ANALYSIS OF TUMOR RESPONSE IN THE BREAST AND AXILLA ACCORDING TO MOLECULAR SUBTYPE IN BREAST CANCER PATIENTS SUBMITTED TO NEOADJUVANT CHEMOTHERAPY

Abstract

Objective: Pathological complete response rate (pCR), ypT0/is ypN0, after neoadjuvant chemotherapy (NAC) varies in
each molecular subtype of breast cancer, being lower in hormone receptor-positive (HR+) tumors. The objective of this
study is to analyze the pathological response rate (PR) only in the breast, only in the axilla or the pCR, correlating with
the molecular subtypes. Methods: This is a retrospective observational study of stage II and III patients undergoing NAC
between 2013 and 2020 at the Oncology and Mastology Service of Santa Casa de Misericórdia de Belo Horizonte – MG
(SCMBH). This study was approved by the Research Ethics Committee of SCMBH with the number 3,787,212 complying
with Resolution 196/96 of the National Council for Ethics in Research. Results: In all, 209 patients were selected with a
mean age of 50.6 years; 22.0% were T2, 35.9% were T3, and 42.1% were T4; 17.2% were pre-NAC cN0 and 82.7% were cN+.
Patients were divided into group A, RH+, with 147 patients (70.3%), and group B, HER2+ and TN, with 62 patients (29.7%).
When comparing PR only in the breast, RH+ patients had a better result (4.8% versus 1.6%); as well as PR only in the axilla,
37.4% against 29.0%. When subdividing group A into RH+/HER2− and RH+/HER2+, the former presented better results in
the breast (4.3% X 0%) and in the axilla (60.9% X 55.6%). Conclusion: Achieving pCR is not the only goal of NAC. Other benefits include the possibility of breast and axilla-conserving surgery. The study demonstrated good PR results in both the
breast and the axilla in group A and in the RH+/HER2− subgroup. These responses allow for a less morbid surgical treatment, both aesthetically and because of the risk of lymphedema. The data presented provide a compelling rationale for
the use of NAC in a molecular subtype considered to be relatively resistant to chemotherapy