Lumpectomy 'as effective as double mastectomy'

“Double mastectomy for breast cancer 'does not boost survival chances' – when compared to breast-conserving surgery," The Guardian reports.

The news is based on the results of a large US cohort study of women with early stage breast cancer in one breast.

It found that the 10-year mortality benefit associated with bilateral mastectomy (removal of both breasts) was the same as breast-conserving surgery (also known as lumpectomy, where the cancer and a border of healthy tissue is removed) plus radiotherapy.

Unilateral mastectomy (removal of the affected breast) was associated with a slightly increased risk of 10-year mortality, although the absolute difference was only 4%.

In the UK, bilateral mastectomy may be recommended for women at high risk of breast cancer due to family history, or because of a gene mutation (for example mutations in the BRCA1 and BRCA2 genes). A bilateral mastectomy can then be followed by breast reconstruction surgery, restoring the original look of the breasts.

Disadvantages of a bilateral mastectomy compared to a lumpectomy include a longer recovery time and a higher risk of complications.

This study suggests that bilateral mastectomy may not be associated with any significant survival benefit over breast conserving therapy plus radiotherapy for most women.

It is important to note that the outcome for individual patients may vary, and the type of surgery a woman with breast cancer receives will depend on a number of factors, including her personal wishes and feelings.

 

The study was carried out by researchers from Stanford University School of Medicine and the Cancer Prevention Institute of California. This study was funded by the Jan Weimer Junior Faculty Chair in Breast Oncology, the Suzanne Pride Bryan Fund for Breast Cancer Research at Stanford Cancer Institute, and the National Cancer Institute Surveillance, Epidemiology, and End Results Program. The collection of cancer incidence data was supported by the California Department of Health Services, the National Cancer Institute Surveillance, Epidemiology, and End Results Program and the Centres for Disease Control and Prevention National Program of Cancer Registries.

The study was published in the peer-reviewed medical journal JAMA. This article is open access so it is free to read and download.

The results of this study were well covered by the UK media. However, the headlines could be misconstrued as stating that there are no benefits associated with double mastectomies.

In fact, the headlines refer to the fact the double mastectomies weren’t associated with a significantly different survival benefit compared to breast-conserving therapy with radiotherapy, rather than with no survival benefit compared to no treatment.

 

This was a cohort study that aimed to better understand the use of and outcomes after different treatment options for women diagnosed with early stage unilateral breast cancer (cancer in one breast).

Treatment options for breast cancer include surgery, radiotherapy, chemotherapy, hormone therapy and biological treatments.

In this study, the researchers were interested in different surgical options: unilateral mastectomy (removal of the breast with the cancer), bilateral mastectomy (removal of both breasts) and breast-conserving therapy with radiotherapy.

As this is a cohort study it cannot show that the type of surgery was the cause of poorer outcomes. A randomised controlled trial would be required for this. However, the researchers state that as bilateral mastectomy is an elective procedure for unilateral breast cancer, women who want this option are unlikely to accept randomisation to a less extensive surgical procedure in a trial.

 

The researchers identified women who had been diagnosed with early stage breast cancer (stage 0-III cancer) in one breast between 1998 and 2011 from the California Cancer Registry. Stage 0 breast cancer is localised and non-invasive, while stage III cancer is invasive and has spread to the lymph nodes.

The researchers followed these women for an average of 89.1 months.

The researchers looked for factors associated with the women receiving different types of surgical treatment.

They then looked to see how many women had died, and how many women had died from breast cancer, to see if the risk was different for women who had received different surgical treatment options.

The researchers adjusted their analyses for the following confounders:

 

The researchers identified 189,734 women who had been diagnosed with stage 0-III cancer in one breast between 1998 and 2011 from the California Cancer Registry. Of these, 6.2% underwent bilateral mastectomy, 55.0% received breast-conserving surgery with radiotherapy and 38.8% had a unilateral mastectomy.

The percentage of women who received bilateral mastectomy increased from 2.0% in 1998 to 12.3% in 2011, an annual increase of 14.3%. The increase in bilateral mastectomy rate was greatest among women younger than 40 years: the rate increased from 3.6% in 1998 to 33% in 2011.

The researchers compared the 10-year mortality (the percentage of women who don’t survive for 10 years) of women who had received breast-conserving surgery with radiotherapy, unilateral mastectomy and bilateral mastectomy.

The researchers found that there was no significant mortality difference with bilateral mastectomy compared with breast-conserving surgery with radiotherapy (hazard ratio [HR] 1.02, 95% confidence interval [CI] 0.94 to 1.11), although unilateral mastectomy was associated with increased mortality (HR 1.35, 95% CI 1.32 to 1.39). The results for risk of death from breast cancer were similar.

The researchers also found that there were significant differences in the women who received the different surgical options.

Compared to women who received breast-conserving therapy plus radiotherapy, women were more likely to receive bilateral mastectomy if they:

Compared to women who received breast-conserving therapy plus radiotherapy, women were more likely to receive unilateral mastectomy if they:

 

The researchers concluded that “use of bilateral mastectomy increased significantly throughout California from 1998 through 2011 and was not associated with lower mortality than that achieved with breast-conserving surgery plus radiotherapy. Unilateral mastectomy was associated with higher mortality than were the other two surgical options”.

 

This large US cohort study of women with early stage breast cancer in one breast has found no 10-year mortality benefit associated with bilateral mastectomy (removal of both breasts) compared with breast-conserving surgery (also known as lumpectomy, where the cancer and a border of healthy tissue is removed) plus radiotherapy.

Unilateral mastectomy was associated with a slightly increased risk of 10-year mortality, although the absolute difference was only 4%.

However, as there were significant differences between the patients receiving the different surgical options it makes it likely that the increase in risk associated with unilateral mastectomy is due to incomplete adjustment for some of the measured factors, unmeasured factors (for example, the presence of other diseases such as diabetes), or differences in access to care.

This study suggests that bilateral mastectomy may not be associated with any significant survival benefit compared to breast-conserving surgery with radiotherapy for the population of women with unilateral breast cancer.

However, as this was a cohort study it cannot prove that there was no significant survival difference; this would require a randomised controlled trial.

It is important to note that the outcome for individual patients may vary, and the type of surgery a woman with breast cancer receives will depend on a number of factors, including her personal wishes and feelings.

Ultimately, if you have been told you may require breast surgery, the choice of surgery will be down to you. Questions you may wish to ask your surgeon include:

Read more about preparing for surgery.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

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