A phase I trial of mushroom powder in patients with biochemically recurrent prostate cancer: roles of cytokines and myeloid-derived suppressor cells (MDSCs) for Agaricus bisporus induced PSA responses
BACKGROUND
Each year in the U.S., nearly 50,000 prostate cancer patients exhibit a rise in PSA levels, which can indicate disease recurrence. For patients (pts) with biochemically recurrent prostate cancer (PC), we evaluated the effects of white button mushroom (WBM) powder on serum PSA levels; also, the tolerability and biological activity of WBM was determined.
METHODS
Pts with continuously rising PSA levels were enrolled. Dose escalation was conducted in cohorts of 6; this continued provided that no more than one patient per cohort experienced dose limiting toxicity (DLT). The primary objective was to evaluate treatment feasibility and associated toxicity. The secondary objectives were to determine the effect of WBM on both serum PSA and androgen levels; and evaluate WBM’s impact on myeloid-derived suppressor cells (MDSCs) and cytokine levels.
RESULTS
Thirty-six pts were treated; no DLT’s were encountered. Overall PSA response rate was 11%. Two pts receiving 8 and 14 gm/day demonstrated a PSA complete response (CR): their PSA declined to undetectable levels that continue for 49 and 30 months. Two pts, receiving 8 and 12 gm/day, experienced a PSA partial response (PR). After 3 months of therapy, 36% of pts (13/36) experienced some PSA decrease below baseline. Pts with PSA CR and PR demonstrated higher levels of baseline interleukin-15 (IL-15) than nonresponders; for this group, we observed therapy-associated declines in myeloid-derived suppressor cells (MDSCs).
CONCLUSIONS
Therapy with WBM appears to both impact PSA levels and modulate the biology of biochemically recurrent PC by decreasing immunosuppressive factors.
