10-yr follow-up results of NSABP B-32, a randomized phase III clinical trial to compare sentinel node resection (SNR) to conventional axillary dissection (AD) in clinically node-negative breast cancer patients.
1000 Background: NSABP B-32, the largest surgical prospective randomized phase III trial was designed to compare overall survival (OS), disease-free survival (DFS), and morbidity between SNR alone vs SNR + AD in SN negative (-) pts. We present 10 yr outcome data for primary endpoints as well as updated data on the effect of occult metastases, found later in the SN by central, detailed pathologic analysis. Methods: 5,611 women with operable, clinically N0, invasive breast cancer were randomized to SNR + AD (Group [Grp] 1) or to SNR alone with AD only if SNs were positive (Grp2). 3,989 (71.1%) of 5,611 pts were SN-. 3,986 (99.9%) of these SN- pts had follow-up information: Grp 1: 1,975, Grp 2:2,011. Median time on study was 9.4 yrs. Cox proportional hazard models adjusting for study stratification variables were used to compare OS and DFS between the two groups. Two-sided p values were used. HR values > 1 indicate a more favorable outcome in Grp 1 Results: At 10 yrs, there continues to be no significant difference in OS between the two groups (HR: 1.11, p = 0.27). 10 yr Kaplan-Meier (K-M) estimates for OS are 87.8% for SNR alone and 88.9% for SNR + AD. There continues to be no significant difference in DFS between the two groups (HR: 1.01, p=0.92). 10-yr K-M estimates for DFS were 76.9% for both groups. Occult nodal disease was originally detected in 3,884 pts (15.8%) with SN- on initial H and E analysis. Comparisons between the groups with and without occult disease yielded an adjusted HR for OS: 1.25 (p = 0.08) with an absolute difference at 10 yrs of 2.8% and a HR for DFS: 1.24 (p = 0.018) with an absolute difference of 4.1%. The cumulative incidences of local-regional events were low (10-yr values: SNR 4.0%, SNR+AD, 4.3%) and not significant (HR: 0.95, p = 0.77). Conclusions: At 10 yrs there continues to be no significant differences in OS and DFS between SNR and SNR + AD in pts with negative SN. The relative increase in risk of DFS and OS for pts with occult SN metastases remains stable. Support: PHS grants: NSABP: U10CA-12027, U10CA-37377, U10CA-69651, U10CA-69974; VT Ca Cntr: P30 CA22435; DNK: 5RO1CA074137 NCI Dpt HHS. Clinical trial information: NCT00003830.