Breast cancer staging for patients with “low risk” disease: Are they all the same?
Plichta, JK; Thomas, SM; Record, S; Botty van den Bruele, A; Chiba, A; DiLalla, G; DiNome, M; Rosenberger, LH; Woriax, H; Hwang, E-SS
Published in: Journal of Clinical Oncology
6584 Background: Studies have shown that a low (<11) Oncotype DX recurrence score (RS) is associated with better survival outcomes. RS is currently included in the AJCC prognostic staging criteria. Not all patients with a low RS are downstaged. It has been suggested that a low RS should further downstage patients regardless of other disease factors. We explored survival outcomes for patients with a low RS to assess if additional patients should be downstaged. Methods: Using the National Cancer Database, female patients ages 18-75 with invasive unilateral pT1-3, pN0-1, M0 hormone receptor positive (ER+ and/or PR+), HER2- breast cancer and a RS <11, diagnosed 2010-2018 were identified. Patients who received neoadjuvant treatment were excluded. Patients were grouped based on the AJCC 8 edition prognostic stage (IA, IB, IIA, IIB, IIIA). Variables were summarized, and unadjusted overall survival (OS) was estimated using the Kaplan-Meier method. Cox proportional hazards models were used to estimate the association of stage with OS after adjustment for available covariates. Results: Of the 54,961 patients with a RS <11, median follow-up was 57.7 months (95% CI 57.3-58.1), and median age was 61yo (IQR 52-67). Most tumors were grade 1 (37.6%) or 2 (56.9%) with ductal histology (75.3%). The median tumor size was 1.5 cm (IQR 1-2), and most were pN0 (83.3%). Although most patients with a RS <11 were stage IA (94.2%), some had a higher stage assignment (5.1% stage IB, 0.6% IIA, 0.1% IIB, <0.01% IIIA). Most patients (93.4%) received endocrine therapy (ET), and few (3%) received chemotherapy. Patients treated with chemotherapy more often had younger age, lobular histology, higher grade, larger tumor size, and/or pN+ disease (all p<0.001). Unadjusted OS was reduced with higher stage (log-rank p<0.001), and this remained true when limited to only those who received ET without chemotherapy (log-rank p<0.001). After adjustment for relevant covariates including treatment, higher stage remained associated with worse OS [stage IA: ref; IB: HR 1.66 (95% CI 1.34-2.05); IIA: HR 2.29 (95% CI 1.44-3.65); IIB: HR 2.48 (95% CI 1.03-5.95); overall p<0.001]. Conclusions: For patients with a low RS, survival outcomes vary with current AJCC prognostic disease stage, suggesting that not all patients with a RS <11 should be downstaged based on RS alone. Anatomic and other non-genomic factors remain relevant when assessing prognosis. [Table: see text]
