Is MRI-based Week Three Post-implant Dosimetry Necessary following LDR Prostate Brachytherapy?

Abstract

Materials/Methods: Data were obtained from the Surveillance, Epidemiology, and End Results Program (SEER) for the years 2004-2005. Men with adenocarcinoma of the prostate who had complete clinical TNM staging information were included, and descriptive statistics were performed. Results: A total of 59,351 subjects were identified, of whom 14,842 had a prostatectomy with complete pathologic staging. ClinicalT-stagewasT1cin65.3%,T2cin15.8%,T2ain7.3%,T2bin2.9%,andwasT3orgreaterin3.6%.PathologicT-stagewasT2c in 63%, T2a in 14.6%, T3a in 10.7%, T3b in 6.6%, T2b in 2.7% and T4 in 2.3%. No subjects had a pathologic T-downstaging. Of 14,842 patients with pathologic nodal data, 2.3% had positive nodes, the majority falling into the high risk group. Only 2.9% of clinically orpathologicallystagedpatientshad metastatic diseaseat presentation. Therewere 12,441subjectswith AJCCstageI-III diseasewithcompleteclinicalandpathologicTNMstaging,Gleasonsum,andPSAdata.Whenstratifiedintolow,intermediateand high risk groups based on the D’Amico criteria, 75.7% of clinically staged low risk patients were up-risk-stratified to the high-risk group after prostatectomy. Amongst intermediate risk group patients, 84.6% were up-risk-stratified. Only 0.9% of patients were down-risk-stratified. Utilizing the Roach formula for subjects who had pathologic nodal evaluation, those with a predicted likelihood of positive nodes of 0-5%, 5.1-10%, 10.1%-15%, and .15% were found to have 0.2%, 0.4%, 1.1%, and 6.5% incidence of positive nodes respectively. Conclusions: Complete pathologic staging results in a higher risk-stratification than that predicted by clinical criteria in the majority of patients. This finding can confound the interpretation of outcomes in matched cohort studies comparing surgical to non-surgical treatments for prostate cancer. Nodal positivity is uncommon in men with prostate cancer at diagnosis. Predictive nomograms based on older surgical series significantly overestimate the actual risk of node positive disease in the current era.