Interstitial implant alone or in combination with external beam radiation therapy for intermediate-risk prostate cancer: A survey of practice patterns in the United States

Purpose This study is aimed at understanding and defining the current patterns of care with respect to prostate brachytherapy for patients with intermediate-risk localized disease in the combined academic and community setting. Methods and materials A nomogram-based survey was developed at the Seattle Prostate Institute defining the accepted criteria for intermediate-risk prostate cancer. Patients were defined as having intermediate-risk prostate cancer if they met one of the following criteria: prostate-specific antigen (PSA) >10 ng/dL, Gleason score (GS) ≥7, or cT2b or cT2c disease. Additional potential predictive factors including perineural invasion (PNI), GS 3 + 4 vs. 4 + 3, and high-volume disease were included. Results In the absence of PNI, all of those surveyed would perform monotherapy for intermediate-risk patients, GS 7 (3 + 4) or PSA 10–20, with cT1c and <30% cores +. Up to 80% would perform monotherapy for patients with cT1c, GS 7 (4 + 3), and <30% cores +. Eighty to 90% of physicians would perform an implant alone with cT2a and either a PSA of 10–20 or GS of 7 (3 + 4) and <30% cores +. Fifty to 60% of those surveyed stated that they would treat a patient with cT2b disease, GS 7 (3 + 4), or PSA 11–20, with less than two-thirds of the biopsy cores positive in the absence of PNI. Conclusions This Patterns of Care (POC) study reveals that certain subsets of intermediate-risk localized prostate cancer patients are considered appropriate candidates for an interstitial implant alone.