The American Society of Clinical Oncology (ASCO) published a guideline update about the selection of optimal adjuvant chemotherapy regimens and targeted therapy for early breast cancer (J Clin Oncol. 2020. doi:10.1200/JCO.20.02510).
“Patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer with pathologic invasive residual disease at surgery after standard preoperative chemotherapy and HER2-targeted therapy should be offered 14 cycles of adjuvant trastuzumab emtansine,” advised the ASCO expert panel, “unless there is disease recurrence or unmanageable toxicity.”
Published in The New England Journal of Medicine in 2019, the open-label KATHERINE phase 3 trial included patients with stage I to III HER2–positive breast cancer with residual invasive disease in the breast or axilla after neoadjuvant chemotherapy and HER2-targeted therapy. Researchers randomly assigned 743 patients to adjuvant trastuzumab emtansine, and 743 patients to trastuzumab.
Invasive disease or death occurred in 12.2% of patients who received adjuvant trastuzumab emtansine compared with 22.2% of patients who received trastuzumab, according to the panel’s review and analysis. The estimated percentage of patients free of invasive disease at 3 years was 88.3% with adjuvant trastuzumab emtansine compared with 77% with trastuzumab.
Invasive disease–free survival was significantly higher, and the risk of distant recurrence was lower, among patients who received adjuvant trastuzumab emtansine compared with trastuzumab, the study found.
In a second recommendation, the ASCO guideline addressed the use of biosimilar forms of trastuzumab—5 of which have been approved by the FDA.
“Clinicians may offer any of the available and approved formulations of trastuzumab,” the panel advised, “including trastuzumab, trastuzumab and hyaluronidase-oysk, and available biosimilars.”—Jolynn Tumolo