Correlation of survival with quantitative tissue staining of prostate specific acid phosphatase in patients with prostate carcinoma by using microscopic image analysis: a preliminary report of correlative studies on RTOG protocols 75-06, 77-06, and 83-07.

PURPOSE

We have previously shown that the intensity (graded semiquantitatively as 1-4+) of tissue prostate-specific acid phosphatase (PSAP) staining determined immunocytochemically in a cohort of prostate carcinoma patients from Radiation Therapy Oncology Group Protocols (RTOG) protocols 75-06 and 77-06 correlated with survival. The extent of this staining was heterogeneous and was estimated. The extent of staining was not found to be significantly associated with survival. We undertook the present quantitative study to see if the improved precision and reliability of measurement of the intensity and extent of prostate specific acid phosphatase staining would confirm and extend our previous observations.

METHODS AND MATERIALS

Patient cohorts representative of the entire group were obtained from RTOG 75-06 plus 77-06 and 83-07. The RTOG 77-06 plus 75-06 patients (No-Hormone population) did not receive preradiation hormonal therapy. RTOG 83-07 patients (Prehormone population) received one of two types of preradiation chemical androgen ablation. In this study, histologic slides of tumors were immunocytochemically stained for PSAP by the peroxidase-antiperoxidase (PAP) technique using diaminobenezidene (DAB) as a substrate and hematoxylin as a nuclear counterstain. The intensity and extent of immunocytochemical PSAP staining (IPSAP stain) was quantified using our dual wavelength and batch mode image process technique.

RESULTS

Our study of 151 cases confirmed that overall survival of patients in both populations was positively correlated with the intensity and extent of IPSAP stain. Results of the two studies were similar. The statistical significance of the relationship of both extent and intensity was greater in the cohort from protocol 83-07, which was the patient group receiving pretreatment with hormones. In a Cox multiple regression analysis including clinical stage, Gleason and M. D. Anderson grades, and the cohort of patients (Prehormone or No-Hormone group) as covariables, both the intensity and extent of the IPSAP stain significantly correlated with survival along with M. D. Anderson grade of the tumor.

CONCLUSION

Quantitative image analysis of the IPSAP stain predicts survival in patients treated with external beam radiotherapy with and without prior hormonal therapy.