Although HER2-positive breast cancer is an aggressive form of the disease, recent advances in medicine have dramatically improved outcomes. Compared to a few decades ago, this type of breast cancer responds better to treatment. But people who have it still prefer mastectomies to breast-saving surgery, and researchers don’t know exactly why.

“It may be because people with HER2-positive breast cancer worry so much that mastectomy will lead to better outcomes when, in fact, mastectomy does not improve survival for most people,” says Marisa Weiss, MD, breast cancer medical director org.

“This study indicates that patients make the decision to have a mastectomy based on their disease subtype, HER2 status, which is not a reason to have a mastectomy,” Weiss says.

HER2 positive is only one phenotype or subtype of breast cancer. About 20% of all breast cancer diagnoses are HER2 positive. When caught early and treated with chemotherapy and antibody therapy, it can have a survival rate of more than 90%.

“The recommendation to undergo a mastectomy is highly dependent on the extent of the disease, rather than the phenotype,” Weiss says.

Researchers presenting data at the 2023 American Society of Clinical Oncology meeting aren’t sure why people with HER2-positive breast cancer choose mastectomy over breast-conserving surgery (BCS).

A mastectomy involves removing the entire breast. A plastic surgeon may rebuild it.

In BCS, or lumpectomy, the doctor removes the cancer while leaving the rest of the breast intact. They may also remove some lymph nodes to see if the cancer has spread. If you have a lumpectomy, you will most likely receive radiation afterwards.

Choosing lumpectomy and radiation instead of mastectomy does not affect your chances of survival. In fact, lumpectomy is associated with better survival rates than mastectomy in people with early stages of breast cancer.

The scientists looked at the types of tumors and whether people opted for a mastectomy or BCS. Of more than 543,000 people, nearly 32% had a mastectomy and about 68% had BCS between 2010 and 2019. The researchers did not look at data on people whose cancer had spread to other areas of the body. They looked at things like the size of the tumor and what stage the disease was in.

The researchers tried to select those who were candidates for a mastectomy or breast-conserving surgery. In other words, most of them should have had the freedom to choose which surgery they wanted, says Matthew Lewis Pierotti, MD, a breast surgical oncology fellow at Fox Chase Cancer Center, who led the study.

The study looked at surgery options in people with three subtypes of breast cancer: hormone receptor (HR), HER2-positive, and triple-negative (TN) tumors.

When the tumor is HR positive, that means it grows from the hormones estrogen or progesterone. Doctors treat HR-positive breast cancer with drugs that target a specific hormone.

HER2-positive breast cancer gets its name when your body makes too much human epidermal growth factor receptor 2 (HER2) protein. These tumors tend to grow faster and come back. Instead of giving hormone-based treatments, doctors should focus on HER2. In recent years, newer treatments have come on the market that have substantially improved outcomes.

Triple negative (TN) tumors are more difficult to treat because they do not have hormone receptors or HER2. They are more likely to come back and are more aggressive than HR or HER-positive breast cancers.

In the study, the researchers found that people with HER2-positive breast cancer were 1.39 times more likely to undergo a mastectomy compared to those with HR-positive cancers. But there wasn’t much difference in people who had mastectomies whether they had HR-positive or TN cancers.

People who are candidates for BCS may choose a mastectomy for a number of reasons. Some may not want to undergo radiation and others may want a more symmetrical appearance. Others may fear that the cancer may come back and think that removing the breast is the best option.

Some evidence shows that people with early-stage breast cancer may choose a mastectomy because they know they can have breast reconstruction surgery.

There are cases where a mastectomy is better, but that’s usually based on factors like the size of the tumor, how many tumors you have, and whether you’ve had breast cancer in the past.

The decision to have a mastectomy is “complex and layered,” says Mehra Golshan, MD, clinical director of the Breast Cancer Center at Smilow Cancer Hospital and Yale Cancer Center. It requires shared decision-making between patient and provider, says Golshan, who was not involved in the study.

“There are some women who absolutely have to have a mastectomy. However, most are eligible for either surgery,” says Golshan.

Todd M. Tuttle, MD, a professor of surgery at the University of Minnesota who was not part of the study team, says that being able to see differences in mastectomy rates by types of breast cancer would give more information about whether mastectomies are HER2-positive. – positive breast cancers are significantly more common.

Researchers need to look beyond the data to see why people with HER2-positive breast cancer may be more likely to choose mastectomy, says Laura S. Dominici, MD, section chief of breast surgery at Brigham and Women’s Faulkner Hospital in Massachusetts. , who reviewed the study. abstract.

They need to look at the unique characteristics of HER2-positive cancers to learn if women are less likely to be candidates for lumpectomy, Dominici says.

Golshan believes that one reason people with HER2-positive breast cancer may choose mastectomy more often than BCS is because they often have more extensive disease. But many doctors often treat the tumor with drug therapy before surgery, Golshan says.

Researchers need to examine what factors are driving the choice to have a mastectomy, Dominici says.

“This level of information cannot be obtained through … data, so more work is needed to answer that question,” Dominici says. The study raises questions that future research must answer, she says.

“More work is needed to understand why the numbers are higher with this group,” says Golshan.

Like the study authors, Dominici says mastectomy rates are declining for the most part. Double mastectomy rates began to rise in 2008, then declined around 2013, and leveled off after that. More recent data shows they dropped from 2013 to 2020 in women under the age of 40, a report says.

Another report says that BCS-eligible people choose total breast removal more often.

Mastectomy is more common in people with stage III cancer compared to other stages, newer data show.

Some people with cancer in one breast choose to have the unaffected breast removed at the same time. That procedure increased from 10% to 33% between 2004 and 2012 in women ages 20 to 44. It went from 4% to 10% among people over 45 during the same time period.

Pierotti says more people need to know about HER2-positive breast cancer tumors and how to treat them.

He plans to further study how this data compares to mastectomy trends among people who have federal health insurance through the Department of Defense, including active military, retirees and their families.

“We are trying to determine if there are specific patient or cancer characteristics that predict people will have surgery,” he says.

Pierotti agrees that they aren’t sure why people opt for a mastectomy. Options for breast reconstruction have improved, and some people may be influenced by celebrities, he says.

One study found that people who opt for mastectomy are younger, have higher levels of education and have better insurance. In some cases, they choose mastectomy because they fear the cancer will come back, the study authors say.

“We need to educate patients on the pros and cons so they can make the decision that’s right for them,” says Pierotti. “Patients have two options, and both are equivalent in terms of survival.”

The need for more aggressive systemic therapies like chemotherapy and anti-HER2 therapies doesn’t mean you need more aggressive local treatment like mastectomy, Weiss says. Lumpectomy and radiation are likely to provide the same results, she says.

“If you have HER2-positive disease, it doesn’t mean you’ll do better with a mastectomy,” Weiss says.

“Make your decision regarding your local treatment options…based on solid data, rather than your fear triggered by the aggressive nature of a particular cancer subtype,” Weiss says.