Assessment of clinical and pathological response to neoadjuvant chemotherapy in breast cancer according to molecular subtypes

Background. Breast cancer (BC) is the commonest tumor in women. It is the leading malignancy in world, and representing an emerging oncologic issue in all countries. In Iraq, BC cases reached 7246 in 2021by Iraqi Cancer Registry reports. Objectives. The study conducted for assessment the clinical and pathological responses to neoadjuvant chemotherapy in BC among molecular subtypes and for description the clinico-pathologic features, and patterns of BC according to molecular subtypes. Methods. A prospective study of 60 females with breast cancer histologically confirmed were enrolled. All women received neoadjuvant chemotherapy. Then all patients underwent definitive surgery including MRM+AC or BCS+AC. The patients’ demographic, the pathologic and molecular subtypes date of the primary tumor were recorded. Results. The mostly distributed age group was belong to group 46-55 yrs in 22, 36.7%. The mean age was 49.7±10.8 yrs. The IDC represented the most common histopathological types of BC. The most of cases seen in upper-outer quadrant (UOQ). The results post-chemotherapy as followed: ypTx stage reported in 32 (53.3%), ypT1 in 15 (25.0%), ypT2 in 10 (16.7%) and ypT3 in 3 (5.0%). ypN0 stage in 40 patients (66.7%), ypN1 in 11 (18.3%), ypN2 in 6 (10.0%), and ypN3 in 3 (5.0%). There was a high statistical difference between cT and ypT in pre and post-chemotherapy (P<0.0001), between cN and ypN in pre and post-chemotherapy (P=0.001) and between M and ypM in pre and post-chemotherapy (P=0.002). The mass location (P=0.005) and tumor size (P = 0.011) had significantly impacted on BC responses post NACT. 18(30.0%) had clinical complete response (cCR), 32 women (53.3%) had partial response (cPR), six cases (10.0%) had stable disease, and four cases (6.7%) had progressive disease. The cCR was better seen in T1 (77.8%) than T2 (22.2%), with statistical significant difference (P=0.002). The cCR was better seen in N0 (61.1%) than N1 (38.9%), with a high statistical significant difference (P<0.0001). Conclusions. The commonest age breast cancer is four to five decade. The IDC and mass situated at UOQ are the most common features of BC. Approximately, 30.0% of women have clinical complete response (cCR), 53.3% have partial response (cPR), 10.0% have stable disease, and 6.7% have progressive disease post NACT. The ER positive, PR positive, and HER2neu negative are the mostly frequent subtype recorded in this study. The cCR is better seen in T1 and N0 stages. ER+ and PR+ are more reported after NACT whereas HER2neu- is more post NACT.