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.