BACKGROUND: The purpose of this pilot clinical trial was to evaluate the ability of Modified Citrus Pectin to influence the PSA slope in men with prostate cancer. MATERIALS AND METHODS: Patients who had either relapsed after or failed prior treatment for prostate cancer (PSA range 0.63 to 7.50) were given Modified Citrus Pectin (PectaSol®, EcoNugenics, Inc., San Rafael, CA 94901) at a dosage of 15 grams per day in three divided oral doses. PSA doubling time was calculated. RESULTS: A response (more than 30% lengthening of PSA doubling time) was seen in 4/7 patients (57%). One patient (1/7) had a partial response, one patient (1/7) had stable disease, and one patient (1/7) did not respond. Conclusion: Modified Citrus Pectin appears to lengthen the PSA doubling time in prostate cancer patients with low levels of PSA. Study responses are additionally compelling, as all study participants are still alive and capable of being evaluated for long-term follow-up, almost three years after completion of this study. More research involving larger numbers of patients is needed to fully define the role of MCP in prostate cancer treatment. Stephen Strum MD, Mark Scholz MD, Jon McDermed Pharm D, Michael McCulloch BA, Isaac Eliaz MD. International Conference on Diet and Prevention of Cancer, May 1999, Tampere, Finland.