More and more women diagnosed with cancer in one breast are opting to remove both, even when they know the radical surgery is unlikely to prolong their lives.

In an era of concern about rising health-care costs - and decades after breast-conserving lumpectomy with radiation was shown to be effective - experts find the double-mastectomy trend puzzling and disturbing.

But it makes sense to women like Robyn Freeman of Haverford.

An ultra-fit yoga teacher, she insisted on a double mastectomy after she felt a breast lump that turned out to be early-stage cancer in March. Never mind that based on reams of research, the procedure was excessive. Never mind that she had no family history or genetic mutations that would increase her small risk of getting cancer in the healthy breast.

Her decision was shaped by the fact that at 36, with two young children, she had to fight a disease that rarely strikes before menopause.

"My husband and I were weighing the pros and cons" of double mastectomy, said Freeman, who also underwent chemotherapy. "I understand it wasn't going to change my survival. But I wanted to go through this only once. I didn't want to have those fears of getting this again. And I wasn't super tied in to my breasts."

She had another consideration, one that illustrates the emotional, sometimes contradictory nature of the thought process. Her sister-in-law, who was found to have more advanced, aggressive breast cancer seven years ago at 36, is now terminally ill - even though she, too, had both breasts removed.

Even when double mastectomy is medically unnecessary, "it might still be the right choice for some women for risk reduction, cosmetic, and/or emotional reasons," wrote Shoshana Rosenberg, an epidemiologist at the Dana-Farber Cancer Institute in Boston.

Last month, a Stanford University study of nearly 200,000 California women found the rate of double mastectomy increased from 2 percent in 1998 to 12 percent in 2011. For women under 40, the increase was even more startling - from about 4 percent to 33 percent.

After 10 years, the study found, 81 percent of double mastectomy patients were alive - about the same as for lumpectomy plus radiation (83 percent), and single mastectomy (80 percent).

Similarly, a study in the Journal of the National Cancer Institute in July found a survival benefit of less than 1 percent over 20 years for women who had double mastectomies.

Cancer specialists see this preference for aggressive surgery as a giant step backward, in defiance of advances that began in the 1980s.

Thanks to screening mammography, most of the 240,000 breast cancers now diagnosed annually are caught early. Chemotherapies and targeted therapies such as Herceptin attack microscopic metastases, which are the real threat to survival. And hormonal drugs such as tamoxifen reduce the risk of recurrence by keeping estrogen from fueling abnormal cell growth.

"There has been a movement toward less surgery, with equal outcomes and less disfigurement," said Victor G. Vogel, director of breast oncology and research at the Geisinger Health System Cancer Institute in Danville, Pa. "Unfortunately, there are still many women and some surgeons who believe more surgery cures more breast cancer."

Women who have double mastectomies generally overestimate their likelihood of getting cancer in the healthy breast. A survey led by Dana-Farber's Rosenberg found most women under 41 with no increased genetic risk believed their chance was 10 percent within five years; the actual risk is 2 percent to 4 percent.

Some women do not understand that although removing the healthy breast averts cancer there, it does nothing to ensure the initial breast tumor has not metastasized.

"Women want to feel they are doing everything they can" to fight the disease, said Jean Sachs, chief executive of Living Beyond Breast Cancer, a nonprofit education and support group in Haverford. "But there is confusion about what is a second breast cancer rather than metastatic cancer."

Even women who understand the difference may have clashing rationales, the Dana-Farber survey found: "Most women acknowledge [double mastectomy] does not improve survival; however, anxiety and fear of recurrence are likely influencing women during the decision-making process."

After conservative surgery, that anxiety can be heightened by the need to remain on guard with mammograms, MRIs, even biopsies.

In contrast, after breasts are gone, the chance of cancer in the remaining chest wall tissue is remote - less than 1 percent, studies show.

"I wanted peace of mind," Freeman said.

A minority of women, studies show, are likely to live longer if they sacrifice their breasts: Those who inherit genetic mutations that predispose them to breast cancer. And those found to have "triple-negative" cancer, an aggressive subtype that often strikes before menopause and that does not respond to targeted drug treatments.

Actress Angelina Jolie is in the former group. Last year, she revealed she had had a double preventive mastectomy to head off the disease she was 87 percent sure to develop.

Jennifer Diabo, 41, a pediatrician who lives in Elkins Park, fears she falls into both groups. She was found to have triple-negative cancer in March, after she felt a lump while breast-feeding her fourth child. Tests for known BRCA1/2 mutations were negative, but she has a worrisome family history of rare kidney and bone tumors.

"With my kooky family history, I felt it put me in a higher risk bracket," she said. "Maybe there's a genetic predisposition that hasn't been identified yet."

One consolation, she and others said, is that reconstructive surgery has come a long way, which eases the trauma of giving up organs fraught with sexual and cultural importance.

"I look pretty good. You don't see any scars," Diabo said. ""The reconstruction options are pretty incredible."