A phase Ib trial of mushroom powder in biochemically recurrent, hormone-naive prostate cancer.

Abstract

142 Background: Biochemically recurrent prostate cancer (PC) is a common presentation of relapse after primary local therapies. Strategies to delay disease progression and defer initiation of androgen deprivation therapy and associated side effects are needed. White button mushroom (WBM, Agaricus bisporus) extract suppresses prostate cancer tumor growth in animals, and prior human experience indicates favorable toxicity profile. Methods: Patients (pts) with rising PSA of ≥0.2 ng/mL after prostatectomy (RP) and/or radiation (RT) and no radiographic evidence of metastases were treated with WBM powder tablets at 4, 6, 8, 10, 12 and 14 grams po daily. Dose escalation was conducted in cohorts of 6 and continued as long as no more than 1 patient per cohort experienced dose limiting toxicity (DLT). Therapy continued until PSA increased by ≥100% and by ≥1 ng/mL, or clinically detectable metastases or unacceptable toxicity occurred. Primary objective was feasibility and toxicity, secondary objective was the effect of WBM on serum PSA and androgen levels. Results: Thirty six pts were treated. Median age was 68 (53-80).Thirty three pts (92%) had prior RP and all underwent previous RT. Median PSA was 1.9 (0.2-22.2). Mean compliance was 98.6 %. No DLT’s were encountered. The most common side effect was grade 1 abdominal bloating (39%); one patient experienced asymptomatic grade 3 hyponatremia. Overall PSA response rate was 11% (95% CI: 4%-27%). Two pts receiving 8 and 14 gm/day demonstrated a PSA complete response (CR), defined as a decline in PSA to undetectable levels that continues for 26 and 7 months respectively. Two pts, receiving 8 and 14 gm/day, experienced confirmed PSA partial responses (PR), defined as a ≥50% PSA decline on treatment. After 3 months of therapy 36% of pts (13/36) demonstrated some PSA decrease below baseline. No association between PSA response and serum testosterone, DHT or DHEA levels was observed. Median duration on therapy is 10.2 months (0.9 – 35.3). Ten pts remain on therapy. Conclusions: Therapy with WBM was well tolerated. Our data suggest that WBM intake results in durable decreases in PSA level in some patients with biochemically recurrent PC. Further studies to clarify mechanism of action are warranted. Clinical trial information: NCT00779168.