Tumor response to neoadjuvant chemotherapy in molecular breast cancer subtypes in Medellin, Colombia. Retrospective cohort study

Objectives: To describe the frequency of clinical and pathological response in different molecular subtypes of breast cancer, in patients receiving prior neoadjuvant chemotherapy.

Materials and methods: Descriptive retrospective cohort. The study population consisted of women 18 years of age and older with a histological diagnosis of invasive breast cancer stages IIA, IIB, IIIA, IIIB and IIIC, with a classification by molecular subtypes, who had received prior neoadjuvant chemotherapy, seen at a high complexity clinic in Medellin (Colombia), between July 1, 2017, and July 30, 2019. We measured age clinical stage, histological characteristics, molecular classification, and complete clinical and pathological responses by molecular subtype. A descriptive analysis was conducted.

Results: Overall, 255 patients met the inclusion criteria. Mean age was 55.2 years; the clinical stages with the highest prevalence were IIIB (28.6 %) and IIB (26.3 %), and the most frequent by histologic grading were grades 3 (48.2 %) and 2 (37.3 %). Frequency by molecular types was as follows: luminal A (10.2 %), HER2-negative luminal B (39.6 %), triple-negative (23.1%), HER2-positive luminal B (13.7 %), and pure HER2 (13.3 %). Complete clinical response following chemotherapy, by molecular type, was as follows: luminal A (26.9 %), HER2-negative luminal B (37.6 %), HER2-positive luminal B (48.6 %), pure HER2 (41.2 %), triple-negative (45.8 %). Complete pathological response by molecular subtype was achieved in the luminal A (19.2 %), HER2-negative luminal B (32.7 %), HER2-positive luminal B (54.3 %), pure HER2 (50 %) and triple-negative (42.4 %) subtypes.

Conclusions: In clinical practice, breast cancer classification by molecular subtypes is a means to approach the assess the to neoadjuvant chemotherapy. Prospective studies are needed in the region in order to determine the ability to predict overall and disease-free survival based on the complete pathologic response.