The role of prostatic acid phosphatase in the radiotherapeutic management of adenocarcinoma of the prostate

Abstract

Between 1965 and 1984, 472 patients treated with external beam radiation therapy (EBRT) for adenocarcinoma of the prostate had pretreatment and follow-up serum prostatic acid phosphatase (PAP) measurements performed by the Roy method. All patients were clinically staged (46 A2, 67 B, and 359 C), and none had hormonal manipulation prior to relapse. Four hundred and twenty-five had pretreatment PAP values in the normal range (0.00 0.80 mIU/ml) and had an actuarial 5-year disease-free survival (DFS) of 67% (A 89%, B 93%, and C 59%). Forty-seven patients had elevated pretreatment PAP values. Three of these patients ha have remained disease free. ?l A3 or B disease, and all The remaining 44 patients were in Stage C and had a 5-year D S of 38%. This was significantly worse than the 59% DFS observed in the normal-PAP Stage C group (p 0.4 but <0.8 (P <O.Ol). In Stage C, tumor grade was found to be correlated with initial PAP values so that the higher the grade, the higher the PAP value and the greater was the incidence of elevated PAP values. Of patients with M. D. Anderson grade 4 lesions 8/33 (24%) had elevated PAP values as compared with only 6/89 (7%) elevated PAP values in patients with M. D. Anderson grade 1 tumors (p <O.OZ). Similarly a PAP <0.4 was found in 55/89 (62%) patients with grade 1 lesions while only lo/33 (30%) patients with grade 4 lesions had such low PAP values (p <O.Ol). When corrected for grade, the prognostic significance of low-normal PAP versus high-normal PAP was lost. However, an elevated PAP value was an independent adverse prognostic factor for patients with intermediate (grades 2-3) or high grade (grade 4) tumors. In grades 2 and 3, patients with elevated PAP values had a 5-year DFS of 29% compared with 57% for those with normal values (p <0.05). Patients with grade 4 tumors and elevated PAP values had a 5-year DFS of 13% versus 28% for patients with normal range PAP (p = N.S. due to small patient numbers). The role of post-treatment follow-up PAP measurements was also investigated. Following EBRT mean PAP values decreased significantly within 1 to 3 months. This was true for patients with normal pretreatment values as well as for patients with elevated initial values. For patients with initially normal PAP, the fall in PAP after treatment was of no prognostic significance. For the group of 47 patients with elevated pretreatment PAP, the initial mean PAP was 2.34 and the mean at 1 to 3 months was 0.64 (p <O.Ol). Of these 47 patients, 35 (74%) achieved normal values within 1 to 9 months after treatment and 9 (19%) did not. Of the 35 patients whose PAP normalized, 18 (51%) subsequently relapsed; of the 9 patients whose PAP did not decrease to normal range, 8 (89%) relapsed (p = 0.04). However, the 51% relapse rate of the group whose values normalized was significantly higher than the 33% relapse rate of patients who started with normal PAP (p = 0.04). We conclude that (1) the incidence of elevated PAP correlates with stage; (2) PAP has no prognostic significance in Stage A2 and B; (3) Stage C patients with higher grade tumors are more likely to have high-normal or elevated PAP; (4) even when corrected for grade elevated PAP in Stage C is an adverse factor; and (5) PAP values tend to fall after EBRT and persistent elevation post-EBRT is an especially adverse factor.