Prostate Cancers Detected During 5α-Reductase Inhibitor Use Are Smaller, De-Differentiated, But Confined when Compared To Controls

Rationale: To compare cancers detected during use of 5α-reductase inhibitors (5αRI) with cancers detected in untreated controls stratified for tumor size. Methods: Prostate biopsies were performed on 235 consecutive patients “for cause” (elevated or rising PSA, positive digital rectal examination, or focal hypoechoic lesion). Fifty patients were excluded for a prior diagnosis of cancer, leaving 185 as the study group (5αRI=41, control=144). Patients in the 5αRI group had been treated for a mean of 3.5 years. Cancer was ultimately diagnosed in 114/185 patients. Results: Cancer was diagnosed in 31/41 (76%) of patients treated with 5αRI and 83/144 (58%) of the control group (p=0.04). Control tumors were larger (14.3 mm) than those in 5αRI treated patients (9.4 mm, p=0.0007). No differences in mean PSA or PSA kinetics were detected between groups. For tumors less than 1.0 cm, the proportion of high grade cancers (Gleason 7-10 and Gleason 4+3-10) was higher in 5αRI subjects than in controls (p<0.05). Fewer 5αRI patients had proven extracapsular extension than controls, but this difference did not reach statistical significance (p=0.13). Normal DNA ploidy was more likely to be diagnosed in the 5αRI group versus controls, but this difference was not statistically significant (81% vs. 65%, p=0.14). Conclusions: Cancers diagnosed in patients presenting “for cause” treated with 5αRI drugs are more likely to be de-differentiated compared to controls. However, these tumors are also smaller and less likely to have extracapsular extension and abnormal DNA ploidy than controls.