Prostate cancer patients undergoing localized external beam radiation therapy (EBRT) can experience a progressive increase in fatigue, which can affect physical functioning and quality of life. The purpose of this study was to develop a mouse EBRT prostate cancer treatment model with which to determine the role of pro-inflammatory cytokines in the genesis of EBRT-related fatigue. We assessed voluntary wheel-running activity (VWRA) as a proxy for fatigue, food intake and body weight in male C57BL/6 mice undergoing EBRT to the pelvis. In the first experiment, anesthetized male C57BL/6 mice underwent fractionated EBRT to the pelvis for a total dose of 68.2 Gy, thereby mimicking a clinically relevant therapeutic dose and frequency. The day after the last treatment, levels of IL-1β and TNF-α in plasma along with mRNA levels in liver, colon and whole brain were measured. EBRT-induced fatigue resulted in reduced body weight, diminished food intake, and increased plasma and tissue levels of IL-1β and TNF-α. In a follow-up experiment, we used TNF-α-deficient mice to further delineate the role of TNF-α signaling in EBRT-induced sickness behavior. EBRT-induced changes in fatigue, food intake and body weight were no different between TNF-α deficient mice and their wild-type counterparts. Taken together our data demonstrate that a clinically relevant localized irradiation of the pelvis induces a systemic IL-1β and TNF-α response and sickness behavior in mice, but the TNF-α signaling pathway alone does not independently mediate these effects.

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