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Top Line: Does post-mastectomy radiation (PMRT) carry the same benefit in the setting of trastuzumab for HER2(+) breast cancer?
The Study: PMRT has a well established role in the treatment of node-positive breast cancer. More recently, the landmark HERA trial established the role of adjuvant trastuzumab for women with HER2(+) breast cancer. There were over 5000 women enrolled, 1600 of whom had mastectomy and adjuvant trastuzumab with (58%) or without (42%) PMRT. Importantly, PMRT was at physician discretion. That means the people who received PMRT had more aggressive clinical features: young age, extensive nodal disease, large tumor size, and negative hormone-receptor status. To put this in perspective, 63% of all the patients who received PMRT had four or more nodes involved, while 56% of the patients who didn’t get PMRT had zero nodes involved. With that built-in selection bias in mind, this unplanned secondary analysis demonstrates patients who received PMRT still had significantly improved disease-free survival from 70 → 77% at 10 years. Granted, among only node-negative patients, no benefit was seen with PMRT. But, for those with N1 disease, 10 year local recurrence-free survival was improved from 90 → 97% and there was even a “trend” towards improved overall survival. When looking at receptor status, it was triple-positive patients who seemed to benefit most. While not directly explored here, this is in line with data suggesting disease that benefits less from chemo (i.e. hormone-receptor positive) benefits more from locoregional radiation.
TBL: Despite highly effective targeted therapy, patients with HER2(+) node-positive breast cancer still derive a significant benefit from PMRT. | Jaoude, Int J Radiat Oncol Biol Phys 2019