A sizable subset of people with breast cancer, those who have small tumours and a favourable hormone-receptor profile but one notable risk factor — they test positive for a protein associated with more aggressive tumour growth — often are not offered chemotherapy as part of their recommended treatment strategy.

But a new analysis led by physicians at Roswell Park Comprehensive Cancer Center, published in JAMA Network Open, shows that some patients with small node-negative breast tumours that test positive for both the hormone receptor (HR) and ERBB2, also known as HER2/neu, proteins could benefit from chemotherapy in addition to surgery, radiation and endocrine therapy, also known as hormone therapy.

Led by Sung Yun Ma, MD, a resident physician at Roswell Park, the study is the first of its kind to find an association between positive outcomes and chemotherapy for breast cancers between 8 mm and 10 mm in size.

The findings, based on data on more than 10,000 patients from around the country and reported through the National Cancer Database, indicate significantly improved overall survival among those patients who received chemotherapy.

“We know that, in general, patients with this particular subset of hormone-receptor-positive breast cancers should get chemotherapy, but all the studies showing the benefits of chemotherapy included patients with large cancers,” said Anurag K. Singh, MD, Director of Radiation Research and Professor of Oncology. “The question remained whether chemotherapy was worth it for smaller tumours, given the typical side effects such as hair loss and increased nausea. So for these patients who have one risk factor, is there a benefit for the addition of chemotherapy? We found that there is a statistically significant benefit.”

The team’s retrospective epidemiologic analysis shows that risk of death within five years decreased by approximately 50% among people with small tumours of this type who received chemotherapy.

"For breast cancer, small differences become really important, and careful stratification allows us to do graduated decision-making,” noted Oluwadamilola T. Oladeru, MD, a resident physician at Massachusetts General Hospital Cancer Center who greatly contributed to this work. “Now we can say to the patient with a small tumour, ‘Here’s what happened with 10,000 other patients,’ and quantify the benefit for getting chemotherapy in their group.”

Source: Roswell Park