A 48-year-old man has total PSA 3.1 ng/mL and free PSA 0.3 ng/mL. What does this suggest?

A 48-year-old man has total PSA 3.1 ng/mL and free PSA 0.3 ng/mL. What does this suggest?

• A. Both are normal
• B. Benign prostatic hypertrophy
• C. Increased risk of prostate cancer
• D. Free PSA is low and does not correlate

Answer: (C)

The key idea is that the relationship between free PSA and total PSA helps distinguish cancer from benign conditions when PSA is elevated. Total PSA is 3.1 ng/mL, and free PSA is 0.3 ng/mL, giving a free-to-total PSA ratio of about 10% (0.3/3.1 ≈ 0.097). A low ratio like this suggests a higher likelihood of prostate cancer, because cancer tends to shed more PSA in a bound form and less as free PSA. In contrast, benign prostatic hyperplasia usually yields a higher proportion of free PSA, leading to a higher ratio. So, even though the total PSA is in a gray-zone range, the markedly low free PSA fraction points to increased cancer risk rather than a benign process. This pattern would typically prompt further evaluation, such as discussion of a biopsy, taking into account other risk factors and clinical context.

The key idea is that the relationship between free PSA and total PSA helps distinguish cancer from benign conditions when PSA is elevated. Total PSA is 3.1 ng/mL, and free PSA is 0.3 ng/mL, giving a free-to-total PSA ratio of about 10% (0.3/3.1 ≈ 0.097). A low ratio like this suggests a higher likelihood of prostate cancer, because cancer tends to shed more PSA in a bound form and less as free PSA. In contrast, benign prostatic hyperplasia usually yields a higher proportion of free PSA, leading to a higher ratio. So, even though the total PSA is in a gray-zone range, the markedly low free PSA fraction points to increased cancer risk rather than a benign process. This pattern would typically prompt further evaluation, such as discussion of a biopsy, taking into account other risk factors and clinical context.