ZURICH, Sept 29 (Reuters) - The U.S. Food and Drug Administration (FDA) has granted priority review for Roche's Perjeta in combination with Herceptin and chemotherapy for treating HER2-positive early breast cancer after surgery, Roche said on Friday.

The FDA is expected to make a decision on approval by Jan 28, 2018, it said in a statement.

A clinical trial for the combination therapy resulted in a modest benefit for patients, but Roche has expressed confidence that Perjeta will drive sales as it tries to offset the hit from cut-price competition to top-selling biological cancer medicines (Reporting by Michael Shields)