Patients with HER2-positive advanced breast cancer and pathological complete response to neoadjuvant systemic therapy may not require surgical intervention

1. In patients with pathological complete response to neoadjuvant systemic therapy, there was no tumour recurrence at 2 years

2. No adverse events or deaths occurred secondary to vacuum-assisted core biopsy, used to determine extent of pathological response to treatment

Evidence Rating Level: 2 (Good)

Study Rundown: Prior studies have found that patients with HER2-positive breast cancer receiving neoadjuvant systemic therapy (NST) have a high rate of pathological complete response, which can be assessed using vacuum-assisted core biopsy (VACB). This study investigated radiotherapy as the sole treatment following initial standardized NST treatment with evidence of pathological complete response. The rate of recurrence of breast cancer tumour was a primary outcome of this study, while safety of VACB was a secondary outcome. A pathological complete response was identified by VACB in 31 of 50 patients and at the 2-year follow-up period, none had experienced tumour recurrence. For the VACB procedure itself, only 2 of 50 patients experienced any adverse effects; one had nausea which resolved on its own and one patient was minimally affected by equipment malfunction with no adverse event. Limitations to this study include the small sample size, and due to a potential for delayed tumour recurrence in HER-2 positive advanced breast cancers, there should be caution if considering this early data for clinical decision making. Overall, the results from this study suggest that additional trials investigating avoiding surgical intervention in HER2-positive advanced breast cancer with complete pathological response to NST will be worthwhile.

Click to read the study in The Lancet Oncology

Relevant Reading: Eliminating the breast cancer surgery paradigm after neoadjuvant systemic therapy: current evidence and future challenges

In-Depth [randomized controlled trial]: This single-arm, phase 2 trial was performed in multiple centres in the United States. This study included data from 50 female patients that were 40 years or older with confirmed HER2-positive invasive breast cancer and who had received neoadjuvant systemic therapy. The study was completed in 2 stages – a feasibility phase and an expansion cohort phase. During the feasibility stage, 6 patients were provided treatment with NST and monitored for 6 months for tumour recurrence to determine treatment plan safety. During the expansion phase, 31 of 50 (62%) patients were found to have pathological complete response (95% confidence interval (CI), 47.2 – 75.4%). Of these patients, none experienced recurrence of ipsilateral tumour after 2 years (median follow-up 26.4 months (interquartile range, 15.2 – 39.6 months)). Minimal negative events occurred during the VACB procedures, and no adverse events or deaths were reported.

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