The 21-gene assay recurrence score can aid decisions about radiotherapy for postmenopausal patients with node-positive breast cancer, according to researchers.
The researchers analyzed patients who underwent mastectomy or breast-conserving surgery (excision and radiation) and received chemotherapy plus tamoxifen or tamoxifen alone. Results showed that patients with an intermediate or high recurrence score, according to the 21-gene assay OncotypeDX, were more likely to have locoregional recurrence (LRR).
“We believe that the recurrence score adds independent prognostic information that could be used with standard clinical factors for identifying LRR risk and making radiotherapy decisions,”of the University of Texas MD Anderson Cancer Center, Houston, and coauthors wrote in .
Dr. Woodward and colleagues analyzed data from a phase 3 trial () of postmenopausal women with estrogen or progesterone receptor–positive, node-positive breast cancer. There were 367 patients who received tamoxifen alone (n = 148) or cyclophosphamide, doxorubicin, and fluorouracil followed by tamoxifen (n = 219).
Of the 367 patients, 316 were included in the primary analysis. This includes 252 patients who underwent mastectomy without radiotherapy and 64 patients who underwent breast-conserving surgery with radiotherapy.
The researchers defined LRR as a recurrence in the breast; chest wall; or axillary, infraclavicular, supraclavicular, or internal mammary lymph nodes.
The LRR incidence was 5.8% (7/121) among patients with a low recurrence score and 13.8% (27/195) among patients with an intermediate or high recurrence score. The estimated 10-year cumulative LRR incidence rates were 9.7% and 16.5%, respectively (P = .02).
The researchers conducted a multivariable analysis for LRR, which included the recurrence score, randomized treatment (combination regimen vs. tamoxifen alone), number of positive nodes (three or fewer vs. four or more), and type of surgery (mastectomy vs. excision and radiation).
Having intermediate or high recurrence scores was a significant predictor of LRR, with a hazard ratio of 2.36 (P = .04). Having four or more involved nodes was a significant predictor of LRR as well (hazard ratio, 3.37; P = .001). Randomized treatment and surgery were not significantly associated with LRR.
The researchers also conducted an exploratory analysis and found that a recurrence score of 18 was the optimal cutoff for the association of recurrence score and LRR.
“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,” Dr. Woodward and colleagues wrote. “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. We recommend considering the recurrence score, when available, as one of the factors in selecting patients for postmastectomy radiotherapy.”
This research was funded by the National Cancer Institute of Canada, Canadian Cancer Society, and Genomic Health, which markets the 21-gene assay OncotypeDX. Dr. Woodward disclosed receiving personal fees from Genomic Health outside this research as well as an advisory fee from Merck.
SOURCE: Woodward WA et al. JAMA Oncol. 2020 Jan 9.