Dietary manipulation, ethnicity, and serum PSA levels.

OBJECTIVES: To examine whether a diet low in fat and high in fiber, fruits, and vegetables and ethnicity had any influence on serum prostate-specific antigen (PSA) levels, because serum PSA is a marker for the presence of prostate cancer. The incidence of prostate cancer increases with age, varies by ethnicity, and is greater among men with a first-degree relative who has had the disease. Large international variations in the rates of prostate cancer incidence and mortality, as well as the incidence changes in migrants and their offspring, also suggest that exogenous factors, including diet, have a strong influence on the development of this disease. METHODS: We used data and blood samples from the Polyp Prevention Trial, a multicenter randomized trial designed to evaluate the impact of a diet low in fat and high in fiber, fruits, and vegetables on the recurrence of colorectal adenomas. Recruitment was from 1991 through 1994. Participants were followed up from their baseline recruitment date for 4 years. From this group, we identified 1100 white men and 97 black men who were 35 years of age or older, did not have prostate cancer, and had serum samples available for study. RESULTS: At baseline, no difference was present in the fat intake for the black and white men (mean +/- SE, 90 +/- 3.6 g/day and 84 +/- 1.0 g/day, respectively; P = 0.15). The baseline serum PSA levels did not vary by ethnicity. For black men, the mean serum PSA level was 2.2 +/- 0.36 ng/mL compared with 2.0 +/- 0.07 ng/mL for white men (P = 0.64). Although all men assigned to the intervention group markedly reduced their fat intake by approximately 15% and increased their fruit and vegetable intake by approximately 2.25 servings per day, no difference was noted in the kinetics of the serum PSA levels by dietary intervention or race. CONCLUSIONS: Although ethnic differences in the incidence of prostate cancer are well defined, we found no difference in the baseline fat intake among black and white men that might have contributed to this difference. Serum PSA, a marker often used in early detection programs for prostate cancer, was not associated with manipulation of the amount of fat in the diet, regardless of ethnicity.

Variation of serum prostate-specific antigen levels: an evaluation of year-to-year fluctuations.

CONTEXT: Serum prostate-specific antigen (PSA) testing is frequently used in early detection programs for prostate cancer. While PSA testing has resulted in an increase in prostate cancer detection, its routine use has been questioned because of a lack of specificity. OBJECTIVE: To determine whether year-to-year fluctuations in PSA levels are due to natural variation and render a single PSA test result unreliable. DESIGN, SETTING, AND PARTICIPANTS: Retrospective analysis of an unscreened population of 972 men (median age, 62 years) participating in the Polyp Prevention Trial (1991-1998). Five consecutive blood samples were obtained during a 4-year period and were assessed for total and free PSA levels. MAIN OUTCOME MEASURE: Abnormal PSA test result based on a PSA level higher than 4 ng/mL; a PSA level higher than 2.5 ng/mL; a PSA level above the age-specific cutoff; a PSA level in the range of 4 to 10 ng/mL and a free-to-total ratio of less than 0.25 ng/mL; or a PSA velocity higher than 0.75 ng/mL per year. RESULTS: Prostate biopsy would have been recommended in 207 participants (21%) with a PSA level higher than 4 ng/mL; in 358 (37%) with a level higher than 2.5 ng/mL; in 172 (18%) with a level above the age-specific cutoff; in 190 (20%) with a level between 4 and 10 ng/mL and a free-to-total ratio of less than 0.25 ng/mL; and in 145 (15%) with a velocity higher than 0.75 ng/mL per year. Among men with an abnormal PSA finding, a high proportion had a normal PSA finding at 1 or more subsequent visits during 4-year follow-up: 68 (44%) of 154 participants with a PSA level higher than 4 ng/mL; 116 (40%) of 291 had a level higher than 2.5 ng/mL; 64 (55%) of 117 had an elevated level above the age-specific cutoff; and 76 (53%) of 143 had a level between 4 and 10 ng/mL and a free-to-total ratio of less than 0.25 ng/mL. CONCLUSION: An isolated elevation in PSA level should be confirmed several weeks later before proceeding with further testing, including prostate biopsy.

Lack of effect of a low-fat, high-fruit, -vegetable, and -fiber diet on serum prostate-specific antigen of men without prostate cancer: results from a randomized trial.

PURPOSE: To determine whether a diet low in fat and high in fruits, vegetables, and fiber may be protective against prostate cancer by having an impact on serial levels of serum prostate-specific antigen (PSA). METHODS: Six hundred eighty-nine men were randomized to the intervention arm and 661 to the control arm. The intervention group received intensive counseling to consume a diet low in fat and high in fiber, fruits, and vegetables. The control group received a standard brochure on a healthy diet. PSA in serum was measured at baseline and annually thereafter for 4 years, and newly diagnosed prostate cancers were recorded. RESULTS: The individual PSA slope for each participant was calculated, and the distributions of slopes were compared between the two groups. There was no significant difference in distributions of the slopes (P =.99). The two groups were identical in the proportions of participants with elevated PSA at each time point. There was no difference in the PSA slopes between the two groups (P =.34) and in the frequencies of elevated PSA values for those with elevated PSA at baseline. Incidence of prostate cancer during the 4 years was similar in the two groups (19 and 22 in the control and intervention arms, respectively). CONCLUSION: Dietary intervention over a 4-year period with reduced fat and increased consumption of fruits, vegetables, and fiber has no impact on serum PSA levels in men. The study also offers no evidence that this dietary intervention over a 4-year period affects the incidence of prostate cancer during the 4 years.