Prostate-specific antigen for pretreatment prediction and posttreatment evaluation of outcome after definitive irradiation for prostate cancer.

PURPOSE

This study was undertaken to assess the predictive value of pretreatment prostate-specific antigen (PSA) and the difference between clinical and PSA disease-free status in patients with long-term follow-up after irradiation for prostatic carcinoma. Comparison of the distribution of prognostic factors between surgical and radiation series was also made.

METHODS AND MATERIALS

From 1975-1989, 652 patients with clinical Stage A2-C prostatic adenocarcinoma were definitively irradiated using external beam therapy. One hundred and fifty patients with banked serum and up to 14 years follow-up have pretreatment PSA levels and 355 patients with up to 17 years follow-up have posttreatment values. Treatment failure was analyzed by tumor stage, grade, and four pretreatment PSA categories. Disease-progression was evaluated by clinical and biochemical (PSA) endpoints. Prognostic factors were compared to two surgical series.

RESULTS

A significant difference was seen in clinical and PSA disease-free (PSA < or = 4.0 ng/ml) status based on tumor grade, stage, and pretreatment PSA category. Although the expected clinical outcome has been well-documented previously, results based on posttreatment PSA levels show 5-year disease-free survivals reduced by 10-16% and 10-year survivals lessened by 15-39% depending upon the particular tumor grade and stage. The earlier stage, lower grade tumors showed the largest difference between clinical and biochemical recurrence rates at the longest interval from treatment. Even more notable were the differences in the clinical and PSA disease-free rates based on the pretreatment PSA level. Comparing the irradiated patients to two surgical series showed that the former had a larger percentage of more advanced stage tumors with more unfavorable PSA levels as compared to prostatectomy patients.

CONCLUSION

With long-term follow-up, the pretreatment PSA level continues to be a powerful predictor of clinical and biochemical outcome in patients irradiated for apparently localized prostate cancer. Differences between clinical and PSA outcome can be considerable, but oftentimes clinically insignificant. The distribution of prognostic factors between radiation and prostatectomy series seems to favor the latter.