A worker is seen at a Roche production facility in a handout photo. REUTERS/Handout

ZURICH (Reuters) - A new drug from Roche Holding AG helped shrink the tumors of 25 percent of women with HER2-positive breast cancer, according to data from a mid-stage clinical trial, the Swiss company said on Thursday.

The treatment, trastuzumab-DM1, is a combination of Roche’s Herceptin and a chemotherapy agent.

About 35 percent of patients 112 in the trial either saw their tumors shrink, or their disease stabilized for at least six months, Roche said.