This study evaluates the long-term outcomes of a retrospective cohort of breast cancer (BC) patients who had received curatively intended premastectomy radiation therapy (RT). We analysed locoregional control, disease-free survival (DFS) and overall survival (OS), pathological complete remission (pCR), predictors thereof, and immediate safety. The series consisted of 187 patients with a median age of 49 years [43-60] and T2-T4 or N2 tumours. Between 1970 and 1984, they had received slightly hypofractionated RT to the whole breast, ipsilateral supraclavicular fossa and axilla ± the internal mammary chain (45-55 Gy/18 fractions of 2.5 Gy/34 days) systematically followed by a modified radical mastectomy with an axillary dissection. No other preoperative treatment was given. Among the 166 centrally reviewed tumour biopsy specimens, 22% had a triple-negative (TN) phenotype, 17% were HER2 3 + or amplified and 61% were ER+. The median follow-up was 32 years [23-35]. The 25-year locoregional control rate was 89% [93%-82%] and the 25-year DFS and OS rates were identical, 30% [24%-37%]. A pCR in the tumour and lymph nodes had been achieved in 18 among all patients (10%), but in 26% with TN disease. In the multivariate analysis, the TN status was the only predictive factor of pCR (OR = 5.49, 95% confidence interval [CI] 1.87-16.1, p = 0.002). Also, the pN status (HR = 1.69, [1.28-2.22], p = 0.0002) and TN subtype (HR = 1.80, [1.00-3.26], p = 0.05) exerted a significant prognostic impact on OS. The postoperative complication rate (grade >2) was 19% with 4.3% of localized skin necrosis. Preoperative RT followed by radical surgery is feasible and associated with good long-term locoregional control.