To explore whether the use of aspirin and SSRI, either as monotherapy or combined, can have a clinical benefit against colorectal cancer (CRC), the development of CRC involves multiple dysfunctional pathways. A nested-case control study using nationwide Swedish registers was carried out, recruiting 24,786 CRC cases and randomly matched to 74,358 controls, conditional on birth year and sex using incidence density sampling.
Odds ratios were calculated from the conditional logistic regression model. Additive interaction was calculated as a relative excess risk for interaction and multiplicative interaction was calculated by including a product term in the regression model.
Both aspirin and SSRIs monotherapy were negatively associated with CRC risk, but the combined use of both was associated with even lower CRC risk (OR 0.77), than aspirin monotherapy (adjusted OR 0.91), and SSRI monotherapy adjusted (OR 0.93).
A significant interaction was observed at the additive scale with a relative excess risk for the interaction of -0.07, whereas no interaction was noted on the interactive scale. The inverse associations of CRC with aspirin and SSRIs showed a dose-dependent pattern.
It was concluded that the study suggested that the use of aspirin and SSRIs, either as monotherapy or combined, was associated with a reduced risk of CRC, but requiring further studies to confirm underlying mechanisms and allowing plausibility of clinical recommendation.
Zhang, N., Sundquist, J., Sundquist, K., et al. “Combined Use of Aspirin and Selective Serotonin Reuptake Indicators is Associated with Lower Risk of Colorectal Cancer: A Nested Case-Control Study.” American Journal of Gastroenterology, 2021; Vol. 116, pp. 1313-1321.