Prostate carcinoma patients upstaged by imaging and treated with irradiation. An outcome-based analysis

Abstract

Background: The American Joint Committee on Cancer (AJCC) staging of prostate cancer relies upon digital rectal examination (DRE) findings, but suggests using all available information, including prostate imaging studies, prior to definitive treatment of prostate carcinoma. We have studied whether patients upstaged by imaging have a different outcome after treatment with external beam radiation therapy (RT) from those not upstaged.

Methods: The records of 499 men with clinically localized adenocarcinoma of the prostate treated with only definitive external beam irradiation from January 1986 to December 1993 were reviewed. The 348 patients with any one or a combination of the following pretreatment imaging studies were considered eligible; transrectal ultrasound (TRUS), pelvic MRI, or endorectal MRI. Patients were assigned two clinical stages: one based upon palpation criteria alone (palpation stage) and the other allowing for any upstaging by imaging abnormalities (AJCC or imaging stage). The Kaplan-Meier method was used to estimate biochemical no evidence of disease (bNED) survival where a failure was defined as a prostate specific antigen (PSA) greater than 1.5 and increasing. Differences in outcome were evaluated by the log-rank test.

Results: Overall upstaging by TRUS or MRI to any higher stage occurred in 115 of 312 palpation T1c-T2c patients (37%). These upstaged patients had an unexpected improvement in bNED survival (84% vs. 71%, P = 0.05) compared with those who were not upstaged due to the upstaged patients having a significantly greater number with a pretreatment PSA < 10 ng/mL. T1c patients were upstaged by imaging in 81% of the 94 patients. The 36-month bNED survival of palpation T1c and imaging T2 patients was similar (88% vs. 88%, P = NS), but both were significantly improved compared with the 36-month bNED survival for palpation T2 patients (88% vs. 71%, P = 0.04). There was no significant difference in 36-month bNED survival for imaging T2c (bilobar disease) patients compared with their original palpation stage disease. Upstaging to T3 occurred in 10% of palpation T1c-T2c patients. There was no difference in 36-month bNED survival for the imaging T3 patients compared with their original palpation stage (84% vs. 71%, respectively, P = 0.04). There was a significant improvement in the 36-month bNED survival for imaging T3 patients compared with palpation T3 patients (84% vs. 50% respectively, P = 0.01). Multivariate analysis demonstrated palpation stage to be a significant predictor of bNED survival (P = 0.001), while AJCC stage (including imaging) is not predictive.

Conclusions: Using the endpoint of bNED survival, upstaging by TRUS/MRI does not separate prostate cancer patients treated with RT into groups with different prognoses. Upon multivariate analysis, palpation stage alone, not AJCC stage including imaging upstaging, is a significant predictor of bNED survival.