CHICAGO (AP) — New research raises fresh questions about which cancer patients benefit from Avastin, a drug that lost its approval for treating breast cancer nearly two years ago.

Avastin did not prolong life when used as a first treatment for people with brain tumors like the one U.S. Sen. Edward Kennedy died of several years ago, two studies found. In one, patients who were expected to benefit the most from Avastin based on genetic testing had the worst survival rates. Side effects also were more common with Avastin.