Definitions of "Cure" After Low-Dose-Rate Brachytherapy in Low- and Intermediate-Risk Prostate Cancer: Phoenix or Surgical?

Purpose: The aim of this study was to compare a surgical with a Phoenix-derived definition of cure at 4 years after treatment by 125J low-dose-rate brachytherapy (LDR-BT) in patients with low-and intermediate-risk prostate cancer. Methods and Materials: A total of 427 evaluable men with low-risk (62.8%) and intermediate-risk (37.2%) prostate cancer were treated with LDR-BT (160 Gy). Cure was defined at 4 years either as not having experienced a biochemical recurrence by the Phoenix definition, or by a surgical definition, using a posttreatment prostate-specific antigen of & LE;0.2 ng/mL. Biochemical recurrence-free survival (BRFS), metastasis-free survival (MFS), and cancer-specific survival were calculated at 5 and 10 years using the Kaplan-Meier method. Standard diagnostic test evaluations were used to compare both definitions with regard to later metastatic failure or cancer -specific death. Results: At 48 months, 427 patients were evaluable with a Phoenix-defined and 327 with a surgical-defined cure. At 5 and 10 years BRFS was 97.4% and 89% and MFS was 99.5% and 96.3% in the Phoenix-defined cure cohort, and BRFS was 98.2% and 92.7% and MFS was 100% and 99.4% in the surgical-defined cure cohort. Specificity for cure was 100% for both definitions. Sensitivity was 97.4% for the Phoenix and 96.3% for the surgical definition. The positive predictive value was 100% for both, whereas the negative predictive value was 29% for the Phoenix and 7.7% for the surgical definition. Accuracies of a correct prediction of cure were 94.8% and 96.3% for the Phoenix and the surgical definition, respectively. Conclusions: Both definitions are useful for a reliable assessment of cure after LDR-BT in patients with low-risk and intermediate-risk prostate cancer. Cured patients might follow a less stringent follow-up schedule from 4 years onward, whereas patients not achieving cure at 4 years should be monitored for an extended time. (C) 2022 The Author(s). Published by Elsevier Inc. on behalf of American Society for Radiation Oncology.