack of randomisation. Results For pT1 patients, 15-year CCIs of IBTR, distant metastasis and breast cancer death were indistinguishable in the RT and no RT groups. For pT2 patients, 15-year CCI of IBTR was much higher in those not given RT (14.6% versus 0.8%, p = 0.004), although breast cancer mortality and distant metastasis did not differ significantly between RT and no RT. Conclusions Consistent with the findings of recent randomised trials, our long-term data indicate that most elderly, ER-positive patients with pT1 cN0 breast cancer treated by quadrantectomy do not benefit from RT. The 14.6% CCI of IBTR in our pT2 patients is an additional finding not presented in the trials and suggests that RT should be administered to elderly patients with pT2 disease.