Treatment with monoclonal antibodies after surgery reduces the risk of breast cancer coming back

Breast Cancer Concept

Treating women diagnosed with a type of early-stage breast cancer with the monoclonal antibody trastuzumab after surgery reduces the risk of the cancer coming back, reports a research team led by oncologist Dr. Shahid Ahmed (MD) from the University of Saskatchewan (USask).

The team’s study, published in the journal scientific reports, examined the medical records of all Saskatchewan women diagnosed with small HER2-positive breast cancer between January 2008 and December 2017. HER2 is one of the most aggressive types of breast cancer and is named after the human epidermal growth factor receptor 2 protein, the malfunctioning of which rapidly causes cancerous cell growth.

“HER2-positive breast cancer has been associated with a high risk of recurrence,” said Ahmed, professor and department head of oncology at USask College of Medicine.

A 12-month treatment with trastuzumab in conjunction with chemotherapy after surgery is the standard of care for HER2-positive early-stage breast cancer tumors that are larger than a centimeter or have spread to lymph nodes, Ahmed said.

However, the benefit of adjuvant (postoperative) treatment with trastuzumab for smaller HER2-positive tumors that have not spread beyond their original site (metastasized) into the lymph nodes was not known.

Shahid Ahmed

USAsk oncologist Dr. Shahid Ahmed (MD). Credit: USask

Using medical records, Ahmed’s team identified 91 women with non-metastatic, early-stage HER2-positive breast cancer smaller than 10 millimeters. A total of 39 patients, most of whose tumors were larger than 5 mm, had received adjuvant trastuzumab and chemotherapy, while 52 with smaller tumors had not received postoperative trastuzumab.

Although the sample size is small, the study is population-based with no selection bias and covers a 10-year period, Ahmed said.

“Our study showed that women with HER2-positive tumors less than one centimeter and node-negative tumors had a low recurrence rate,” Ahmed said. “However, those who received adjuvant trastuzumab had a further reduction in the risk of recurrence. For example, women who did not receive adjuvant trastuzumab had a four-fold increased risk of recurrence.”

Overall, 97 percent of the women in the trastuzumab group were free of breast cancer recurrence at 10 years, compared with 88 percent of the women who did not receive the treatment.

The analysis of this retrospective cohort study was statistically adjusted to account for factors such as patient age and other risks to bring the results as close as possible to those of a randomized trial, Ahmed said.

He believes that study results, which favor the adjuvant use of trastuzumab in small tumors, will lead to more widespread use to reduce the risk of cancer recurrence in younger women with tumors larger than 5 mm.

However, since treatment toxicity is an important consideration when considering the use of adjuvant trastuzumab, a key issue to consider is whether the treatment duration should be reduced to six months from the current 12 months, he said.

Reference: “Efficacy of adjuvant trastuzumab in women with HER2-positive T1a or bN0M0 breast cancer: a population-based cohort study” by Sanji Ali, Jace Hendry, Duc Le, Prosanta K. Mondal, Amer Sami, Haji Chalchal, Kamal Haider, Osama Ahmed , Ali El-Gayed, Philip Wright, Mehrnoosh Pauls, Kate Johnson and Shahid Ahmed, January 20, 2022, Scientific Reports.
DOI: 10.1038/s41598-022-05209-8 Treatment with monoclonal antibodies after surgery reduces the risk of breast cancer coming back

Tom Vazquez

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