PSA Calculations and Interpretation for Patients on Dutasteride

Calculations

The free-to-total PSA ratio is calculated as free PSA divided by total PSA, which in this case is 0.21 divided by 1.38, resulting in 0.152 or 15.2%, according to the National Comprehensive Cancer Network 1
PSA density can be calculated using the current PSA value or the doubled PSA value for patients on dutasteride, with the current PSA value being 1.38 ng/mL and the doubled PSA value being 2.76 ng/mL, resulting in PSA densities of 0.055 ng/mL/cc and 0.11 ng/mL/cc, respectively, as recommended by the National Comprehensive Cancer Network 2, 3

A free-to-total PSA ratio of 15.2% is at the borderline threshold for cancer risk, with the FDA-approved cutoff of 25% detecting 95% of prostate cancers while avoiding 20% of unnecessary biopsies in the 4-10 ng/mL total PSA range, according to the National Comprehensive Cancer Network 1, 2, 3
A PSA density cutoff of 0.15 ng/mL/cc is recommended to spare up to 50% of men from unnecessary biopsies, with both calculated PSA density values being reassuring, as stated by the National Comprehensive Cancer Network 2, 3
The doubled PSA of 2.76 ng/mL falls in the 2.5-4.0 ng/mL range, where prostate cancer incidence is approximately 24.5% on biopsy, according to the American Urological Association 4, 5

No immediate biopsy is indicated based on these values alone, with the PSA density being reassuring and the free-to-total PSA ratio being at the borderline but not definitively concerning, as recommended by the National Comprehensive Cancer Network 1, 2, 3
Consider prostate biopsy if any of the following are present: abnormal digital rectal examination findings, PSA density greater than 0.15 ng/mL/cc, or prostate volume less than 40 cm³, according to the National Comprehensive Cancer Network 1
Close monitoring with serial PSA measurements is appropriate if the digital rectal examination is normal and no other concerning features are present, with any confirmed increase from the lowest PSA value while on dutasteride potentially signaling the presence of prostate cancer, as recommended by the American Urological Association 4, 5