At ASCO, AstraZeneca reports strong data for breast cancer drug

CHICAGO — The cancer drug Enhertu stalled the growth of tumors by more than a year, significantly longer than standard chemotherapy did in women with the most common form of metastatic breast cancer — a clinical trial result that once again promises to rewrite the rules for the treatment of the disease.

The makers of Enhertu, Daiichi Sankyo and AstraZeneca, said the new data, if cleared by regulators, could shift the way physicians treat hormone receptor-positive, metastatic breast cancer, and create a new standard of care in which patients with breast tumors that express even the faintest amount of HER2 protein can benefit.

“It’s not an overestimation to say that trastuzumab deruxtecan is the most potent drug ever developed for breast cancer,” said Paolo Tarantino, a medical oncologist at the Dana-Farber Cancer Institute, using the scientific name for Enhertu. “It does come with side effects that we’re learning to manage, but with that said, I’ve never seen data like what’s being reported here.”