Double mastectomy reduces risk of second cancer, but not mortality

Offered as a preventive measure to women with unilateral breast cancer, bilateral mastectomy may not be as beneficial as some people think. A study of 108,000 women suggests that it does not improve long-term survival.In JAMA Oncology, researchers at Women's College Hospital in Toronto compared three groups of women with unilateral breast cancer according to the treatment received: unilateral mastectomy, bilateral mastectomy or lumpectomy. One-third of patients had received chemotherapy and two-thirds had received radiotherapy.In participants who had undergone unilateral mastectomy or lumpectomy, the 20-year cumulative risk of developing contralateral breast cancer rose to 6.9%. This risk increased by only 0.7% for those who had both breasts removed. This type of surgery would therefore significantly reduce the risk of cancer in the second breast. The risk of death was also observed to be four times higher in patients who developed cancer in the contralateral breast, and up to 10 times higher in those with ductal carcinoma in situ.Paradoxically, this did not translate into lower mortality rates for those who had both breasts removed preventively. They had surprisingly similar 20-year mortality rates compared to unilateral mastectomy or lumpectomy, at around 16% for all three types of treatment. Preventing contralateral cancer by bilateral mastectomy would not guarantee a better survival rate for women.These findings raise crucial questions about the origin of this type of breast cancer. “Contralateral breast cancer is often thought of as a new primary tumour likely to metastasize. Our results challenge this interpretation. If the increase in death after contralateral breast cancer were truly attributable to metastasis of this new cancer, we would have expected bilateral mastectomy to be beneficial,” the researchers note. Treatment effectivenessThe appearance of the contralateral cancer would be more the manifestation of a risk already present in the patient, rather than the cause of this high mortality risk. This hypothesis remains to be confirmed, but it could be a sign that treatment of the initial cancer was not as effective as expected. This observation had already been made by researchers in 1991, who looked at ipsilateral breast cancer recurrence. At the time, they recommended lumpectomy as the preferred treatment for breast cancer, since more aggressive breast surgery did not appear to increase survival rates.Certain data were not included in the analyses, notably those concerning family history, the use of endocrine therapy or the presence of BRCA1 or BRCA2 variations. Excluding these risk factors could alter the results.

Double mastectomy reduces risk of second cancer, but not mortality

Register for free access or login.

Related Topics