Comparing prostate specific antigen outcomes after different types of radiotherapy management of clinically localized prostate cancer highlights the importance of controlling for established prognostic factors.
OBJECTIVE
We evaluated the impact that the composition of prognostic factors in a patient cohort may have on prostate specific antigen (PSA) outcome following external beam radiation therapy for clinically localized prostate cancer.


METHODS
The distribution of PSA, biopsy Gleason score and American Joint Committee on Cancer (AJCC) T stage in men with prostate cancer treated with interstitial plus external beam radiation therapy was used to select a matched cohort who underwent 3-dimensional (D) conformal external beam radiation therapy. We compared PSA outcomes after 3-D conformal external beam radiation therapy in the overall and matched cohorts of 766 and 570 patients, respectively.


RESULTS
Men treated with interstitial plus external beam radiation therapy had a significantly lower rate of PSA greater than 10 to 20 (p = 0. 02) and greater than 20 ng./ml. (p <0.0001), biopsy Gleason score 7 (p = 0.02) and 8 to 10 (p <0.0001), and AJCC stage T2c disease (p <0. 0001). Likewise, these men also had a significantly higher rate of PSA greater than 4 to 10 ng./ml. (p <0.0001), biopsy Gleason score 5 to 6 (p = 0.0001) and AJCC stage T1 disease (p <0.0001) than those who underwent 3-D conformal external beam radiation therapy. The 5-year estimate of PSA failure-free survival after 3-D conformal external beam radiation therapy was 45% versus 67% (p = 0.0007) for all 766 consecutively treated patients and the matched cohort of 570, respectively.


CONCLUSIONS
The composition of prognostic factors in a patient cohort may impact PSA outcome. Therefore, controlling for established prognostic factors is essential when comparing PSA outcome after different forms of radiotherapy for adenocarcinoma of the prostate.
D'Amico
A V
AV
Departments of Radiation Oncology and Urology, Brigham and Women's Hospital, Dana Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA.
Schultz
D
D
Schneider
L
L
Hurwitz
M
M
Kantoff
P W
PW
Richie
J P
JP
D000230:Adenocarcinoma / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal
D017430:Prostate-Specific Antigen