A retrospective study measured the predictive value of the 21-gene assay recurrence score to identify breast cancer patients with a higher risk for locoregional recurrence (LRR) and therefore help guide treatment decision-making.
“The 21-gene assay recurrence score is increasingly used to personalize treatment recommendations for systemic therapy in postmenopausal women with estrogen receptor (ER)– or progesterone receptor (PR)–positive, node-positive breast cancer; however, the relevance of the 21-gene assay to radiotherapy decisions remains uncertain,” the researchers observed.
The researchers retrospectively analyzed data from the Southwest Oncology Group S8814. This phase 3 randomized clinical trial enrolled postmenopausal women with ER/PR-positive, node-positive breast cancer who received either tamoxifen alone, chemotherapy followed by tamoxifen, or concurrent tamoxifen and chemotherapy between June 1989 and July 1995. Women for whom recurrence score information data were available were included and their medical records assessed for LRR and radiotherapy use. Analyses were conducted between Jan. 22, 2016, and Aug. 9, 2019, and included 316 patients; patients were excluded if they underwent both mastectomy and radiotherapy (n = 37), received breast-conserving surgery without documented radiotherapy (n = 9), and had an unknown surgical type (n = 5). LRR was defined as recurrence in the breast; chest wall; or axillary, infraclavicular, supraclavicular, or internal mammary lymph nodes.
The mean (range) age of the 316 women included in the study was 60.4 (44.0–81.0) years; patients without LRR were followed for a median (interquartile range) 8.7 (7.0–10.2) years). LRR events occurred in 5.8% of patients with low recurrence score (n = 7/121) and 13.5% with intermediate or high recurrence score (n = 27/195). Low recurrence score patients had a 9.7% estimated 10-year cumulative incidence rate, compared to 16.5% for the intermediate or high recurrence score group (P = 0.02). This significant gap persisted among patients who had a mastectomy without radiotherapy (n = 252); the low recurrence score group had a 7.7% estimated 10-year cumulative incidence rate, compared to 16.8% for the intermediate or high recurrence score group (P = 0.03). When controlling for randomized treatment, number of positive lymph nodes, and surgical type, the researchers observed that a higher recurrence score was a significant predictor of LRR (hazard ratio, 2.36; 95% confidence interval, 1.02–5.45; P = 0.04). The researchers conducted a separate analysis of patients with a mastectomy and one to three involved lymph notes who didn’t undergo radiation therapy and observed this group was significantly less likely to sustain LRR if they had a low recurrence score versus an intermediate or high recurrence score (1.5% vs. 11.1%; P = 0.051).
The study was published in JAMA Oncology.
“This study found that higher recurrence scores were associated with increased LRR after adjustment for treatment, type of surgical procedure, and number of positive nodes. This finding suggests that the recurrence score may be used, along with accepted clinical variables, to assess the risk of LRR during radiotherapy decision-making,” concluded the researchers.