Abstract 1880: Pathologic response pattern of breast cancer after neoadjuvant chemotherapy: its correlation with molecular subtypes

Abstract

Abstract Background: Several ways to assess pathologic response of breast cancer after neoadjuvant chemotherapy (NAC) are currently used, including Miller-Payne system and residual cancer burden. However, the relationship between pathologic response pattern and molecular subtype of breast cancer is unclear. Methods: We investigated the pathologic response pattern of breast cancer after NAC in each molecular subtype. Female breast cancer patients who received NAC and subsequent breast operation were retrospectively analyzed. The NAC regimen used for breast cancer was primarily anthracycline and taxane-based, depending on the axillary lymph node involvement. We evaluated the molecular subtypes by immunohistochemistry, pretreatment tumor sizes by MRI, absolute invasive tumor cellularities in pretreatment biopsy and operation specimens, pathologic complete response (pCR) rates, posttreatment pathologic tumor sizes, overall residual tumor cellularities, and grades for Miller-Payne system. Results: A total of 119 patients (age: 45.2 ± 9.5 yr) were enrolled. Sixty-six cases were hormone receptor positive (ER or PR positive), 18 cases were HER2 positive (ER and PR negative), and 35 cases were triple negative. There were no significant differences in pretreatment tumor size by MRI and absolute cellularity in biopsy between three groups. After NAC, hormone receptor positive tumors showed the lowest pCR rate (18.2 %) while triple negative tumors showed the highest pCR rate (45.7 %, p=0.013). In patients with residual carcinoma, hormone receptor positive tumors showed the largest ypT size (p=0.016), the least reduction of tumor size (p=0.001), and the least absolute invasive tumor cellularity (p=0.006). Overall residual tumor cellularity and Miller-Payne grade were not significantly different between three groups (p=0.4 and p=0.703, respectively). Conclusion: These results suggest that each molecular subtype of breast cancer shows characteristic pathologic response patterns following NAC. Citation Format: In-Hye Song, Hee Jin Lee, Gyungyub Gong. Pathologic response pattern of breast cancer after neoadjuvant chemotherapy: its correlation with molecular subtypes. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1880. doi:10.1158/1538-7445.AM2014-1880