Antibiotics and observation have a similar impact on asymptomatic patients with a raised PSA

• To compare the influence of a 4-week course of empirical antimicrobial therapy or observation on the prostate-specific antigen (PSA) levels of asymptomatic patients with a raised baseline PSA. • To identify whether a decrease in PSA can predict the risk of prostate cancer (PCa) detection on prostate biopsy.

• Patients were referred to our ambulatory centre because of a raised PSA level (>2.5 ng/mL) with a normal digital rectal examination. A 12-core prostate biopsy was indicated in these patients and they were offered antibiotic treatment with levofloxacin 500 mg daily for 30 days. • Patients who did not agree to use antibiotics but who still showed interest in participating underwent simple observation, serving as controls. • Total and free PSA levels at baseline and after 45 days were measured. Variation in PSA level was calculated. • All patients underwent a 12-core prostate biopsy 6 weeks after the initial visit.

• In all, 245 men were enrolled, but 43 were lost due to follow-up. A total of 145 patients who used antibiotics and 57 controls were included in the analysis. • The median baseline PSA levels were 7.6 and 7.7 ng/mL in the antibiotic and control groups, respectively, with median follow-up levels of 6.8 and 7.0 ng/mL. The follow-up PSA level was significantly lower than the initial PSA level (P = 0.009). • Mean absolute and percentage variation in PSA level were similar in both groups (P = 0.828 and 0.128, respectively). • The overall PCa detection rate was 15.8%, and did not differ among the groups (P = 0.203). Regarding the percentage variation in PSA level, patients diagnosed with PCa tended to have their PSA level increased (22.4 vs -5.3%; P = 0.001). Indeed, a decrease of 20% in PSA was not predictive of a negative prostate biopsy (P = 0.41). • The area under the receiver operating characteristic curve for percentage PSA variation as a predictor of PCa was 0.660.

• PSA levels tend to fall when repeated after 45 days, regardless of antibiotic use. • Despite being associated with the chance of PCa, no percentage PSA variation threshold value exhibits satisfactory discriminatory properties.