MS may decrease all-cause survival among women with breast cancer

Women with MS and breast cancer experienced decreased overall survival compared with women who had breast cancer but not MS, according to findings from a matched cohort study published in Neurology.

However, when the researchers looked only at cancer-specific mortality, they found that survival rates did not change between patients with and without MS.

“Although MS and its complications remain the most common cause of death in people with MS, cancer is the second or third most common cause of death,” Ruth Ann Marrie, MD, PhD, FRCPC, professor in the departments of internal medicine and community health sciences and director of the MS clinic at the University of Manitoba in Canada and American Academy of Neurology member, said in a press release.

Marrie and colleagues investigated the survival rates of women with and without MS after a breast cancer diagnosis. The retrospective, population-based, cohort study included 779 women with both MS and breast cancer and 3,116 women with only breast cancer in Manitoba and Ontario between January 1, 1994, and December 31, 2016. The researchers extracted data from Canadian health databases and selected at least four breast cancer patients without MS matched by birth year, cancer diagnosis year and region for every patient with MS and breast cancer. They compared all-cause survival between the two cohorts using Cox proportional hazards regression, adjusting for age at cancer diagnosis, cancer diagnosis period, income bracket, region and Elixhauser comorbidity score. Marrie and colleagues also looked at cancer-specific survival between cohorts using a multivariable cause-specific hazards model.

The mean age among all women included in the study at the time of their breast cancer diagnosis was 57.8 years, with a majority in both cohorts receiving a stage 1 or stage 2 diagnosis. The researchers found that, after adjusting for covariates, MS correlated with a 28% increased risk for all-cause mortality (HR = 1.28; 95% CI, 1.08-1.53). However, MS was not associated with altered cancer-specific survival (HR = 0.98; 95% CI, 0.65-1.46). Stratification by cancer stage did not alter the associations between patients with MS and the matched cohort regarding death from any cause (HR = 1.32; 95% CI, 0.99-1.77) or cancer-specific death (HR = 1.18; 95% CI, 0.84-1.67).

The overall mortality rate for all women with MS was 3.79 (95% CI, 3.21-4.36) vs. 2.98 (95% CI, 2.73-3.23) for matched controls.

“Because our study looked at women only in Canada, future studies are needed to confirm these findings in women in other countries and identify the factors specifically related to MS that are associated with worse outcomes,” Marrie said in the release.

Reference:

American Academy of Neurology. Does MS affect women’s survival rate after breast cancer diagnosis? Available at: https://www.aan.com/AAN-Resources/Details/press-room/. Accessed May 19, 2021.