Do changes in a high serum prostate-specific antigen level and the free/total prostate-specific antigen ratio after antibiotic treatment rule out biopsy and the suspicion of cancer?

To evaluate the impact of antibiotic treatment in patients with higher-than-normal prostate-specific antigen (PSA) levels in terms of changes both in total PSA and free/total (f/t) PSA ratios. Serum PSA and f/t PSA changes after antibiotic treatment in 85 patients with normal digital rectal examination but elevated age-adjusted serum PSA levels were evaluated with relevance to biopsy results. Serum PSA levels decreased after antibiotic treatment in 47 of 85 patients. The f/t PSA ratio decreased or remained unchanged in 21 and increased in 26 of these 47 cases. Cancer detection rate in the former group was 52.4% (11/21), while it was 7.7% (2/26) in the latter (p = 0.002). There were 38 patients with increased PSA levels after antibiotics. The f/t PSA ratios decreased or remained unchanged in 20 and increased in 18 of these 38 cases. Cancer detection rates were 55% (11/20) in the former and 16.7% (3/18) in the latter group (p = 0.003). The PSA and f/t PSA levels may change with long-term antibiotic treatment in patients with elevated PSA values. The f/t PSA ratio rather than total PSA appears to be more helpful in suggesting prostate cancer in these cases.