[Role of lymph node irradiation in breast cancer patients with negative pathologic node status after neoadjuvant chemotherapy: the René-Huguenin Cancer Center experience]. / Rôle de l'irradiation ganglionnaire chez les patientes indemnes d'envahissement ganglionnaire après chimiothérapie néoadjuvante pour un cancer du sein: expérience du centre René-Huguenin.

ABSTRACT

PURPOSE: Neoadjuvant chemotherapy generally induces significant changes in the pathological extent of disease. This potential down-staging challenges the standard indications of adjuvant radiation therapy. We assessed the utility of lymph node irradiation in breast cancer patients with pathological N0 status (pN0) after neoadjuvant chemotherapy and breast-conserving surgery. PATIENTS AND MATERIALS Among 1054 breast cancer patients treated with neoadjuvant chemotherapy in our institution between 1990 and 2004, 248 patients with clinical N0 or N1-N2 lymph node status at diagnosis had pN0 status after neoadjuvant chemotherapy and breast-conserving surgery. Cox regression analysis was used to identify factors influencing locoregional recurrence-free survival, disease-free survival and overall survival. RESULTS: All 248 patients received breast irradiation, and 158 patients (63.7%) also received lymph node irradiation. With a median follow-up of 88 months, the 5-year locoregional recurrence-free survival and overall survival rates were respectively 89.4% and 88.7% with lymph node irradiation and 86.2% and 92% without lymph node irradiation (no significant difference). Survival was poorer among patients who did not have a pathological complete primary tumor response (pCR) (hazards ratio [HR]=3.05; 95% CI, 1.17 to 7.99) and in patients with N1-N2 clinical status at diagnosis ([HR]=2.24; 95% CI, 1.15 to 4.36). Lymph node irradiation did not significantly affect survival. CONCLUSIONS: Relative to combined breast and local lymph node irradiation, isolated breast irradiation does not appear to be associated with a higher risk of locoregional relapse or death among breast cancer patients with pN0 status after neoadjuvant chemotherapy. These results need to be confirmed in a prospective study.