OBJECTIVES: To provide an overview of drugs used by elderly in the year before colon cancer diagnosis and to compare this with a matched control group without cancer. METHODS: Data were obtained from the population-based Netherlands Cancer Registry (NCR) and linked to the PHARMO Database Network, which includes complete longitudinal data obtained from out-patient pharmacies.

All colon cancer patients aged ≥70 years diagnosed between 2000-2011 were included. Patients were matched 1:1 with controls  on gender, year of birth and postal code. Differences in the proportion of users between cases and controls of each drug on WHO ATC-3 level were calculated using Chi tests. Drug use was defined in the year before colon cancer diagnosis or cohort entry date and during each quarter of that year. RESULTS: The study population consisted of 2,735 colon cancer patients and 2,735 matched cancer-free controls. 90% of cases and 69% of controls used ≥1 drug during the study period. The top 3 most frequently used drugs, based on the highest number of users among cases during the total year, were drugs for constipation (cases vs. controls 58% vs. 10%, p<0.0001), antithrombotic agents (42% vs. 33%, p<0.0001) and drugs for acid related disorders (35% vs. 22%, p<0.0001). For all 3 drugs, the number of users in each quarter was higher among cases. Among cases, the number of users increased during the last quarter of the year for drugs for constipation (10% Q3 to 53% Q4) and drugs for acid related disorders (19% Q3 to 27% Q4). CONCLUSIONS: Our study demonstrates higher drug use among elderly colon cancer patients during the year before diagnosis as compared to a matched cancer-free control group, which increased even more during the last three months before colon cancer diagnosis. The effect of specific drugs on cancer treatment and outcome should be subject of further study.