Women explain why they chose double mastectomies despite having cancer in only one breast — or even in neither breast.

More women are opting to remove both breasts when cancer is found in only one.

The proportion of patients aged 45 and older who had contralateral prophylactic mastectomies rose from 3 percent in 2004 to 10 percent in 2012, according to a study published in JAMA Surgery.

Among women aged 20 to 44, it jumped from 10 percent to 33 percent.

Removing the unaffected breast does reduce the risk of cancer in that breast. However, for women at average risk, the chance of cancer developing in the other breast is small.

In addition, the surgery has not been shown to help those women live longer.

So, why do they do it?

Read more: Removing the stigma of mastectomy scars »

As genetic testing becomes more common, we know more than ever about our health risks.

BRCA1 and BRCA2 genetic mutations are associated with increased risk of breast and other cancers. Testing helps women understand the risks of developing specific types of cancer, as well as whether they can pass the mutations on to their children.

It also helps in choosing treatment options or taking preventive measures.

One of those preventive measures is prophylactic mastectomy.

For women who carry the BRCA mutations or have a strong family history of breast cancer, the surgery may reduce the risk of developing breast cancer by 90 to 95 percent.

Testing is one thing. Interpreting the results is another.

A recent survey of more than 2,000 newly diagnosed women found that half who had a double mastectomy after genetic testing didn’t actually have mutations that increase the risk of additional cancers.

They had variants of uncertain significance (VUS), which are often harmless.

About half the women who had genetic testing never spoke to a genetic counselor about the results.

Between one-quarter and one-half of breast cancer surgeons surveyed said they treat women with VUS the same way they treat women with known cancer-associated mutations.

Some women have the surgery before they ever get the results. Or before being tested at all.

Read more: New pill might make it easier to diagnose breast cancer »

At 45 years old, Charlotte Gajewski of Texas was diagnosed with stage 0 DCIS.

“It sounded simple enough,” she wrote in an email to Healthline. “But after two lumpectomies, they continued to find more positive margins with cancer cells speckled throughout my breast in a shotgun pattern.”

She tested negative for the BRCA genetic mutations and had no family history of breast cancer.

An MRI of the unaffected breast revealed a flat tumor. It was non-threatening but would need to be monitored.

“So I elected to have a mastectomy and, ultimately, a bilateral mastectomy,” said Gajewski.

Her doctor explained the pros and cons of the surgery. Her only hesitation was whether or not to spare the nipple on the unaffected breast.

She chose radical mastectomy on both so she wouldn’t have to live with doubts and fears of recurrence.

She’s happy with her decision but says she has no feeling or sensation across her entire chest, which is both annoying and a constant reminder of what she went through.

“What sounded like a simple and ‘dream’ diagnosis turned into quite a fiasco for me. But life is good now and I am healthy and joyful every day,” said Gajewski.

Mari Gallion, 47, is an author living in Alaska.

Following the diagnosis of triple-negative breast cancer, her doctor suggested breast-conserving surgery in the affected breast.

However, the first lumpectomy failed to get clear margins. The second, third, and fourth lumpectomies were also unsuccessful. It no longer made sense to keep trying to save the breast, even though she tested negative for BRCA mutations.

Together with her surgeon, she decided on a double mastectomy despite having cancer in only one breast.

The most important consideration was her health, she told Healthline.

“Early in the process, should mastectomy have become a reality, I was considering foregoing reconstruction when it was just one breast,” Gallion said. “My mom had a prosthetic, so I wasn’t afraid of that, but if two were being removed, I wanted them both done.”

Gallion feels fortunate that she was able to have the mastectomy and immediate reconstruction without the need for tissue expanders.

Not that it was easy.

She called the first four weeks after mastectomy “horrifying.”

“There were moments that I wished I hadn’t opted for reconstruction because of the pain and the time off work,” she said. “I had six surgeries all together, one of them three weeks after the mastectomy to remove the nipple, as there was a positive margin on my nipple. I understand it can be just as painful without the reconstruction. I was concerned about taking too many opioids, as I was literally watching the clock to see when I was allowed to take another pill. However, I am extremely happy with the result.”

