PROSTATE-SPECIFIC ANTIGEN AND PROGNOSIS IN PATIENTS WITH METASTATIC PROSTATE-CANCER - A MULTIVARIABLE ANALYSIS OF PROSTATE-CANCER MORTALITY

Objective To analyse the prognostic significance of pre-and post-treat ment serum prostate-specific antigen (PSA) levels, together with a var iety of other factors, in a multivariable analysis of survival in men with stage D2 prostate cancer. Patients and methods Cox's proportional hazards model was used to compare survival in 134 men with stage D2 m etastatic prostate cancer followed prospectively over a 4 year period, using both univariable and multivariable models. The influence of the following factors on survival was analysed: pre- and post-treatment P SA (both absolute and percentage values), age, treatment, testosterone , pre- and post-treatment alkaline phosphatase (absolute and percentag e values), acid phosphatase, haemoglobin, symptom score and performanc e status and extent of disease on bone scan. Results Pre-treatment PSA levels did not significantly influence survival. Similarly, a low abs olute posttreatment PSA level at 3 months after the start of treatment conferred no survival advantage relative to patients with a high PSA level at this time. A posttreatment percentage PSA of < 10% at 2, 3 an d 6 months after commencement of treatment was associated with prolong ed survival. Low pre-treatment alkaline phosphatase (less than the upp er limit of normal) and high pre-treatment testosterone levels (10 nmo l/L) were similarly associated with prolonged survival. Conclusions Th e strong influence of post-treatment percentage PSA on survival in pat ients with stage D2 prostate cancer suggests that the percentage chang e in bulk of metastatic deposits is more important in determining surv ival than the absolute volume of tumour. Pre-treatment alkaline phosph atase seems to be a better indicator of tumour activity than pretreatm ent PSA. These findings have important implications for the design and analysis of clinical trials of new therapies in men with stage D2 pro state cancer and for the future selection of alternative treatments fo r patients with this stage of the disease.