Decision-making impact on adjuvant chemotherapy allocation in early node-negative breast cancer with a 21-gene assay: systematic review and meta-analysis.

Risk stratification based on results provided by a 21-gene assay (Oncotype DX(®)) in early stage breast cancer can help optimize hormone therapy (HT) and/or chemotherapy (CT) decisions. We performed a systematic review and meta-analysis of decision impact (DI) and net change in CT use before and after assay results, both in the whole studies' population and by recurrence risk score (RS) strata. A systematic search of studies with prospective data collection reported physician's decision on treatment allocation in early stage node-negative breast cancer was performed. DI reflects the proportion of patients whose management was changed, and net change focuses on CT change. A random-effects model is reported. Fifteen studies (N = 2229) met our inclusion criteria: 50.09, 37.35, and 13.38 % of patients with low, intermediate, and high RS. Treatment decision changed in 29.5 % (95 % CI 26.29-32.86). Net reduction of CT use was 12 % (8-17 %). It was 16 % (12.00-19.00) in the low RS group, 0 % (-3.00 to 3.00) in the intermediate RS group, and increased by 2 % (-1.00 to 3.00) in the high RS group. Use of a 21-gene assay showed a significant impact on treatment decisions. From 100 women tested, 30 could have their treatment optimized, and 12 could avoid CT. Its main effects consist of sparing chemotherapy in low risk patients and slightly increasing it in the high risk category. DI could be higher in selected patient populations with greater uncertainty regarding initial treatment decisions.