Can PSA levels guide how biopsies should be obtained?

This study evaluated the performance of magnetic resonance imaging/ultrasound targeted biopsy versus transrectal ultrasound (TRUS) biopsy alone in patients with different prostate specific antigen levels. 

A new magnetic resonance imaging (MRI: uses a magnetic field and pulses of radio wave energy to take pictures of inside the body) technique, combined with transrectal ultrasound (TRUS) imaging, can be used to find the location of prostate tumors. TRUS imaging involves an ultrasound probe being inserted into the back passage to allow imaging of the prostate gland and biopsy sampling. Firstly, MRI is used to make pictures of the prostate and any visible tumors. These images are then used to target tumors during TRUS biopsy selection.

This method improves the chances of finding tumors and allows for improved diagnosis of cancer grade.  However, it is a costly and time consuming procedure. To improve efficiency it would be good to determine if certain patients would benefit more from this new method compared to the use of TRUS alone. 

This study included 1,003 men with possible prostate cancer (average age 62 years). Prostate specific antigen (PSA: a protein produced by the prostate, with levels elevated in patients with prostate cancer) levels were measured in blood samples from each patient before imaging was carried out. Patients were then grouped based on these PSA levels: 81 patients in group 1 (0-2.5 ng/ml of PSA); 131 patients in group 2 (2.5-4 ng/ml of PSA); 513 patients in group 3 (4-10 ng/ml of PSA); and 278 patients in group 4 (greater than 10 ng/ml of PSA). All patients were screened for cancer using both the MRI guided biopsy method and the commonly used TRUS biopsy method. Results for both methods were compared.

Overall, cancer was detected in 56.2% of the patients. There was no difference in the rate of cancer detection between the two methods. However, the authors found that in patients with PSA levels greater than 5.2 ng/ml, MRI guided biopsy was better at grading the cancer severity.

In patients with PSA levels below 5.2 ng/ml there was no benefit to using MRI guided biopsy selection. However, in patients with higher PSA levels MRI guided biopsies were better at grading the cancer severity.