Pathological response of breast cancer to neoadjuvant chemotherapy at a single tertiary centre

Neoadjuvant chemotherapy (NACT) is standard treatment for eligible breast cancer patients. While guidelines recommend combining chemotherapy with trastuzumab for HER2-positive breast cancer, Groote Schuur Hospital is unable to provide trastuzumab due to cost constraints. This study examines the pathological response of breast cancer patients who received NACT, with a particular focus on HER2-positive breast cancer patients who did not receive targeted therapy, trastuzumab, in the neoadjuvant setting.

A retrospective audit was conducted on patients who received NACT followed by surgery between January 2017 and December 2018 at a tertiary hospital in Cape Town. Data on baseline tumour size, axillary staging, molecular subtype, and treatment response were analysed.

Out of 160 patients, 97.5% were female (n = 156) and 88% underwent mastectomy. Infiltrating ductal carcinoma was the most common histology (94%). Pathological complete response (pCR) was achieved by 21% of patients, and 79% had residual disease. Triple-negative breast cancer showed the best pathological response, with a 31% pCR rate (p < 0.005), while ER-positive/HER2-negative patients had a poor pCR rate of 2.4% (p < 0.005). ER-negative/HER2- positive patients had a 6.7% pCR rate (p = 0.147).

NACT is most effective for triple-negative breast cancer patients, while ER+ve/HER2-ve showed the poorest response. HER2-positive patients, all not receiving trastuzumab, showed a much lower response compared to the international norm when trastuzumab was available. Adding trastuzumab should improve pCR rates for HER2-positive patients.