124. Fatigue, affective symptom burden and altered tryptophan and phenylalanine metabolism in colorectal cancer patients undergoing chemotherapy

Patients with colorectal cancer (CRC) report debilitating fatigue that is caused by both disease and chemotherapy. An inflammatory mechanism for fatigue and affective symptoms has been proposed in cancer patients. This prospective study investigated tryptophan and tyrosine metabolism and symptom severity in 33 CRC patients undergoing oxaliplatin-based chemotherapy. During the 12-week study, patients rated symptom severity weekly using the M.D. Anderson Symptom Inventory (MDASI). Serum samples were collected before and after 3 and 6 chemotherapy cycles. Fatigue was the most severe patient-reported symptom before and during chemotherapy. Non-parametric generalized regression models were used to assess correlations between symptom severity and markers of guanosine triphosphate cyclohydrolase 1 (GTP-CH1) and indoleamine-2,3-dioxygenase (IDO) activity. At week 12, the kynurenine/tryptophan ratio was significantly associated with fatigue and sadness (both p