Influence de lʹirradiation locorégionale sur le contrôle local et la survie dans le cancer du sein

Summary gional control is a crucial step in the achievement of breast cancer cure. In ductal carcinoma in situ, breast irradiation significantly reduces the rates of local recurrence whatever the histological subtypes, as demonstrated by the NSABP-B17 trial (25.8% of local recurrences without radiotherapy vs. 11.4% with radiotherapy). In infiltrating breast carcinomas, complementary breast irradiation has been shown to significantly improve the local control and slightly the overall survival in five randomized trials. Following mastectomy, locoregional irradiation clearly reduces the chest wall and nodal relapse rates, especially in case of lesions more than 5 cm or with nodal involvement and/or large lymphatic or vascular emboli. Two recent randomized trials confirmed the benefit of well-adapted locoregional irradiation in all subgroups, especially in patients with one to three axillary involved nodes. In the Danish trial (including premenopausal high-risk women), radiotherapy reduced locoregional relapses from 32 to 9% (p < 0.001) and increased the 10-year survival rate from 45 to 54% (p < 0.001). In the Canadian trial, locoregional relapse rate decreased from 25 to 13% and the 10-year survival rate increased from 56 to 65%. The metaanalysis published in 1995 by the EBCTCG showed only a modest benefit due to locoregional irradiation in breast cancer. However, when small or old trials were excluded due to imperfect methodology or inadequate irradiation techniques, the benefit of modern radiotherapy became much more evident in a population of 7,840 patients. Locoregional irradiation appears to be able to reduce the risk of metastatic evolution occurring after local or nodal relapse and must be integrated in a multidisciplinary strategy. Treatment toxicity (especially toxicity due to irradiation of internal mammary nodes) is of special concern, as anthracycline-based chemotherapy is prescribed more often. The use of a direct field, with at least 60% of the dose delivered by electrons alternating with photons is recommended to protect the heart and lungs.