Main Session
Sep
30
PQA 07 - Genitourinary Cancer, Patient Safety, Nursing/Supportive Care
3311 - Evaluating the Criteria for Cure after Low-Dose-Rate Brachytherapy for Prostate Cancer
Presenter(s)
Kenta Onishi, MD, PhD - Nara Medical University, Kashihara, Nara
K. Onishi1, T. Nakahama1, Y. Nakai1, A. Tachibana1, N. Nishimura1, M. Tomizawa1, Y. Morizawa1, S. Hori1, D. Gotoh1, M. Miyake1, K. Yamaki2, I. Asakawa2, F. Isohashi2, K. Fujimoto1, and N. Tanaka II1,3; 1Department of Urology, Nara Medical University, Kashihara, Japan, 2Department of Radiation Oncology, Nara Medical University, Kashihara, Japan, 3Department of Prostate Brachytherapy, Nara Medical University, Kashihara, Japan
Purpose/Objective(s):
The Phoenix definition is generally used as the definition of recurrence after definitive radiation therapy for prostate cancer, while there is no criteria for cure. In this study, we aimed to investigate the factors associated with late recurrence of prostate cancer after low-dose-rate brachytherapy (LDR-BT) using machine learning.Materials/Methods:
We included 1419 patients who underwent LDR-BT for prostate cancer at our institution from August 2004 to November 2019. Of 1419 patients, 52 patients (3.7%) experienced recurrences within 5 years after treatment and 1123 patients did not experience recurrences for up to 5 years after treatment and were available for follow-up for more than 5 years. R statistical software was used for analyses of recurrence factors using random survival forests.Results:
The median age at LDR-BT was 70 years (interquartile range (IQR): 65–74), and the median initial PSA value was 7.04 (IQR: 5.26–10.34) ng/mL. According to the National Comprehensive Cancer Network (NCCN) risk classification (version 2.2019) Patients were classified as very low risk (n=28 (2.5%)), low risk (n=270 (24%)), favorable intermediate risk (n=309 (55.3%)), unfavorable intermediate risk (n=297 (26.4%)), high risk (n=191 (17%)), and very high risk (28 (2.5%)). Overall, 671 patients (59.8%) received LDR-BT alone, whereas 452 (40.2%) also received external beam radiation therapy. Neoadjuvant androgen deprivation therapy (ADT) was administered to 552 patients (49.2%) and adjuvant ADT was administered to 99 patients (8.8%). Median follow-up period was 108 (IQR: 83–120) months. Notably, 48 patients (4.3%) experienced relapse during the observation period, and the 10-year biochemical recurrence-free rate was 96.1%. The Brier score of the prediction model for late recurrence was 0.06, and the C-Index was 0.98. The variable importance factors for predicting late recurrence after LDR-BT were PSA value at 5 years, PSA doubling time (PSA-DT) at 5 years, primary Gleason pattern, and NCCN risk classification. Survival decision tree analysis to obtain cutoff values for PSA at 5 years and PSA-DT at 5 years was 0.93 ng/mL and 5.3 years.Conclusion:
We demonstrated that a PSA value <0.93 ng/mL at 5 years and a PSA-DT of 5.3 years or more are predictive factors for a late recurrence-free status after LDR-BT. We believe that extending the follow-up interval for patients who are less likely to experience late recurrence may reduce patients’ burden of hospital visits and medical costs.