Bilateral mastectomy in breast cancer does not lower death risk, finds study

USA: Bilateral mastectomy -- a procedure generally performed to treat or prevent breast cancer -- although reduce the risk of second breast cancer but does not lower the risk of cancer-associated death versus breast‐conserving therapy, a recent study published in the journal Cancer has found. Bilateral mastectomy (BLM) is the surgical removal of both breasts. It is usually recommended when cancer is present in both breasts or as a preventive measure for high-risk patients.

Increasingly, patients with breast cancer undergo BLM but the magnitude of its benefit is still unknown. Allison W. Kurian, Stanford University School of Medicine, Stanford, California, and colleagues measured relative risks of second contralateral breast cancer (CBC) and breast cancer death in breast cancer patients treated with BLM versus breast‐conserving therapy including surgery and radiotherapy (BCT) or unilateral mastectomy (ULM).

For the purpose, they followed 245,418 patients for 6.7 years, out of which 7784 patients (3.2%) developed contralateral breast cancer (CBC). The researchers used data from the Surveillance, Epidemiology, and End Results (SEER) program regarding all women diagnosed with American Joint Committee on Cancer stage 0 to stage III unilateral breast cancer in California from 1998 through 2015 and treated with BLM versus breast‐conserving therapy including surgery and radiotherapy (BCT) or unilateral mastectomy (ULM).

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Key findings of the study include:

• Relative risks were lower after BLM (hazard ratio [HR], 0.10) and higher after ULM (HR, 1.07) versus BCT.


• Absolute excess risks were higher after BCT and ULM (5.0 and 13.6 more cases, respectively) compared with BLM (28.6 fewer cases).


• BLM reduced risk more among older women (38.0 fewer cases for women aged ≥50 years vs 17.9 fewer cases among women aged <50 years) but provided similar risk reduction across categories of tumor grade and tumor hormone receptor status.


• Compared with BCT, the risk of breast cancer death was equivalent after BLM (HR, 1.03) and higher after ULM (HR, 1.21).

"Bilateral mastectomy may reduce second breast cancer risk by 34 to 43 cases per 10,000 person‐years compared with other surgical procedures, but is not associated with a lower risk of death," wrote the authors. "Second breast cancers are rare, and their reduction should be weighed against the harms associated with BLM, wrote the authors.

The study, "Magnitude of reduction in risk of second contralateral breast cancer with bilateral mastectomy in patients with breast cancer: Data from California, 1998 through 2015," is published in the journal Cancer.

DOI: https://doi.org/10.1002/cncr.32618