LAUSR

Introduction There is extensive evidence associating the response to neoadjuvant chemotherapy (NeoCT) with breast cancer (BC) survival. However, to the author’s knowledge, there is no published data in Chile. The objective of the study is to evaluate whether achieving pathological complete response (pCR) after NeoCT is associated with greater survival and lower risk of recurrence in a Chilean Public Health Service. Methods Retrospective analysis of a database. Patients with a diagnosis of Stages I–III BC who received NeoCT between 2009 and 2019 were included. Clinical and pathological information were extracted from the clinical records. BC subtypes were defined using hormone receptor (HR) information (HR: oestrogen and/or progesterone) and epidermal growth factor type 2 (HER2), being divided into four groups: HR+/HER2−, HR+/HER2+, HR−/HER2+, HR-/HER2−. pCR was defined as the absence of invasive cancer in the breast and axilla (ypT0/is N0) after NeoCT. Results Of 3,092 patients, 17.2% received NeoCT. Of these, 40.2% corresponded to HR+/HER2−, 20.9% HR+/HER2+, 18.2% HR−/HER2+ and 20.7% HR−/HER2−. Overall, 24.8% achieved pCR, being the lowest for HR+/HER2− (10.3%) and the highest for HR−/HER2+ (53.2%). In the multivariable analysis, family history, HER2+ and type of chemotherapy were associated with a greater probability of pCR. With a median follow-up of 40 months, the overall survival and metastasis-free survival (MFS) at 3 years were greater for the group with pCR compared to that which did not achieve it (90.5% versus 76.7%, p = 0.03 and 88.5% versus 71.4%, p = 0.003, respectively). The multivariable analysis confirmed this finding. Brain MFS was similar in both groups. Conclusion NeoCT is associated with greater pCR in aggressive BC subtypes. In those, achieving pCR was associated with better survival in our study. To the author’s knowledge, this is the first study which evaluates the relation between pCR and BC subtypes in a Chilean public hospital.