Incidence of opioid‐induced constipation in Japanese patients with cancer pain: A prospective observational cohort study

This multicenter, prospective, observational cohort study assessed opioid induced constipation (OIC) in Japanese patients with cancer. Eligible patients had stable cancer and an ECOG PS of 0‐2. OIC incidence based on the Rome IV diagnostic criteria was determined by patient diary entries during the first 14 days of opioid therapy. The proportion of patients with OIC was calculated for each 1‐week period and the overall 2‐week study period. Secondary measurements of OIC included the Bowel Function Index (BFI) score (patient assessment administered by physician), spontaneous bowel movements (SBMs) per week (patient assessment), and physician assessments. Medication for constipation was allowed. Two hundred and twenty patients were enrolled. The mean morphine‐equivalent dose was 22 mg/day. By Rome IV criteria, the cumulative incidence of OIC was 56% (95% CI: 49.2%‐62.9%); week 1, 48% (95% CI: 40.8%‐54.6%); week 2, 37% (95% CI: 30.1%‐43.9%). The cumulative incidence of OIC was lower in patients who received prophylactic agents for constipation (48% [95% CI: 38.1%‐57.5%]) than in patients who did not (65% [95% CI: 55.0%‐74.2%]). The cumulative incidences of OIC were 59% (95% CI: 51.9%‐66.0%), 61% (95% CI: 54.3%‐68.1%), and 45% (95% CI: 38.0%‐51.8%) based on BFI scores, physician assessments, and SBM frequency, respectively. Frequency of BMs/week before starting opioids was the most influential factor for the occurrence of OIC. Utilization of prophylactic agents for constipation was associated with a modest effect on reducing the incidence of OIC. The incidences of OIC reported were variable depending on the diagnostic tool involved.