CHICAGO (AP) — A big study says removing both breasts to treat cancer in just one doesn’t boost survival for most women. That’s compared with removing just the tumor plus radiation.

The results raise concerns about a riskier, potentially unnecessary operation that increasing numbers of women are choosing.

The study involved nearly 200,000 California patients followed for several years.

Ten-year survival rates were nearly identical — or roughly 82 percent — for lumpectomies plus radiation, and for double mastectomies. Women who had a single mastectomy, removal of just the cancerous breast, fared slightly worse.

Most women choose lumpectomy treatment. But double mastectomies have increased substantially in recent years, especially in younger women.

The study was published Tuesday in this week’s Journal of the American Medical Association.