Comparison of outcome endpoints in intermediate- and high-risk prostate cancer after combined-modality radiotherapy

Brachytherapy. Jan-Feb 2020;19(1):24-32. doi: 10.1016/j.brachy.2019.09.001. Epub 2019 Oct 16.

Abstract

Purpose: To compare a standard radio-oncological and a surgical biochemical failure definition after combined-modality radiation therapy (CRT) in men with intermediate- and high-risk prostate cancer.

Methods: 425 men were treated with external beam radiotherapy (59.4 Gy, 33 fractions) and 125J seed-brachytherapy (S-BT, 100 Gy). Biochemical recurrence (BR) was defined either as radio-oncologic (rBR), using a +2 ng/mL prostate-specific antigen (PSA) increase above a nadir value, or as surgical (sBR), using a 2-year posttreatment PSA of ≥0.2 ng/mL. Biochemical recurrence-free, metastasis-free, cancer-specific, and overall survival were calculated at 5 and 10 years using the Kaplan-Meier method. Standard validation tests were used to compare both thresholds.

Results: After a median of 7 years, overall recurrence rates were 10.4% and 31.5% for rBR and sBR definitions, respectively. Both failure definitions proved sensitive for the prediction of metastases and cancer-specific death, whereas the rBR definition was significantly more specific. The accuracies of a correct prediction of metastases and death of prostate cancer were 73.1% vs. 96.2% and 72.2% vs. 92.9% for sBR vs. rBR, respectively. The inferior validity results of the sBR definition were attributable to a PSA-bounce phenomenon occurring in 56% of patients with sBR. Still, using the less suitable sBR definition, the results of CRT compared favorably to BRFS rates of surgical interventions.

Conclusion: After CRT, the radio-oncological (aka Phoenix) failure definition is more reliable than a fixed surgical endpoint. Exclusively in high-risk patients, sBR offers a direct comparison across surgical and nonsurgical treatment options at 5 and 10 years.

Keywords: Biochemical recurrence; LDR-Brachytherapy; Outcome research; PSA bounce; Prostate cancer; Radiotherapy.

Publication types

  • Comparative Study

MeSH terms

  • Aged
  • Aged, 80 and over
  • Brachytherapy*
  • Dose Fractionation, Radiation
  • Endpoint Determination
  • Humans
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • Neoplasm Metastasis
  • Neoplasm Recurrence, Local / blood*
  • Predictive Value of Tests
  • Prostate-Specific Antigen / blood*
  • Prostatic Neoplasms / blood
  • Prostatic Neoplasms / pathology
  • Prostatic Neoplasms / radiotherapy*
  • Prostatic Neoplasms / surgery*
  • Risk Factors
  • Survival Rate

Substances

  • Prostate-Specific Antigen