Locally advanced breast cancer patients with negative pathological lymph node status after neoadjuvant chemotherapy and conservative surgery: Is lymph node irradiation necessary?

e11539 Background: The increased use of neoadjuvant chemotherapy (CT) in breast cancer (BC) management has raised new questions regarding the optimal locoregional treatment. The aim of this retrospective study was to compare the outcomes of BC patients (pts) with pathological N0 status (pN0) following primary CT and conservative surgery who received breast radiotherapy with or without lymph node irradiation. Methods: Between 1990 and 2004, 1054 patients received preoperative CT for locally advanced BC. Data from 248 pts (23.5%) with clinical N0 (164 pts) or N1-N2 (84 pts) lymph node status at diagnosis and pN0 status after primary CT were studied. Among them, 93 pts (37.5%) received breast irradiation alone and 155 pts (62.5%) underwent locoregional irradiation. Outcome was assessed in relation to lymph node recurrence, disease-free survival (DFS) and overall survival (OS). Results: Both groups were comparable in terms of baseline characteristics. With a median follow-up of 88 months, 3 pts experienced nodal recurrence in the breast irradiation alone group compared with 2 pts in the locoregional irradiation group (p>.05). Among the 164 N0 pN0 pts, the 5-year DFS and OS rates were respectively 84% and 89% vs 84% and 95%, according to whether they received (n=87) or not (n=77) lymph node irradiation(p>.05). Among the 84 N1-N2 pN0 pts, same outcome values did not show any significant difference according to group of treatment: 72% and 88% in 68 pts treated with locoregional irradiation vs 81% and 81% in 16 pts treated with breast irradiation alone (p>.05). Conclusions: Our results suggest that breast irradiation alone is not associated with a higher risk of regional recurrence in locally advanced BC pts with pN0 status after neoadjuvant chemotherapy. Whether this allows the omission of lymph node irradiation for such strategy should be addressed prospectively. No significant financial relationships to disclose.