Biochemical Monitoring of Carcinoma of Prostate Treated with an LH‐RH Analogue (Zoladex)

The levels of prostatic specific antigen (PSA) and prostatic acid phosphatase (PAP), both measured by radioimmunoassay, and two cancer indices given by the ratio of serum alpha-1 acid glycoprotein to prealbumin (AGP:Palb) and alpha-1 acid glycoprotein to alpha-2 HS globulin (AGP:HS) were evaluated as markers to assess the response of prostatic cancer to treatment with Zoladex, an LH-RH agonist. A rise in PSA and PAP occurred in 8/65 patients (12%) during the initial induction phase. In metastatic disease prior to treatment none of these indices was significantly different between patients who attained a sustained response and those whose response was nil or only transient. Responders and non-responders could, however, be distinguished by the levels of various analytes after treatment. At 6 months the median PSA in those who responded was 2.5 ng/ml compared with 51.5 ng/ml in the non-responders. At 12 months the figures were 3.0 and 155 ng/ml respectively. The corresponding median PAP levels were 1.4 and 19 ng/ml at 6 months and 1.3 and 18 ng/ml at 12 months. The AGP:Palb ratio was also significantly different in these two groups at 6 and 12 months. PSA appears to be the most sensitive indicator of the response to treatment. The likelihood of obtaining a prolonged clinical response can be assessed within 6 months of the start of treatment.