Long-term prescribed drug use in stage I–III rectal cancer patients in Sweden, with a focus on bowel-regulating drugs after surgical and oncological treatment

Purpose To describe long-term prescribed drug use after rectal cancer treatment. Methods We identified 12,871 rectal cancer patients without distant metastasis between 2005 and 2016 and 64,341 matched population comparators using CRCBaSe (a Swedish nationwide register linkage of colorectal cancer patients). Mean defined daily doses (DDDs) of drug dispensing during relapse-free follow-up were calculated by Anatomical Therapeutic Chemical drug categories. Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) from negative binomial regression were used to compare drug dispensing between patients and comparators. Results The overall pattern of drug dispensing was similar among cancer survivors and comparators, although patients had higher mean DDDs of drugs regulating the digestive system. Excess dispensing of drugs for constipation (IRR, 3.35; 95% CI, 3.12–3.61), diarrhea (IRR, 6.43; 95% CI, 5.72–7.22), functional gastrointestinal disorders (IRR, 3.78; 95% CI, 3.15–4.54), and vitamin and mineral supplements (IRR, 1.37; 95% CI, 1.24–1.50) was observed up to 10 years after surgery. Treatment with Hartmann’s procedure was associated with higher dispensing rates of digestive drugs compared to surgery with anterior resection and abdominoperineal resection but the association was attributed to higher use of diabetic drugs. Additionally, excess digestive drug dispensing was associated with more advanced cancer stage but not with (chemo)radiotherapy treatment. Conclusions Excess drug use after rectal cancer is primarily driven by bowel-regulating drugs and is not modified by surgical or oncological treatment. Implications for Cancer Survivors The excess use of bowel-regulating drugs after rectal cancer indicated long-standing postsurgical gastrointestinal morbidity and need of prophylaxis. Reassuringly, no excess use of other drug classes was noted long term.