PSA fall after antibiotics does not indicate absence of prostate cancer
MedWire News: Patients with type IV prostatitis and high prostate-specific antigen (PSA) levels are equally likely to show a decrease in the marker whether they receive antibiotics or placebo, researchers report.
Furthermore, men who do show a decrease in PSA after antibiotics or placebo are not at reduced risk of being diagnosed with prostate cancer on subsequent biopsy, report Rua Votorantim, (State University of Campinas, Brazil) and colleagues.
The researchers studied 200 men between 50 and 75 years old with a PSA of between 2.5–10.0 ng/dl. Of these men, 98 had a diagnosis of type IV prostatitis. In a prospective, double-blind trial these 98 men were randomly assigned to receive placebo or antibiotics twice a day for 4 weeks.
Among patients who received placebo, 29 (59.2%) patients showed a decrease in PSA and nine (31%) had cancer on biopsy. Among patients who received antibiotics, 26 (53.1%) patients showed a decrease in PSA and seven (26.9%) had cancer on biopsy. There was no statistical difference in either group in relation to PSA decrease after treatment or the presence of tumor.
Stopiglia et al comment in the Journal of Urology: “This study shows that antimicrobial therapy was no more effective than placebo in reducing PSA, and that the proportion of patients with cancer was similar in both groups (at least a third). More studies and larger samples should be conducted to confirm our data.”
In an accompanying editorial, Sumer Baltaci (Ankara University School of Medicine, Turkey) commented: “Considering the power calculation above 80%, the sample size should be at least 130 patients (65 in each group). Therefore, the results should be read cautiously.”
He said: “As recent studies have revealed percent free PSA to be more helpful in suggesting prostate cancer after antibiotic treatment, future studies should include such PSA parameters.”
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By James Taylor