Assessment of Pathological Complete Response in Patients with Breast Cancer Receiving Neoadjuvant Systemic Therapy

To quantify the rate of pathological complete response (PCR) in a tertiary care hospital in Pakistan, and to explore the association of pathological complete response with tumour histology, tumour grade, and histological subtype based on receptors.

Descriptive study.

Combined Military Hospital, Rawalpindi, Pakistan from January 2016 to December 2018.

Data for 110 patients was retrospectively extracted from the medical records for the last three years. Inclusion criteria comprised of patients with non-metastatic breast cancer staged as cT1- 4 N0-1-2 breast cancer who received neoadjuvant systemic therapy, and undergone subsequent surgical procedures and adjuvant treatment as required. Assessment of pathological response was performed on the final (surgical) histopathology specimen. Complete pathological response (PCR) was evaluated according to Austrian Breast and Colorectal Cancer Study Group, and Neo-Breast International Group criteria as no invasive cancer in the breast or nodes; noninvasive breast residuals allowed (ypT0/is ypN0).

The mean age of the study group was 47.21±9.5 years with an age range of 27 - 68 years. Among 110 patients undergoing neoadjuvant systemic therapy and surgery, the rate of pathological complete response was found to be 27.2% (30/110). Univariate analysis showed that pathological complete response was significantly associated with age category, tumour grade, cancer subtype, lymphovascular invasion, and Trastuzumab administration. The occurrence of pathological complete response was significantly different among different cancer subtype groups, being highest (42.8%) among triple-negative cancer subtype, followed by HR-ve/Her+ve, HR+ve/Her+ve, and HR+ve/Her-ve (40.0%, 34.4%, and 13.0% respectively, p=0.022).

Achieving PCR after neoadjuvant chemotherapy is quite promising keeping into consideration that PCR a potential marker for progression-free survival and overall survival. Tumour grade, age of the patient, Her2 positive subtype, anti-Her2 directed therapy, and negative lymphovascular invasion are found to be potential predictors of complete pathological response.

Breast cancer, Chemotherapy, Neoadjuvant systemic therapy, Pathological complete response, Surgery.