ASTRO 2021: Elective Nodal Irradiation with a Simultaneous Hypofractionated Integrated Prostate Boost for Localized High-Risk Prostate Cancer: Long-Term Results From a Prospective Clinical Trial

(UroToday.com) The 2021 American Society for Radiation Oncology (ASTRO) Hybrid Annual Meeting included a presentation by Dr. Patrick Cheung discussing long-term results from a prospective clinical trial assessing elective nodal irradiation with a simultaneous hypofractionated integrated prostate boost for localized-high-risk prostate cancer.

Moderate hypofractionation has been extensively investigated as an alternative to conventional fractionation in localized prostate, and the ASTRO/ASCO/AUA guideline recommends moderate hypofractionation (2.4-3.4 Gy per fraction) for high-risk prostate cancer if not delivering elective pelvic nodal irradiation. Dr. Cheung asks “what if we want to deliver elective pelvic nodal irradiation with a moderate hypofractionated approach to the prostate?” The hypothesis being that elective pelvic nodal irradiation delivered with a simultaneous integrated hypofractionated prostate boost is a safe and effective method to combine these two treatment strategies.

This was a prospective phase I/II single-arm single-institutional trial conducted from 2004-2010 over which time 230 patients were enrolled. The schema for this trial is as follows:

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Daily image guidance to implanted prostate fiducial markers was undertaken and PTV around the prostate was 4 mm for the hypofractionated boost. The median follow-up for this trial was 11.2 years (IQR 8.1-12.9). There were 27.4% of patients that had cT3 disease, 66.9% had Gleason score 8-9 disease, the median PSA was 17.3 ng/mL, and 67.4% of patients had at least one high-risk feature. A summary of the baseline characteristics is as follows:

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The cumulative incidence of biochemical failure was 15% at five years, 33% at 10 years, and 35% at 13 years:

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The cumulative incidence of distant failure was 7% at five years, 17% at 10 years, and 21% at 13 years:

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Overall survival at five years was 93%, 76% at 10 years, and 62% at 13 years:

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On multivariable analysis, PSA nadir >= 0.05 was predictive of biochemical failure (HR 6.8, 95% CI 4.0-11.8) and distant metastasis (HR 7.5, 95% CI 3.9-14.5). Predictors of overall survival included PSA nadir >= 0.1 (HR 5.2, 95% CI 2.2-12.0) and duration of ADT <=12 vs >24 months (HR 2.3, 95% CI 1.3-3.9). With regards to urinary scores, the mean change from baseline was +2.2, with no statistically significant difference over time (p=0.08). Similarly, the mean change from baseline for bowel scores from baseline was -2.5, with no statistically significant difference over time (p=0.18).

Dr. Cheung concluded his presentation with the following take-home messages:

  • Long term follow-up of elective pelvic nodal irradiation (45 Gy in 25 fractions) with a simultaneous integrated moderately hypofractionated boost to the prostate (67.5 Gy in 25 fractions) plus ADT for patients with high-risk prostate cancer resulted in: effective oncologic treatment, minimal impact on patient reported GU and GI quality of life, and low rates of grade >= 3 late GI and GU toxicity
  • Based on these findings, the manuscript is now published.1

 

Presented by: Patrick Cheung, MD, FRCPC, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, Canada

Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2021 American Society for Radiation Oncology (ASTRO) Hybrid Annual Meeting, Sat, Oct 23 – Wed, Oct 27, 2021.

References:

  1. Glicksman RM, Loblaw A, Morton G, et al. Elective pelvic nodal irradiation with a simultaneous hypofractionated integrated prostate boost for localized high risk prostate cancer: Long term results from a prospective clinical trial. Radiother Oncol. 2021 Jul 26;163:21-31.

 

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