SSRIs associated with reduced risk of colorectal cancer, data suggest
Use of selective serotonin reuptake inhibitors is associated with a reduced risk of colorectal cancer, according to researchers in Canada (Lancet Oncology 2006;7:301). No consistent relationship between tricyclic antidepressants and risk of colon cancer was observed, they add.
Wanning Xu, McGill University, Montreal, Quebec, and colleagues conducted a population-based, nested case-control study. The SSRI population consisted of 3,367 cases and 13,468 controls and the tricyclic antidepressant population consisted of 6,544 cases and 26,176 controls.
Animal studies have previously suggested that SSRIs reduce the growth of colorectal cancer and that tricyclic antidepressants enhance carcinogenesis in the colon, the researchers explain. They therefore aimed to assess whether SSRI use was associated with a decreased risk of colorectal cancer and tricyclic use with an increased risk of colorectal cancer.
The researchers found that a decreased risk of colorectal cancer was associated with high daily SSRI intake 0–5 years before diagnosis, adjusted for sex, age, use of non-steroidal anti-inflammatory drugs and use of SSRIs during 6–10 years before diagnosis (incidence rate ratio 0.70, 95 per cent confidence interval 0.50–0.96; P for trend=0.0172). They suggest that SSRIs may have antipromoter or direct cytotoxic effects. No significant association between risk of colorectal cancer and use of any tricyclic antidepressant was recorded, they add.
Possible causes of colorectal cancer, such as unhealthy lifestyle and diet, were not adjusted for, say the researchers. “Future studies should have a more complete assessment of confounders, including lifestyle and dietary habits, use of other drugs such as statins and the presence of comorbidity such as diabetes and inflammatory bowel disease,” they suggest.
The author of an accompanying editorial (ibid, p277) comments that the data provide interesting insights but, until further trial data are available, clinicians should not consider SSRI use solely for chemopreventive purposes.