By Michelle Fay Cortez

Bloomberg News

The number of women who have both breasts removed after a one-sided cancer diagnosis has risen to more than 1 in 10, even as a new study shows the surgery doesn’t improve survival over less drastic treatment.

About 12 percent of women opted for a double mastectomy in 2011, up from 2 percent in 1998, according to a study released Tuesday by the Journal of the American Medical Association. Among those younger than 40, nearly one-third underwent the procedure.

The surgery, which gained added attention last year when actress Angelina Jolie underwent the operation, carried a survival rate of 81 percent over 10 years in about 200,000 women studied. That compares to 83 percent for patients who underwent a lumpectomy, in which only a section of a breast is removed, followed by radiation, according to the report.

“We need to make sure women are informed of all the pros and cons,” said Scarlett Gomez, a research scientist at the Cancer Prevention Institute of California and Stanford University School of Medicine.

The growth in mastectomies raises the question of “what the thought process is that women are going through, and what kind of information are they offered to enable them to make the best decision possible,” Gomez, a senior author of the report, said in a telephone interview.

The findings suggest doctors should encourage breast-conserving surgery when possible, wrote Lisa Newman, director of the Breast Care Center at the University of Michigan, in an accompanying editorial. The risk of developing cancer in the opposite breast is low, at 1 percent or less per year, she said, and most are found at early, highly curable stages of disease.

Surgery removing both breasts may be tied to a fear the cancer could return or to cosmetic reasons, since women may have better results when both breasts are reconstructed at the same time, the researchers said.

The data was taken from the California Cancer Registry and covered almost every woman diagnosed with breast cancer in the state during the study period. The database didn’t include factors such a family history or a genetic predisposition to breast cancer, which could identify women who were more likely to benefit from double mastectomy, according to Gomez.

Jolie raised the profile of the double mastectomy last year when she underwent the operation after finding out she carried a gene that gave her a 60 percent chance of developing breast cancer. Jolie hadn’t been diagnosed with cancer.

Most women getting the surgery see it as treatment for cancer in one breast and prevention of the disease in the other.

Breast cancer will be diagnosed in more than 230,000 women this year, making it the most common tumor in women, according to the American Cancer Society. It trails only lung cancer in mortality, killing 40,000 every year.

“When faced with a new breast cancer diagnosis, many patients assume that they will achieve a survival advantage by pursing the most aggressive surgical strategy,” Newman said. The California study refutes those assumptions, she said.

Still, some women may benefit from more extensive surgery and they should be informed of all their options, according to Newman. Patients should focus on learning about the different approaches in the first few weeks after diagnosis, rather than rushing into an irreversible surgery, she said.

The researchers found other factors among the women that may account for some treatment differences. Minorities, those who had no insurance or government-funded care and poorer women were more likely to have just one breast removed than white, wealthier counterparts with private insurance.

The resulting discrepancy in survival may be related to other medical conditions or challenges the women faced, Gomez said. The other challenges may have made it more difficult for the women to travel to get radiation, for example, leaving them few choices for treatment, she said.

“This should be one piece of information that comes into the discussion … when women are faced with a very difficult decision,” she said.