No benefit to adding adjuvant chemo to hormonotherapy in high-risk breast cancer

Adding adjuvant chemotherapy to hormonotherapy does not appear to improve survival outcomes in older women with high-risk estrogen receptor (ER)-positive, HER2-negative breast cancer and is even associated with more adverse events, as shown in a phase III study.

The study included 1,089 patients aged ≥70 years (median age 75.1 years) with a high-risk ER-positive HER2-negative invasive breast cancer, according to genomic grade index (GGI). GGI testing was performed with a reverse-transcriptase PCR assay of eight genes on paraffin-embedded tumour tissue in a central laboratory. A total of 437 patients (40 percent) had geriatric frailty (G8 score ≤14) at baseline.

The participants were randomly assigned to receive either four cycles of postoperative taxane-based or anthracycline-based chemotherapy, administered every 3 weeks, followed by hormonotherapy (chemotherapy group, n=541) or hormonotherapy alone (no chemotherapy group, n=548).

Over a median follow-up of 7.8 years, overall survival rates did not significantly differ between the chemotherapy and no-chemotherapy groups across several time points: 90.5 percent vs 89.3 percent at 4 years (absolute difference, 1.3 percentage points, 95 percent confidence interval [CI], –2.4 to 5.0) and 72.7 percent vs 68.3 percent at 8 years (absolute difference, 4.5 percentage points, 95 percent CI, –2.1 to 11.1).

Safety data looked better in the no-chemotherapy vs chemotherapy group. At least one grade ≥3 adverse event occurred in 34 percent of patients in the chemotherapy group as opposed to only 9 percent in the no-chemotherapy group. Three deaths were recorded in the chemotherapy group, one of which was related to treatment, whereas one death unrelated to treatment was documented in the no-chemotherapy group.

The findings provide evidence on the benefit–risk balance of adding adjuvant chemotherapy to adjuvant hormonotherapy in this older age group of patients with high-risk tumours.