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Sulforaphane treatment in men with recurrent prostate cancer.
J Clin Oncol 31, 2013 (suppl; abstr 5017)
Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).
Background: Diets high in cruciferous vegetables are strongly associated with lower prostate cancer risk. Sulforaphane is a constituent of these foods postulated to harbor the anti-neoplastic activity based on pre-clinical evidence in multiple tumor models. Our own work demonstrates that sulforaphane inhibits HDAC function and suppresses AR signaling in prostate cancer cells (Gibbs, et al PNAS 2009). However, the anti-tumor efficacy and safety of sulforaphane in men with prostate cancer was unknown. Methods: In this single arm study, we treated patients with biochemical (PSA)-recurrence of prostate cancer with 200 µmol of sulforaphane extracts for up to 20 weeks. The primary endpoint was PSA response rate (>50% decline in PSA). Other efficacy endpoints included: maximal PSA decline and percent change in PSA from baseline to end of study. We also analyzed PSA doubling time changes using a mixed effects model. Genotyping for GSTM1 that contributes to sulforaphane metabolism, sulforaphane pharmacokinetics (PK), and pharmacodynamic (PD) measurements of HDAC inhibition in mononuclear cells (MCs) were also performed. Results: Twenty patients were enrolled, and 16/20 (80%) completed the pre-planned 20 weeks of treatment. One patient experienced a PSA decline >50%. Thirty-five percent of patients had lesser PSA declines (3% to 20%), and 15% of patients had a final PSA lower than baseline. There was a significant reduction in PSA doubling time (6 months pre-study vs. 9.4 months on-study, p=.013). Of note, testosterone levels remained non-castrate in all subjects. PK analysis demonstrated that GSTM1 null genotype correlated with longer sulforaphane T1/2 (half-life) (2.6 hours for GSTM1 null vs. 2.1 hours for GSTM1 intact, p=0.04). Sulforaphane treatment also increased histone acetylation in PD assays in MCs. Finally, no grade three adverse events were seen, and only one patient discontinued study treatment for toxicity (grade one GI discomfort). Conclusions: Treatment with 200 µmol per day of sulforaphane is feasible, safe, and inhibits HDAC function. This combined with the preliminary observation of PSA modulation, which may indicate biologic activity, provides the basis for dose escalation studies of sulforaphane in men with prostate cancer. Clinical trial information: NCT01228084.
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