“They [my breasts] are kind of crazy looking in that one doesn’t have a nipple, but I like that I can wear all my old clothes,” continued Gallion.

She’s considering getting a 3-D tattoo in place of the missing nipple.

Read more: Clothing that makes life easier for people with cancer »

Comedian Caitlin Brodnick has never been diagnosed with breast cancer.

But she had a double mastectomy anyway.

Some of her reasoning was based on her childhood. Her father’s entire immediate family died of various cancers, including breast cancer.

“Growing up, I was convinced I would get cancer. I was really afraid,” Brodnick told Healthline. “I was born just nine months after my aunt died of cancer. It was completely devastating and my whole family was anxious about health and cancer as a direct result.”

At 28 years old, she tested for BRCA mutations.

The result was positive.

To Brodnick, it felt like a cancer diagnosis. In fact, she refers to it as a diagnosis.

“The official diagnosis and knowing I had the genetic mutation was scary. I thought it would be easier to have something you clearly knew how to fight. The idea that you’re more likely to get cancer is very vague. You have to continually test and see doctors for screening. You’re on the defense and it’s maddening. You don’t know if cancer is lurking around the corner,” she explained.

Brodnick credits actress Angelina Jolie with jumpstarting the preventive mastectomy conversation. Jolie, who carries the BRCA1 genetic mutation, went public following her preventive double mastectomy in 2013.

“Doctors are cautious because they don’t want patients to have a mastectomy as a gut emotional response without thinking it through,” said Brodnick.

Doctors didn’t push the decision on her.

She came to it on her own after discussing it with her husband and other family members.

She’d never had a major surgery before, so there was a lot of pre-op anxiety.

“The minute I woke up after surgery I felt total relief,” she said.

She also had implants. The size didn’t work out, so the procedure had to be repeated. Other than that, there haven’t been any post-surgical complications.

“I had no idea I’d feel this great. Three years later, I’m strong and healthy.”

As satisfied as she is with her own decisions, she knows it’s not for everyone.

“A close friend had breast cancer at a young age and had a mastectomy. It was traumatic for her. Reconstructed breasts won’t ever be like real breasts,” she said.

Brodnick’s story is documented in the Screw You Cancer Series with Glamour magazine and her upcoming book, “Dangerous Boobies: Breaking Up with My Time-Bomb Breasts.”

Read more: Breast cancer treatment options by stage »

Dr. Diane M. Radford is staff breast surgical oncologist at Cleveland Clinic and medical director of the breast program at Cleveland Clinic Hillcrest Hospital.

When counseling patients with cancer in one breast, she follows the consensus statement from the American Society of Breast Surgeons and the Choosing Wisely guidelines.

“I counsel women about the lack of survival benefit with CPM (contralateral prophylactic mastectomy) and increased risk of complications such as bleeding and infection,” she wrote in an email to Healthline.

“In patients in high risk groups, such as BRCA gene carriers, the risk to the other breast is high enough to warrant CPM. My approach is evidence-based, and I review the pros and cons,” she said. “While CPM is the best risk reduction we can offer (about 95 percent risk reduction), the risk of cancer in the other breast is small in average risk women — 0.2 to 0.5 percent per year for those undergoing adjuvant therapies.”

No surgery is risk-free.

“The risk of bleeding is about 1 percent and the risk of infection is also about 1 percent,” said Radford. “So if both breasts are removed those risks rise to 2 percent and 2 percent. There is debate on whether to routinely perform sentient node biopsy for CPM. I do not routinely perform sentient node biopsy for CPM, therefore there is theoretically no risk of lymphedema with CPM.”

Medical decisions often involve more than statistics and probabilities.

There’s also a quality of life issue.

Radford explained that if, after counseling, a woman at average risk for contralateral cancer wishes CPM, she would agree to do it.

“The consensus statement states that CPM also may be appropriate for women with other conditions such as dense breasts, recall fatigue, concern about reconstruction symmetry, and extreme disease-related anxiety,” she said. “If in my opinion the patient will be extremely anxious about risk to the other breast, then for quality of life, I would perform CPM.”