Suleiman Massarweh, MD, Associate Professor of Medicine at Stanford University School of Medicine, Palo Alto, and Director of Breast Clinical Trials at Stanford Cancer Institute, commented on the ADAPT trial for The ASCO Post.

“The complete pathologic response rate in estrogen receptor–positive/HER2-positive breast cancer using ado-trastuzumab emtansine (formerly T-DM1, Kadcyla) is quite impressive and suggests that more targeted therapy may be an alternative to classic chemotherapy-based regimens in this subset of HER2-positive disease,” he said. “This is important because about 50% of HER2-positive breast cancer is also estrogen receptor–positive, and these patients may not need to be treated with chemotherapy-based regimens like those with estrogen receptor–negative HER2-positive disease are.”

“The results from ADAPT are certainly encouraging and lend further support that we need to start thinking about HER2-positive breast cancer not as one disease, but as several subsets, with estrogen receptor being a clear discriminating biologic factor that can influence treatment response and the natural history of the disease,” he continued.

Although further data are needed, and ADAPT is a small study, even in neoadjuvant terms, Dr. Massarweh suggested that ado-trastuzumab emtansine can be considered for early-stage estrogen receptor–positive/HER2-positive breast cancer in situations where the patient may be frail, may have significant comorbidities, or refuses standard chemotherapy based-regimens. ■

Disclosure: Dr. Massarweh reported no potential conflicts of interest.