MEASUREMENTS OF TISSUE POLYPEPTIDE-SPECIFIC ANTIGEN AND PROSTATE-SPECIFIC ANTIGEN IN PROSTATE-CANCER PATIENTS UNDER INTERMITTENT ANDROGEN SUPPRESSION THERAPY

The present study evaluated serial serum measurements of tissue polype ptide-specific antigen (TPS) in comparison with prostate-specific anti gen (PSA) for assessment of tumour progression in patients with advanc ed prostate cancer receiving intermittent androgen suppression therapy (IAS). Twenty-three men were recruited into an IAS trial consisting o f an initial 8 months of androgen suppression, followed by cycles of t reatment cessation and resumption of therapy upon increases of PSA > 2 0 ng ml(-1) to prolong the hormone responsiveness of the tumour cells. Periods of androgen suppression resulted in reversible reduction in s erum testosterone (< 1.8 nmol I-1) and PSA (< 4 ng ml(-1)) and decreas es in tumour volume (mean reduction for first cycle 24 +/- 10%), indic ating partial growth arrest and apoptotic regression of the tumours. I n contrast to PSA values, non-specifically elevated TPS values were fo und in 8 of 23 patients. In 15 of 23 patients, TPS fell during periods of apoptotic tumour regression and increased simultaneously with test osterone and preceded the increases in PSA by 2 months during the peri od of treatment cessation. Although TPS represents a highly sensitive marker of tumour proliferation in this IAS clinical model of controlle d tumour regression and regrowth, its low specificity compared with PS A limits its usefulness to monitoring of prostate cancer patients with proven absence of non-specific elevations of this marker.