Multiple sclerosis (MS) is associated with a significantly lower overall survival and cancer-specific survival in patients diagnosed with colorectal cancer, particularly within the first 6 months following a cancer diagnosis, according to study findings published in Neurology.

In patients with MS, cancer is the second or third most common cause of death, following MS in the US. Previous research has indicated following a breast cancer diagnosis, women with MS have lower survival rates than women without MS. It’s unknown whether MS is associated with a lower survival rate in other types of common cancers, specifically colorectal cancer.

The objective of the current study was to compare overall survival and cancer-specific survival following a colorectal cancer diagnosis in patients with MS compared to patients without MS.

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The study used population-based administrative data from Canada and linked cancer registries to identify patients with colorectal cancer, all of whom were stratified as cases with MS (n=338) and without MS (n=1352). Patients with and without MS were matched 4:1 on year of birth, sex, year of cancer diagnosis, and region. Cox proportional hazards regression models were used to compare the 2 groups in terms all-cause survival. Additionally, a cause-specific hazards model was used to compare the cohorts in regard to cancer-specific survival.

The mean ages at cancer diagnosis were 64.6 years and 64.7 years in patients with MS vs without MS, respectively. In the adjusted analysis, MS was significantly associated with an elevated hazard of all-cause death, which the researchers noted was highest in the 6 months after diagnosis (hazard ratio [HR], 1.45; 95% CI, 1.19-1.76; P =.0002). The hazard for all-cause death declined following the 6-month mark (HR at 1 year, 1.34; 95% CI, 1.09-1.63, P =.004; HR at 2 years, 1.24; 95% CI, 0.99-1.56; HR at 5 years, 1.10; 95% CI, 0.80-1.50).

Patients with MS also had a higher hazard of cancer-specific death at the 6 months following the cancer diagnosis (HR, 1.29; 95% CI, 1.04-1.61; P =.02). In an analysis adjusted for cancer stage, the presence of MS was significantly associated with an increased hazard of death due to any cause (HR, 1.60; 95% CI, 1.16-2.21) as well as with cancer-specific death (HR, 1.47; 95% CI, 1.02-2.12). Adjustment for disability status partially attenuated the association of MS and all-cause death (HR, 1.37; 95% CI, 0.97-1.92) and cancer-specific death (HR, 1.34; 95% CI, 0.91-1.97).

The researchers wrote that they may have been unable to account for all comorbidities in the overall study cohort, despite using a comorbidity index that typically performs well in studies on cancer. Additionally, they note that they used a broad definition for cancer death, which may further limit their findings.

In conclusion, the researchers wrote that their findings have “potential implications for clinical decision-making and further study is warranted to determine what factors underlie these worse outcomes.”


Marrie RA, Maxwell C, Mahar A, et al. Colorectal cancer survival in multiple sclerosis: A matched cohort study. Neurology. Published online September 15, 2021. doi:10.1212/WNL.0000000000012634