The role of cytokines and Indolamine-2.3 dioxygenase in experiencing a psycho-neurological symptom cluster in hematological cancer patients: IL-1alpha, IL-1beta, IL-4, IL-6, TNF-alpha, kynurenine, and tryptophan.

OBJECTIVE: This study examined (a) whether there are a subgroup of cancer patients experiencing the selected psycho-neurological symptoms as a cluster (depression, cognitive impairment, fatigue, sleep disturbance, and pain); (b) whether demographic and clinical characteristics and pro-inflammatory cytokines (IL-1α, IL-1ß, IL-4, IL-6, TNF-alpha) are associated with subgroup membership; and (c) whether the activity of indolamine-2.3 dioxygenase(IDO) is associated with pro-inflammatory cytokine activity and psycho-neurological symptom cluster experience. METHODS: This was a prospective cohort study where 149 hematologic patients were recruited from a university hospital and 65 healthy volunteers provided control data. Latent profile analyses were conducted to identify subgroups at two time points: the last day of chemotherapy and 1 week after chemotherapy completion. Influencing factors of subgroup membership were examined by logistic regression. RESULTS: A substantial number of patients (33%, 34% at each time point) experienced the selected psycho-neurological symptoms as a cluster. Older age and elevated IL-1α and IL-6 were associated with experiencing the psycho-neurological symptom cluster. IDO activity was higher in the patients experiencing psycho-neurological symptom cluster; and was positively associated with IL-6. Symptom severity, IL-1α, IL-6, and IDO activity were all significantly higher in cancer patients than in the healthy controls. The findings were preserved across time points. CONCLUSIONS: The activation of pro-inflammatory cytokines and their cross-talk with IDO may be a common biological mechanism, underlying a psycho-neurological symptom cluster experience. The novel approaches for symptom assessment and management can be developed by assessing multiple psycho-neurological symptoms as a cluster and by targeting their common biological pathway.