Abstract GS5-02: Axillary dissection vs. no axillary dissection in patients with cT1-T2cN0M0 breast cancer and only micrometastases in the sentinel node(s): Ten-year results of the IBCSG 23-01 trial

Abstract

Abstract BACKGROUND: The phase III IBCSG 23-01 multicenter, randomized, non-inferiority trial compared disease-free survival (DFS) in breast cancer patients with one or more micrometastatic (≤2 mm) sentinel nodes (SNs) randomized to either axillary dissection (AD) or no axillary dissection (no-AD). Results after 5 years showed no difference in DFS between the arms. Here we report results after a median follow-up of 9.8 years. METHODS: Eligible patients had cancers of pathological diameter ≤5 cm and one or more micrometastatic (≤2 mm) foci, including isolated tumor cells, in the SNs. Patients with axillary macrometastases were excluded. Breast surgery was conservative or mastectomy. Eligible patients were randomized to AD vs. no-AD. The primary endpoint was disease-free survival (DFS); secondary endpoints were overall survival (OS), site of recurrence (particularly axillary recurrence), and surgical complications of AD. DFS and OS were estimated using the product-limit method, and the log-rank test was used to compare the treatment groups. Patients without a DFS or OS event were censored at the date of last follow-up. Non-inferiority margin for no-AD vs. AD was defined as a DFS hazard ratio (HR, no-AD relative to AD) of <1.25, and was assessed using a z-test applied to the log HR. Active follow-up of patients was terminated in February 2017. RESULTS: From 2001 to 2010, 934 patients were randomized at 27 centers; 931 were evaluable (467 in the no-AD group and 464 in the AD group). Median follow-up was 9.8 (IQR: 7.8–12.7) years. The number and types of first DFS events according to treatment group are shown in the Table. Disease-free Survival EventsNo-ADADTotal101117Breast cancer related events7475Local1413Contralateral breast1012Regional [ipsilateral axillary events]9 [8]3 [2]Distant4147Non-breast cancer related events2742Second malignancies1723Death without prior cancer event62Death with unknown cancer status417 10-year DFS was 75% (95% confidence interval [CI]: 72%–81%) in the no-AD group and 75% (95% CI: 71%–79%) in the AD group (HR [no-AD vs. AD]=0.85; 95% CI: 0.65–1.11; log-rank p=0.23; non-inferiority p=0.002). There were 45 deaths in the no-AD group and 58 in the AD group. 10-year OS was 91% (95% CI: 88%–94%) in the no-AD group and 88% (95% CI: 85%–92%) in the AD group (HR [no-AD vs. AD]=0.77; 95% CI: 0.56–1.07; log-rank p=0.19). CONCLUSION: Findings after a median follow-up of 9.8 years fully support the findings at 5 years in that no-AD is not inferior to AD with respect to DFS, and there is no significant difference between the arms for DFS and OS, thus confirming that AD is not indicated in patients with micrometastatic SNs. Citation Format: Galimberti V, Cole BF, Viale G, Veronesi P, Vicini E, Intra M, Mazzarol G, Massarut S, Zgajnar J, Taffurelli M, Littlejohn D, Egli T, Tondini C, Di Leo A, Colleoni M, Regan MM, Coates AS, Gelber RD, Goldhirsch A. Axillary dissection vs. no axillary dissection in patients with cT1-T2cN0M0 breast cancer and only micrometastases in the sentinel node(s): Ten-year results of the IBCSG 23-01 trial [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS5-02.