Treating women diagnosed with a certain type of early-stage breast cancer with the monoclonal antibody trastuzumab after surgery may reduce the risk of the cancer returning, according to a report published by Ali et al in Scientific Reports.
The research team from the University of Saskatchewan examined the medical records of all Saskatchewan women diagnosed with a small HER2-positive breast cancer between January 2008 and December 2017.
“HER2-positive breast cancer has been associated with high risk of recurrence,” said senior study author Shahid Ahmed, PhD, MD, FRCPC, FACP, Professor and Division Head of Oncology at the University of Saskatchewan’s College of Medicine.
Shahid Ahmed, PhD, MD, FRCPC, FACP
A 12-month course of treatment with trastuzumab in conjunction with chemotherapy after surgery is the standard treatment for early-stage HER2-positive breast cancer tumors that are larger than 1 cm or that have spread to lymph nodes, Dr. Ahmed said. However, the benefit of adjuvant trastuzumab for smaller HER2-positive tumors that haven’t spread beyond the initial site to the lymph nodes was not well known.
Study Findings
Using the health records, Dr. Ahmed’s team identified 91 women who had early-stage, localized HER2-positive breast cancers smaller than 10 mm. Overall, 39 patients whose tumors mostly were larger than 5 mm had received adjuvant trastuzumab and chemotherapy, while 52 with smaller tumors had not received postoperative trastuzumab.
While the sample size is small, the study is population-based with no selection bias and covers a 10-year period, Dr. Ahmed said.
“Our study showed that women with HER2-positive tumors less than 1 cm and who were node-negative had a low rate of recurrence,” Dr. Ahmed said. “However, those who received adjuvant 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.”
Overall, 97% of women in the trastuzumab group were free of a breast cancer recurrence after 10 years, compared to 88% among those who didn’t receive the treatment.
The analysis of this retrospective cohort study was statistically adjusted to account for such factors as patient age and other risks, to make the findings as close as possible to those of a randomized study, Dr. Ahmed said.
He anticipates the findings of the study, which favor adjuvant trastuzumab for small tumors, will lead to its more frequent 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 in contemplating the use of adjuvant trastuzumab, a key point to examine is whether the duration of treatment should be shortened to 6 months from the current 12 months, he said.
The study authors concluded, “Women with HER2-positive T1a/bN0 breast cancer had overall low recurrence of breast cancer. However, the results of this exploratory analysis indicate that women who received adjuvant trastuzumab had better survival.”
Disclosure: For full disclosures of the study authors, visit nature.com.
