[en] Purpose: The results of breast-conservation therapy using breast irradiation and a boost to the tumor excision site with either electron beam or interstitial ¹⁹²Ir implant are reviewed. Methods and Materials: A total of 701 patients with histologically confirmed Stage T1 and T2 carcinoma of the breast were treated with wide local tumor excision or quadrantectomy and breast irradiation. The breast was treated with tangential fields using 4 or 6 MV photons to deliver 48 to 50 Gy in 1.8 to 2 Gy daily dose, in five weekly fractions. In 80 patients the regional lymphatics were irradiated. In 342 patients with Stage T1 and 107 with Stage T2 tumors, boost to the primary tumor excision site was delivered with 9 MeV and, more frequently, with 12 MeV electrons. In 91 patients with Stage T1 and 38 patients with Stage T2 tumors an interstitial ¹⁹²Ir implant was performed. Tumor control, disease-free survival, cosmesis, and morbidity of therapy are reviewed. Minimum follow-up is 4 years (median, 5.6 years; maximum, 24 years). Results: The overall local tumor recurrence rates were 5% in the T1 and 11% in the T2 tumor groups. There was no significant difference in the breast relapse rate in patients treated with either electron beam or interstitial ¹⁹²Ir boost. Regional lymph node recurrences were 1% in patients with T1 and 5% with T2 tumors. Distant metastases were recorded in 5% of the T1 and 23% of the T2 groups. The 10-year actuarial disease-free survival rates were 87% for patients with T1 and 75% for patients with T2 tumors. Disease-free survival was exactly the same in patients receiving either electron beam or interstitial ¹⁹²Ir boost. Cosmesis was rated as excellent/good in 84% of patients with T1 tumors treated with electron beam and 81% of patients treated with interstitial implant, and 74 and 79%, respectively, in patients with T2 tumors. Conclusions: Breast-conservation therapy is an effective treatment for patients with T1 and T2 carcinoma of the breast. There is no significant difference in local tumor control, disease-free survival, cosmesis, or morbidity in patients treated with either electron beam or interstitial ¹⁹²Ir implant boost. Clinical trials in progress will further elucidate this controversial subject