HER2-positive breast cancers are those in which tumors have higher levels of the HER2 protein. This form of the disease generally spreads more rapidly and has a higher rate of recurrence than HER2-negative forms. A new study finds that for those with an early stage of the disease, however, an existing treatment cuts recurrence risk.
Dr. Shahid Ahmed, an oncologist with the University of Saskatchewan’s College of Medicine, says that typically with early stage HER2-positive breast cancer, tumors larger than a centimeter or those that have spread to lymph nodes are treated with a 12-month course of monoclonal antibody trastuzumab and chemo after surgery. Dr. Ahmed led a group of researchers to see if this treatment was effective for even smaller tumors that hadn’t spread to lymph nodes. Their work, published in Nature.com Scientific Reports, shows that it is.
Dr. Ahmed explains, “Our study showed that women with HER2-positive tumors less than one centimeter and were node-negative had a low rate of recurrence. However, those who received adjuvant (post-surgical) trastuzumab had a further reduction in the risk recurrence. For example, women who did not receive adjuvant trastuzumab had a four-fold greater risk of recurrence.”
To conduct their study, the researchers looked at data from 91 Saskatchewan women who had early stage HER2-positive breast cancer tumors smaller than 10 millimeters between 2008 and 2017. Of these patients, 39 received post-surgery trastuzumab and chemo. The majority of them had tumors that were larger than five millimeters. The remaining 52 had smaller tumors and did not receive trastuzumab after their surgeries.
The team found that 97% of those who had taken the drug were recurrence-free after 10 years, while 88% of the other group were.
The study authors wrote, “Despite the low risk of recurrence in both groups, the study findings suggest that adjuvant trastuzumab further reduces the risk of recurrence, as evidenced by the lower number of recurrences in the treatment group.”
Dr. Ahmed says the results may lead to more women with tumors larger than five millimeters taking trastuzumab as part of treatment. However, the risk of treatment toxicity means it may be good to investigate if six months, rather than 12, would be more appropriate.
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