Despite continually improving outcomes for women diagnosed with early stage breast cancer, there is an unmet need to identify those with elevated risk after standard treatment for whom enhanced treatment strategies should be considered. A poor response-type (RSt) signature has been assessed in women treated with breast conserving surgery. This study includes patients from two separate hospitals in Sweden diagnosed with early stage breast cancer (tumor size 20 mm or less) and treated with breast conserving therapy between 1987 and 2004. Women with positive margins, lymph node metastases, or those treated with mastectomy or chemotherapy were excluded. The RSt biosignature was calculated using biomarkers (ER, p16/INK4A, Ki-67, COX-2, PgR, HER2, FOXA1, SIAH2) scored by board certified pathologists in a CLIA certified laboratory. Pathology and clinical data were collected from medical records. There were 284 eligible patients with biomarker data and 102 received hormone therapy. Multivariate Cox proportional hazards and survival analysis were used to assess cumulative incidence risk differences, hazard ratios, and 10-year risks. Women with a poor RSt remained at particularly elevated risk after treatment with breast conserving surgery and radiation therapy with a 17% 10-yr risk and HR = 3.7 (95%CI 2.0-7.10), p<0.00001 (Table 1). The distribution of size and grade were similar for good versus poor RSt. Patients with a poor RSt had an elevated risk of disease-specific death; HR = 2.9 (95%CI 1.3-6.7), p = 0.01. A novel biosignature identified women diagnosed with early stage invasive breast cancer with a low risk and a poor RSt. Women with a poor RSt remained at particularly elevated risk even after RT, and thus enhanced treatment strategies should be considered for these women.Abstract 2041; TableRSt GroupPatientsEvents10-Year Event Risk (95% CI)Local Regional Events10-Year Specific Death (95% CI)Breast Cancer DeathsLow Risk16574% (1-8)52% (0-5)2Poor RSt681117% (7-25)513% (5-21)9 Open table in a new tab
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