Abstract P1-15-09: Histological patterns of response to neoadjuvant chemotherapy in breast cancer and breast conservation

Introduction Neoadjuvant chemotherapy (NAC) in breast cancer is an in vivo marker of chemosensitivity and pathological complete response (pCR) an independent prognostic factor. When there is response, NAC downstages the tumour and may allow for or facilitate a conservative surgery. There are three histological patterns of response to NAC: a concentric pattern in which tumour regression takes place from the periphery to the center, a scatter pattern, where fibrosis is placed between tumoral cells, and a mixed pattern. Objective To determine which clinical and histological variables define the type of response to neoadjuvant chemotherapy that facilitates and allows for breast conservation in women with breast cancer. Material and methods A retrospective observational study was made including 170 patients with breast cancer who underwent NAC in the Hospital Universitari de Bellvitge between February 2010 and October 2013. Different clinicopathological parameters were recorded: age, menopausal, stage, surrogate molecular subtype, histological pattern of response, and pCR. Median age was 50 (23-78),Stage I (1.1%) IIA (27.1%) IIB (35%), IIIA (20.9%), IIIB (11.4%), IIIC (4.5%). Molecular subrogated types: Triple negative (30.7%), Luminal B Her 2 negative like (26.2%), Her 2 positive (17.7%), Luminal B Her 2 positive like (16.4%) and Luminal A like tumours (9.0%).NAC included Anthracyclines, Taxanes, and Trastuzumab if Her 2 +++. Results: Histological pattern of response: 25,5% of cases achieved a pCR. When residual tumour was observed, 42% of the cases were as scatter pattern, 21.9% as concentric pattern and 8.9% as mixed pattern. The predictive factors of pCR were in the univariate analysis: absence of multicentricity, negative estrogen receptor, negative progesterone receptor, histological grade 3, Ki 67 > 20%, and her 2 overexpression. In the multivariate analysis, only negative estrogen receptor and her 2 overexpression were predictive factors. The molecular surrogate type Her 2 positive was predictive of pCR. The predictive factors of the concentric response were in the univariate analysis: tumour size of 20% and tumour necrosis were statistically significative. The molecular surrogated type predictive of a concentric response was triple negative. Conservative surgery was more frequent in the concentric pattern group (78.4%) than in the scatter pattern (58.1%) (p=0.032) but the histological pattern of response to NAC is not correlated to survival. Conclusions Tumour size 20% and tumour necrosis were predictive of concentric pattern of response to NAC. Triple negative tumours were related to concentric histological pattern, meanwhile Her 2 overexpressed was predictive of pCR. The conservative treatment was more frequent in the concentric pattern. Histological pattern of response to NAC is not correlated to outcome. Only pCR was related to survival. Citation Format: Pla Farnos M-J, Garcia Tejedor A, Fernandez Montoli ME, Campos Delgado M, Soler Monso T, Petit Montserrar A, Morilla Ruiz I, Gil Gil M, Falo Zamora C, Ortega Martinez R, Guma Martinez A, Perez Martin X, Ponce Sebastia J. Histological patterns of response to neoadjuvant chemotherapy in breast cancer and breast conservation [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-15-09.