Multicenter Trial of Stereotactic Body Radiation Therapy for Low- and Intermediate-Risk Prostate Cancer: Survival and Toxicity Endpoints

Int J Radiat Oncol Biol Phys. 2018 Oct 1;102(2):296-303. doi: 10.1016/j.ijrobp.2018.05.040. Epub 2018 Jun 1.

Abstract

Purpose: The radiobiology of prostate cancer may favor the extreme hypofractionation inherent in stereotactic body radiation therapy (SBRT); however, data from a large multicenter study are lacking. We therefore examined the hypothesis that dose-escalated SBRT can be safely administered across multiple institutions, with favorable 5-year disease-free survival (DFS) rates compared with historical controls.

Methods and materials: Twenty-one centers enrolled 309 patients with prostate adenocarcinoma: 172 with low-risk (LR) and 137 with intermediate-risk (IR) disease. All were treated with a non-coplanar robotic SBRT platform using real-time tracking of implanted fiducials. The prostate was prescribed 40 Gy in 5 fractions of 8 Gy. We assessed toxicities using Common Terminology Criteria for Adverse Events (CTCAE) version 3 and biochemical failure using the "nadir + 2" definition. The study population yielded 90% power to identify excessive (>10%) rates of grade ≥3 genitourinary (GU) or gastrointestinal toxicities and, in the LR group, 80% power to show superiority in DFS over a 93% historical comparison rate.

Results: At a median follow-up of 61 months, 2 LR patients (1.2%) and 2 IR patients (1.5%) experienced grade 3 GU toxicities, far below the 10% toxicity rate deemed excessive (upper limits of 95% confidence interval, 3.5% and 4.3%, respectively). No grade 4 or 5 toxicities occurred. All grade 3 toxicities were GU, occurring 11 to 51 months after treatment. For the entire group, the actuarial 5-year overall survival rate was 95.6% and the DFS rate was 97.1%. The 5-year DFS rate was 97.3% for LR patients (superior to the 93% DFS rate for historical controls; P = .0008; lower limit of 95% confidence interval, 94.6%) and 97.1% for IR patients.

Conclusions: Dose-escalated prostate SBRT was administered with minimal toxicity in this multi-institutional study. Relapse rates compared favorably with historical controls. SBRT is a suitable option for LR and IR prostate cancer.

Trial registration: ClinicalTrials.gov NCT00643994.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / blood
  • Adenocarcinoma / mortality*
  • Adenocarcinoma / pathology
  • Adenocarcinoma / radiotherapy*
  • Adult
  • Aged
  • Aged, 80 and over
  • Disease-Free Survival
  • Humans
  • Male
  • Middle Aged
  • Prostate-Specific Antigen / blood
  • Prostatic Neoplasms / blood
  • Prostatic Neoplasms / mortality*
  • Prostatic Neoplasms / pathology
  • Prostatic Neoplasms / radiotherapy*
  • Radiosurgery / adverse effects*
  • Radiosurgery / methods
  • Radiosurgery / mortality*
  • Radiotherapy Dosage
  • Robotic Surgical Procedures / adverse effects
  • Robotic Surgical Procedures / methods
  • Robotic Surgical Procedures / mortality

Substances

  • Prostate-Specific Antigen

Associated data

  • ClinicalTrials.gov/NCT00643994