Efficacy of oral administration of cystine and theanine in colorectal cancer patients undergoing capecitabine-based adjuvant chemotherapy after surgery: a multi-institutional, randomized, double-blinded, placebo-controlled, phase II trial (JORTC-CAM03)

PURPOSE: Capecitabine-based adjuvant chemotherapy for colorectal cancer patients often causes adverse events (AEs), such as diarrhea, stomatitis, anorexia, and hand-foot syndrome (HFS). Cystine and theanine were reported to attenuate some chemotherapy-associated AEs, and hence are also expected to attenuate capecitabine-induced AEs. Therefore, we aimed to investigate the safety and efficacy of cystine/theanine treatment in colorectal cancer patients undergoing capecitabine-based adjuvant chemotherapy after surgery. METHODS: A total of 100 colorectal cancer patients treated with capecitabine as an adjuvant chemotherapy after surgery were randomly allocated into the cystine/theanine group (n = 52) or the placebo group (n = 48). The primary endpoint was incidence rate of diarrhea of grade 1 or higher in accordance with the Common Terminology Criteria for AEs (CTCAE) v.4.0, Japanese Clinical Oncology Group (JCOG) version. The secondary endpoints included incidence rates of other AEs (CTCAE v.4.0-JCOG), as well as the incidence rate of HFS according to the HFS grading scale. RESULTS: There were no significant differences in capecitabine-induced AEs between the two groups. However, the incidence rate of diarrhea of grade 1 or higher tended to be lower in the cystine/theanine group than the placebo group (18.4% vs. 28.9%, p = 0.169) as well as the incidence rate of HFS of grade 1 or higher (CTCAE v.4.0-JCOG or HFS grading scale) (67.4% vs. 77.8%, p = 0.185, 67.3% vs. 80.0%, p = 0.124, respectively). CONCLUSION: This trial demonstrated that cystine/theanine treatment of colorectal cancer patients undergoing capecitabine-based adjuvant chemotherapy after surgery is safe and has the tendency to reduce the incidence rate of diarrhea or HFS. TRIAL REGISTRATION: UMIN000024784 ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00520-019-05205-1) contains supplementary material, which is available to authorized users.