Prognostic value of biologic subtype and the 21-gene recurrence score relative to local recurrence after breast conservation treatment with radiation for early stage breast carcinoma: results from the Eastern Cooperative Oncology Group E2197 study

The present study was performed to evaluate the significance of biologic subtype and 21-gene recurrence score relative to local recurrence and local–regional recurrence after breast conservation treatment with radiation. Eastern Cooperative Oncology Group E2197 was a prospective randomized clinical trial that compared two adjuvant systemic chemotherapy regimens for patients with operable breast carcinoma with 1–3 positive lymph nodes or negative lymph nodes with tumor size >1.0 cm. The study population was a subset of 388 patients with known 21-gene recurrence score and treated with breast conservation surgery, systemic chemotherapy, and definitive radiation treatment. Median follow-up was 9.7 years (range = 3.7–11.6 years). The 10-year rates of local recurrence and local–regional recurrence were 5.4 % and 6.6 %, respectively. Neither biologic subtype nor 21-gene Recurrence Score was associated with local recurrence or local–regional recurrence on univariate or multivariate analyses (all P ≥ 0.12). The 10-year rates of local recurrence were 4.9 % for hormone receptor positive, HER2-negative tumors, 6.0 % for triple negative tumors, and 6.4 % for HER2-positive tumors (P = 0.76), and the 10-year rates of local–regional recurrence were 6.3, 6.9, and 7.2 %, respectively (P = 0.79). For hormone receptor-positive tumors, the 10-year rates of local recurrence were 3.2, 2.9, and 10.1 % for low, intermediate, and high 21-gene recurrence score, respectively (P = 0.17), and the 10-year rates of local–regional recurrence were 3.8, 5.1, and 12.0 %, respectively (P = 0.12). For hormone receptor-positive tumors, the 21-gene recurrence score evaluated as a continuous variable was significant for local–regional recurrence (hazard ratio 2.66; P = 0.03). The 10-year rates of local recurrence and local–regional recurrence were reasonably low in all subsets of patients. Neither biologic subtype nor 21-gene recurrence score should preclude breast conservation treatment with radiation.