WASHINGTON (AP) — U.S. regulators are convening a meeting to consider clawing back approvals from several cancer drugs that have failed to show they extend or improve life. Each year the U.S. approves dozens of new uses for cancer drugs based on early signs that they can shrink or slow tumor growth. But sometimes those promising results don’t translate into longer life for cancer patients. On Tuesday, the FDA starts a three-day meeting on the issue. It’s the first such meeting in a decade. The agency has only once used its power to revoke a cancer drug’s early approval.