Usefulness of a pharmacist outpatient service for S-1 adjuvant chemotherapy in patients with gastric cancer

S-1 adjuvant chemotherapy is an outpatient treatment for gastric cancer. To evaluate the role of the pharmacist outpatient service in increasing medication adherence and reducing adverse events associated with S-1, the present study retrospectively analyzed prescription recommendations from pharmacists to physicians and the persistence rate of S-1 adjuvant chemotherapy use in patients with gastric cancer. A total of 40 subjects who utilized the pharmacist outpatient service between November 2014 and March 2016 comprised the pharmacist group; and 94 patients who underwent S-1 adjuvant chemotherapy for gastric cancer between September 2012 and October 2014, but not as pharmacist outpatients, comprised the control group. Data on the prescription recommendations, persistence rate of S-1 adjuvant chemotherapy for 1 year and relative dose intensity were collected. The number of interventions and consultations for the pharmacist outpatient group were 40 and 644, respectively. Prescription recommendations regarding dosage, drug administration interval, and supportive therapy were provided in 62, 15 and 132 cases, respectively. The prescription proposal acceptance rate was 92.5%. The persistence rate of S-1 adjuvant chemotherapy for 1 year was significantly higher in the pharmacist group (82.5%) compared with the control group (39.4%; P<0.0001). The discontinuation rate due to adverse events was significantly lower in the pharmacist group (7.5%) compared with the control group (31.9%; P=0.0015). In subjects who completed S-1 adjuvant chemotherapy, the relative dose intensities in the control and pharmacist groups were 82.9 and 84.7%, respectively. In conclusion, the continued pharmaceutical intervention ensured a high persistence rate of S-1 adjuvant chemotherapy.