Rate of clinical progression of neoadjuvant therapy (NAT) in triple-negative breast cancer: An updated analysis of response to NAT in locally advanced breast cancer (LABC) by tumor subtype.

Abstract

e11035 Background: Neoadjuvant chemotherapy is considered standard of care in the treatment of LABC. It is recognized that subtypes of breast cancer may have differential benefit from the use of chemotherapy. The aim of this study was to determine clinical and pathologic response rates to NAT in these different subtypes. Methods: Patients with LABC (stage 2B/3) treated with NAT who were entered into the prospective database at the Sunnybrook Odette Cancer Center were included in the analysis. Patients were classified using immunohistochemical profiles as 1. Luminal A (ER+ and/or PR+, HER2-); 2. Luminal B (ER+ and/or PR+, HER2+; 3.HER2+ [HER2+ ER- PR-]); and 4. triple-negative (TN) (ER-, PR-, HER2-). Clinical and pathologic response to NAT was assessed and compared across the four subtypes. Pathologic complete response (pCR) was defined as no residual invasive disease in the breast or axilla. Results: Between Jan 2003 and Dec 2007, 143 patients received NAT and were included in the analysis. 69 (48%) were luminal A, 18 (13%) luminal B, 24 (17%) HER2-positive, and 32 (22%) were TN. All patients received an anthracycline and 63% received anthracycline and taxane. Median age at diagnosis was 57 and was not statistically different across subgroups. Clinical response rates were luminal A (81%) luminal B (83%), HER2+ (78%) and TN (48%). Patients in the TN group were more likely to progress while on NAT (25%) compared to other subgroups (3.4%) (p < 0.0001).25% of these patients were made operable by salvage radiation therapy. pCR rate for all patients was 10% but was not statistically different across subgroups (luminal A 5%, luminal B 19%, HER2+ 13% and TN 16%) (p = 0.312). Conclusions: Clinical and pathological response rates differ significantly between different tumor subtypes. The low pCR rate amongst the subgroups reflects the advanced stage of these patients. Clinicians treating patients with TN LABC need to watch patients closely given the high rate of clinical progression. Innovative strategies need to be developed if we are to continue to use CCR and pCR as surrogates for long-term benefits from systemic therapy. No significant financial relationships to disclose.