Merck’s Top-Seller Cements Status in Hard-to-Treat Breast Cancer

Merck & Co.’s best-selling drug Keytruda helped women with a hard-to-treat form of breast cancer live longer, according to the first study to show such a benefit in these patients.

After five years, 87% of patients with early-stage triple-negative tumors who took Keytruda with chemotherapy were alive, compared with 82% of patients given chemotherapy alone. The findings, presented Sunday at the European Society for Medical Oncology Congress in Barcelona, show the initial benefits seen with treatment persist.

The data are a huge advance because there are fewer targeted drugs for triple-negative breast cancer than other types, said Rebecca Dent, ...