“The following meta-analysis is the next in a recently published series of papers by Ruth-Ann Marrie and colleagues. It suggests MSers have a higher incidence of urinary tract cancers and meningiomas than the general population. The higher incidence of meningiomas is likely to be explained by ascertainment bias; MSers are more likely to have MRI scans and hence small incidental meningiomas are more likely to be detected. Why would urinary tract and in particular bladder cancers be higher? This is probably due to the high incidence of bladder problems in MS and the resultant recurrent or chronic urinary tract infections. Bacterial metabolism and inflammation in the bladder drive genetic mutations in the cells lining the bladder, which increases the risk of getting bladder cancers. In addition, at one time cyclophosphamide, a chemotherapeutic drug, was commonly used to treat MS. One of the active breakdown products or metabolites of cyclophosphamide is concentrated and excreted in the urine. This metabolite is carcinogenic and may explain some of the historical risk of bladder cancer at a population level.”
“In summary, we need new and larger studies to assess whether or not MSers are at increased risk of getting cancer. The meta-analysis of published studies does not provide sufficient information.”
Marrie et al. A systematic review of the incidence and prevalence of cancer in multiple sclerosis. Mult Scler. 2015 Mar;21(3):294-304. Epub 2014 Dec 22.
BACKGROUND: Studies of cancer incidence and prevalence in MS have produced conflicting results.
OBJECTIVE: To estimate the incidence and prevalence of cancer in MSers and review the quality of included studies.
METHODS: We searched the PUBMED, SCOPUS, Web of Knowledge, and EMBASE databases, conference proceedings, and reference lists of all articles retrieved. Abstracts were screened for relevance by two reviewers. Data from included articles were captured using a standardized form, and the abstraction was verified by a second reviewer. We assessed quality of the included studies. We quantitatively assessed studies using the I 2 statistic, and conducted meta-analyses for population-based studies.
RESULTS: We identified 38 studies. Estimates for incidence and prevalence varied substantially for most cancers. In population-based studies, cervical, breast, and digestive cancers had the highest incidence. The risk of meningiomas and urinary system cancers appeared higher than expected, while the risks of pancreatic, ovarian, prostate and testicular cancer were lower than expected.