New study: Double mastectomy doesn't improve breast cancer survival

When you think of breast cancer, it might be easy to conjure an image of mastectomies and baldness. However, times have changed, treatments have advanced, and breast cancer doesn’t automatically mean mastectomy.

When faced with a breast cancer diagnosis, women and their families are faced with decisions about surgery and treatment. In some cases, women with cancer in one breast, opt to have a double mastectomy to prevent cancer coming back in the second breast.

However, new research has found patients who opt for a double mastectomy don't see an improvement in overall survival, when compared to single mastectomy or breast conserving surgery (lumpectomy or partial mastectomy). This raises questions about the need for a long operation - which carries its own risk - if there is no benefit to survival.

The study, published JAMA Oncology, looked at data from more than 660,000 women of various ethnicities in a large U.S. cancer registry. The average age of each woman was 58, and all had been diagnosed with breast cancer in one breast.

Women were matched in terms of the features of their breast cancers including stage and grade of each tumour. Each patient had one of three surgeries,

• Lumpectomy – to remove only the tumour in the affected breast.
• Single (or unilateral) mastectomy, removing the breast containing the tumour, or
• Double (bilateral) mastectomy, removing both breasts.

Following surgery, researchers tracked whether the women developed breast cancer in their remaining breast over a period of 20 years. When this happens, it is called contralateral breast cancer. Despite the removal of a second breast in people with a double mastectomy, there is still a chance of developing contralateral breast cancer because some leftover breast tissue or cancer cells may recur on the chest wall. The risk of a diagnosis of breast cancer in the second breast is about 0.4% per year following initial diagnosis.

Researchers also tracked deaths from breast cancer over this 20-year period. They found that overall, women who'd had a double mastectomy did have a lower risk of developing contralateral breast cancer than the other groups (0.7% versus 6.9%). However, there was no difference in overall death rates between groups. In the lumpectomy group 16.3% died over the 20-year period compared to 16.7% for both types of mastectomies.

It seems counterintuitive. If cancer is less likely to return in a second breast following bilateral mastectomy, why are death rates between the three types of surgery the same?

A possible reason for this is that the original breast cancer is the main driver of deaths in these patients, rather than the breast cancer in the second breast according to Dr Seema Khan, a cancer researcher from Northwestern University in Illinois.

Dr Khan wrote an accompanying editorial to the study and said there may be significant time gaps between the original tumour diagnosis and a second cancer developing. Patients could well be treated with “older, less effective regimens and the risk of death from contralateral breast cancer may be lower than the original tumour.” Dr Khan also noted second cancers may be diagnosed earlier in survivors who tend to be highly active in screening and on the lookout for changes in their breasts.

For these reasons, reducing the risk of cancer in the second breast with measures such as a double mastectomy wouldn't affect overall survival rates for breast cancer.

Our hope is all women faced with these choices feel informed and empowered to make the right decision for them. This includes knowing overall survival isn’t improved with a bilateral mastectomy. This represents a change in thinking, and it is a big topic.

We know that words like overall survival compared to rates of recurrence can be confusing. We have a webinar all about surgical choices and what you need to know. 

Surgical decisions are extremely personal. If you would like to talk through your concerns or questions, our team of specialist breast nurses are here to help. You can phone our helpline during business hours. 

Simply call 0800 BC NURSE (0800 226 8773), it's free!