CONTRALATERAL PROPHYLACTIC MASTECTOMY DISCOURAGED

Women diagnosed with breast cancer who are at average risk should be discouraged from undergoing a contralateral prophylactic mastecotomy (CPM), because the majority of women will obtain no oncologic benefit, says a new consensus statement from the American Society of Breast Surgeons (ASBrS).

The ASBrS notes that it is endorsing a previous statement issued by the American Board of Internal Medicine's Choosing Wisely campaign that women with cancer in a single breast should not undergo prophylactic mastectomy unless the woman is well informed about the risks associated with CPM and makes her decision on the basis of facts and not fear.

The ASBrS consensus statement consists of two parts. The firstoutlines the effect that CPM has on relevant clinical outcomes and which patients might be appropriate candidates for CPM. The second concerns issues such as how patients feel about CPM. Both position statements were published online July 28 in the Annals of Surgical Oncology.

"Having spoken with many of these women, they often want to take control of as many aspects of this process as they can, and as a society, we just want to make sure that women realize that CPM is not going to improve their survival, that their risk of developing cancer in the other breast is much lower than they presume it is and then try to reassure them that they will most likely be followed closely and that if anything is detected in the other breast, it will be detected early," Judy C. Boughey, MD, professor of surgery, Mayo Clinic, Rochester, Minnesota, who is the lead author of the ASBrS position paper, told Medscape Medical News.

"The really critical thing to ask is, 'Why does the patient think she wants to remove the other breast?' And if they say, 'I want to do this to treat my cancer,' then you need to redirect and reeducate," she added.

From the main ASBrS position paper, the bottom-line recommendations are as follows:

• Average-risk women with unilateral breast cancer should be discouraged against undergoing CPM.
• CPM should also be discouraged in women with an advanced index cancer, in women at high risk for surgical complications, and in women who test negative for BRCA despite having a family member who is positive for BRCA.
• Men with breast cancer, regardless of their BRCA status, should similarly be discouraged from having the contralateral breast removed.

Rational for ASBrS Recommendations

First and foremost, the ASBrS consensus panel advocates that a breast-conserving approach be used for appropriate candidates and that consideration be given to the use of neoadjuvant therapy or other approaches to make it more likely that a patient receives breast-conserving surgery whenever possible

"Breast conservation is equivalent to mastectomy in survival outcome and has been the preferred treatment for early-stage breast cancer since the National Cancer Institute statement in 1991," Dr Boughey and colleagues observe

"And increase in the use of breast conservation can decrease CPM rates," they add.

However, the issue of CPM often arises when women must undergo or choose to undergo mastectomy for treatment of their breast cancer.

In such cases, justification for undergoing prophylactic mastectomy depends on a woman's risk of developing contralateral breast cancer (CBC).

Dr Boughey and colleagues point out that historically, the absolute risk for women developing a CBC was approximately 0.6% a year, but adjuvant chemotherapy, tamoxifen, and aromatase inhibitors have reduced this risk from 0.2% to 0.5% a year.

On the other hand, for known carriers of the BRCA1/2 mutation, the risk of developing a CBC is as high as 40% at 10 years, and the risk appears to increse with time.

Women who are diagnosed with breast cancer at a young age, as well as those with a strong family history of breast cancer, are also at higher risk for CBC, consensus panel members point out.

However, as panel members note in their position paper, no prospective studies have evaluated CPM on relevant cancer endpoints, so its effect on survival is unknown.

Having reviewed what evidence there is, the panel members concluded that CPM does not seem to improve survival, with the possible exception of BRCA carriers, for whom CPM may be beneficial.

Importantly, too, CPM is not 100% protective against the development of CBC, a fact that undermines its purpose, they add.

Surgical Risks With CPM

Women who are considering CPM should also be made aware that the procedure carries a not insignificant risk for adverse outcomes, including permanent numbness of the chest.

"CPM has been shown to double the complication rate compared to unilateral mastectomy, regardless of whether reconstruction is performed or not, and complications occur almost equally on the affected and prophylactic sides," Dr Boughey and colleagues note.

CPM can also adversely affect cancer outcomes for patients who were never destined to develop a CBC, she adds, and patients who undergo reconstructive surgery for both breasts have reported that cosmetic outcomes, numbness, and tingling were worse than they expected.

It has been Dr Boughey's personal experience that desire for symmetry in their reconstructed breasts is a key driver behind a woman's opting for CPM.

"Especially if women are having reconstruction, they often want to have a reconstructed pair," she explained