Serum free/total prostatic-specific antigen in prostate cancer patients treated with LH-RH agonists

This study is based on promising results using the ratio of free/ total (F/T) prostatic-specific antigen (PSA) for discrimination between benign prostatic hypertrophy and prostate cancer. We tried to determine the value of F/T PSA in different clinical situations at a certain time point during follow-up of luteinizing-hormone-releasing hormone (LH-RH) agonist treatment and to correlate it to T-PSA.

182 patients followed-up for different periods in the last 3 years were routinely monitored for serum T-PSA. During the last 11 months, F-PSA was also measured together with T-PSA, and the ratio of F/T PSA was calculated. In 26 patients, the ratio of F/T PSA was monitored sequentially in several samples.

Although 5 patterns of clinical response to LH-RH agonists were identified according to previous T-PSA, the F/T ratio could significantly (p < 0.05) discriminate between patients responding to treatment in contrast to patients escaping, fluctuating or not responding to hormonal ablation. Those patients responding to hormones showed a higher F/T PSA ratio (36.5 +/- 33.1%) compared to the nonresponding group (12.0 +/- 10.1%).

During individual follow-ups, the pattern of response to LH-RH treatment is reflected by the F/T PSA ratio: while successful treatment causes an F/T PSA increase, relapse is accompanied by a decrease in this ratio. However, the changes in the F/T PSA ratio did not precede the indicative changes in T-PSA. It seems that increased values of F/T PSA ratios are intrinsic features of 'benign' prostatic disease, and the molecular events resulting in different PSA molecules in various clinical situations have to be elucidated.