(ChemotherapyAdvisor) – A 21-gene recurrence risk score previously validated among patients treated with endocrine therapy for ER-positive breast cancer also predicts locoregional recurrence (LRR) among patients with node-positive ER-positive breast cancer who are treated with adjuvant chemotherapy and tamoxifen, according to a study presented at the 66th Annual Society of Surgical Oncology (SSO) Cancer Symposium in National Harbor, MD.

“Recurrence score (RS) significantly predicts risk of LRR in node-positive, ER-positive breast cancer patients after adjuvant chemotherapy plus tamoxifen,” reported Eleftherios P. Mamounas, MD, Aultman Hospital, Canton, OH, and coauthors. “These findings have clinical implications regarding selection of appropriate candidates for comprehensive XRT (breast radiation).”

The coauthors analyzed data from 1,065 patients enrolled in the NSABP B-28 clinical trial. The NSABP trial compared doxorubicin/cyclophosphamide (AC × 4) versus AC × 4 followed by paclitaxel × 4 in 3,060 patients.)

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At a median follow-up of 11.2 years, 80 (7.5%) of patients had experienced LRR as first events (68% local and 32% regional), the coauthors reported.

“RS was a significant predictor of LRR” (P<0.001), the coauthors reported. “RS was significantly associated with LRR after lumpectomy plus breast XRT and after mastectomy (no XRT) as well as in patients with four or more positive nodes (with a nonsignificant trend in patients with 1-3 positive nodes).”

RS remained significantly predictive of LRR after multivariate analyses were performed to statistically adjust for treatment and surgery types (hazard ratio [HR]: 2.61; 95% CI: 1.28-5.29; P=0.008). Tumor size and pathologic nodal status also remained significantly associated with RS, the coauthors noted.

The abstract (#2) for this presentation is available at the 66th Annual SSO Cancer Symposium’s website.