PRIMARY OBJECTIVES:~I. To assess the proportion of patients with any prostate specific antigen (PSA) reduction at 12 weeks (~3 months) in observation + white button mushroom (WBM) supplement arm and observation only arm (control arm). (Cohort 1) II. To assess relative change in PSA at 48 weeks (~12 months) from baseline with or without WBM treatment. (Cohort 2)~SECONDARY OBJECTIVES:~I. To evaluate, adverse events, PSA-response rate and time to PSA progression. (Cohort 1) II. To evaluate adverse events, time to initiation of additional therapy and progression. (Cohort 2)~EXPLORATORY OBJECTIVES:~I. To characterize the immunomodulatory effects of WBM supplement in serial blood samples. (Cohort 1) II. To assess the effect of therapy with WBM on sexual function. (Cohort 1) III. To assess the effect of WBM on Gleason grade in prostate cancer subjects on active surveillance. (Cohort 2) IV. To characterize the immunomodulatory effects of WBM supplement in serial blood samples and in tumor tissue. (Cohort 2) V. To characterize changes in cancer signaling pathways in tumor tissue after intake of WBM supplement. (Cohort 2) VI. To assess the effect of WBM supplement on sexual function. (Cohort 2)~OUTLINE: Patients are assigned to 1 of 2 cohorts.~COHORT I: Biochemically recurrent prostate cancer patients are randomized to 1 of 2 arms.~ARM IA: Patients receive white button mushroom extract orally (PO) twice daily (BID) on day 1. Treatment repeats every 4 weeks for cycles 1-3 then every 12 weeks for cycles 4-6 (36 weeks) in the absence of disease progression or unacceptable toxicity.~ARM IB: Patients undergo clinical observation for 12 weeks. If PSA continues to increase, patients have the option to receive the white button mushroom extract as in arm IA.~COHORT II: Therapy naive favorable risk prostate cancer patients are randomized to 1 of 2 arms.~ARM IIA: Patients receive white mushroom extract PO BID on day 1. Treatment repeats every 12 weeks for 4 cycles (48 weeks) in the absence of disease progression or unacceptable toxicity.~ARM IIB: Patients undergo active surveillance for 48 weeks.~After completion of study treatment, patients are followed up at 30 days.
This phase II trial studies how well white button mushroom supplement works in reducing prostate-specific antigen (PSA) levels in patients with prostate cancer that has come back (recurrent) or has favorable risk and has not undergone any therapy (therapy naive). PSA is a blood marker of prostate growth. White button mushroom supplement may affect PSA level, various parameters of immune system and levels of hormones that may have a role in prostate cancer growth.