A prospective feasibility study applying the ACOSOG Z0011 criteria to Japanese patients with early breast cancer undergoing breast-conserving surgery.

BACKGROUND: In patients undergoing breast-conserving surgery and having positive sentinel lymph nodes (SLNs), the ACOSOG Z0011 trial showed equivalent loco-regional outcomes for patients receiving SLN dissection (SLND) alone and those receiving axillary lymph node dissection (ALND). We conducted a prospective single-arm study to confirm the applicability of the Z0011 criteria to Japanese patients with breast cancer. METHODS: Patients meeting the Z0011 inclusion criteria and providing consent to receive no additional ALND were prospectively enrolled at the Osaka International Cancer Institute from April 2012 to December 2016. Cumulative incidence of loco-regional recurrence was estimated and compared to that of the Z0011 study. RESULTS: Among a total of 881 patients who underwent breast-conserving surgery, 189 fulfilling the Z0011 criteria were enrolled and eligible for the subsequent analysis. Adjuvant chemotherapy was given to 113 (59.8%) patients, adjuvant hormone therapy to 170 (89.9%), and whole breast irradiation to 183 (96.8%). The frequency of tumors with positive lymphovascular invasion (p < 0.0001) and macrometastases in SLNs (p < 0.0001) were significantly higher in our study than in the Z0011 study. At the median follow-up of 36 months (range 10-64 months), only 2 of 189 patients (1.1%) experienced loco-regional recurrence. The 5-year cumulative rate of loco-regional recurrences was 1.3% (95% CI 0-3.1%), and the 3-year distant DFS rate was 96.8% (95% CI 94.0-99.6%). CONCLUSIONS: Our prospective study showed that it is feasible to apply the Z0011 strategy to Japanese patients with clinically node-negative breast cancer undergoing breast-conserving surgery with planned whole breast irradiation.