Long-term outcomes after treatment with external beam radiation therapy and palladium 103 for patients with higher risk prostate carcinoma: influence of prostatic acid phosphatase.
BACKGROUND
The objective of this study was to define the long-term prognostic significance of prostatic acid phosphatase (PAP) levels in patients with higher risk, early-stage prostate carcinoma.


METHODS
One hundred sixty-one consecutive patients with Stage T1-T3 prostate carcinoma (according to the 1992 criteria of the American Joint Committee on Cancer) were treated from 1992 through 1996. Each patient had a Gleason score > or = 7 and/or a prostate specific antigen (PSA) level > 10 ng/mL. The original biopsy slides for 130 of 161 patients were retrieved and rereviewed by a single pathologist (L.T.). Enzymatic PAP measurements were determined using a standard method. Values up to 2.5 Units were considered normal. Patients received 41 grays (Gy) of external beam radiation therapy to a limited pelvic field followed 4 weeks later by a palladium 103 (Pd-103) boost using transrectal ultrasound and fluoroscopic guidance as described previously. The prescribed minimum Pd-103 dose to the prostate was 80 Gy (pre-National Institute of Standards and Technology [NIST]-99). Freedom from biochemical failure was defined as a serum PSA level < or =0.2 ng/mL at last follow-up.


RESULTS
There was little correlation between pretreatment PSA levels, Gleason scores, and PAP measurements. Thirty-eight patients developed biochemical failure. The overall actuarial freedom from biochemical progression at 10 years is 79%, with 118 patients followed for > 5 years. In a multivariate Cox proportional hazards analysis that considered each factor as a continuous variable, the strongest predictor of failure was PAP (P = 0.0001), followed by Gleason score (P = 0.13), and PSA (P = 0.04). PAP was especially helpful in stratifying patients with pretreatment PSA levels between 4 ng/mL and 20 ng/mL, for whom the prognosis does not different when they are subdivided into PSA categories. When the PAP subgroup analysis was limited to this relatively favorable group, there was a wide range of prognoses.


CONCLUSIONS
The biochemical cure rate was remarkably high among the 161 patients evaluated. The fact that the PAP was the strongest predictor of long-term biochemical failure in patients with otherwise higher risk features reported here suggests that it may be a more accurate indicator of micrometastatic disease compared with the Gleason score and the PSA level. This report adds to the rationale for reintroducing PAP measurement into general practice.
Dattoli
Michael
M
Dattoli Cancer Center and Brachytherapy Research Institute, Sarasota, Florida 34237, USA.
Wallner
Kent
K
True
Lawrence
L
Cash
Jennifer
J
Sorace
Richard
R
D000135:Acid Phosphatase; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D001918:Brachytherapy; D002277:Carcinoma / Q000201:enzymology / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010165:Palladium / Q000627:therapeutic use*; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000473:pathology / Q000532:radiotherapy*; D017027:Protein Tyrosine Phosphatases / Q000032:analysis*; D011868:Radioisotopes / Q000627:therapeutic use*; D013997:Time Factors; D016896:Treatment Outcome
D014408:Biomarkers, Tumor; D011868:Radioisotopes; D010165:Palladium; D000135:Acid Phosphatase; C428439:prostatic acid phosphatase; D017027:Protein Tyrosine Phosphatases