Megestrol acetate improves appetite and abrogates weight loss in some patients with advanced cancer. Moreover, preliminary studies suggest that progestational agents down-regulate interleukin-6 (IL-6), an inflammatory cytokine widely implicated in cancer-associated anorexia and weight loss. The present investigation examined the effects of megestrol acetate on IL-6 in an attempt to confirm these earlier, preliminary studies. The translational component of a large multi-institutional trial, this investigation examined 85 patients with advanced cancer and weight loss. Patients had been randomly assigned to receive megestrol acetate liquid suspension 800 mg/day + placebo tablets, or oral dronabinol tablets 2.5 mg b.i.d. + liquid placebo, or both agents. Other testing included serial physician-reported weight and patient-reported appetite and global quality of life. We found no significant differences in 1-month changes in serum IL-6 according to whether patients had been treated with megestrol acetate, dronabinol, or the combination: the mean differences +/- standard deviation were -1.52+/-4.7 pg/ml, -0.62+/-3.5 pg/ml, and -0.2+/-3.1 pg/ml, respectively (P=0.40, by one-way ANOVA). Among the patients who noted alterations in their appetite over 1 month, we observed no significant changes in IL-6. Finally, changes in serum IL-6 were not associated with shifts in weight or global quality of life. Our investigation provides no evidence that megestrol acetate down-regulates IL-6 in patients with cancer-associated anorexia and weight loss.