Relationship between fatigue, sleep quality and inflammatory cytokines during external beam radiation therapy for prostate cancer: A prospective study

Abstract

Background and purpose: Mechanisms of fatigue reported during radiotherapy are poorly defined but may include inflammatory cytokines and/or sleep disturbances. This prospective, longitudinal, phase II study assessed fatigue, sleep, and serum cytokine levels during radiotherapy for early-stage prostate cancer (PCa).

Material and methods: Twenty-eight men undergoing radiotherapy for early-stage PCa wore an Actiwatch Score to record fatigue level, sleep time, onset latency, efficiency and wake after sleep onset. Serum levels of IL-1α, IL-1β, TNF-α, IL-6, IL-8, IL-10 and VEGF were measured weekly during radiotherapy. Patient reported quality of life (QOL) metrics were collected before and after treatment. Linear mixed effects models examined trajectories across treatment weeks.

Results: Fatigue increased across treatment weeks (P<.01), and fatigue was associated with decreased patient-reported QOL. Sleep efficiency increased across treatment weeks (rate of change over time=.29, P=.03), and sleep onset latency decreased (rate of change over time=.86, P=.06). IL-6 tended to increase during treatment (P=0.09), but none of the cytokine levels or sleep variables were significantly related to fatigue trajectories.

Conclusions: Despite increased sleep efficiency across treatment weeks, fatigue significantly increased. Although IL-6 increased during the course of radiotherapy, cytokines levels were not associated with fatigue scores or sleep disturbance. Further studies are needed to define the mechanisms for fatigue during radiotherapy.

Keywords: Cancer treatment related fatigue; Cytokines; Prosate Cancer; Radiotherapy; Sleep disturbance.