ASTRO 2021: Elective Nodal Ultra Hypofractionated Radiation for Prostate Cancer: Safety and Efficacy from Four Prospective Trials

(UroToday.com) In a GU session at the American Society for Radiation Oncology (ASTRO) Annual Congress, Dr. Glicksman presented pooled results from four prospective trials evaluating the role of elective nodal ultra hypofractionated radiation in treatment of patients with prostate cancer.

Dr. Glicksman began by highlighting that the use of stereotactic body radiotherapy (SBRT) for the treatment of patients with prostate cancer is increasing. Independent of fractionation approach, the role of elective nodal irradiation (ENI) is somewhat controversial though it is commonly employed in patients with high-risk disease. However, there are limited data regarding the safety of ENI using an ultra hypofractionated radiation (UHRT) regime.

To address this, the authors used data from four prospective, phase II trials of ENI using UHRT which included patients with unfavourable intermediate and high risk prostate cancer. Radiotherapy was administered to the pelvic lymph nodes with nodal CTV contouring according to the 2009 RTOG atlas and a PTV of 6mm. The nodal CTV dose was 25 Gy in 5 fractions whereas the PTV was 23.25 Gy in 5 fractions.

Among the four included trials, different primary therapy regimes were employed including hypofractionated external beam radiotherapy in 5 fractions with or without MR boost or HDR boost.

In each study, the primary outcome was acute toxicity while secondary endpoints included late toxicity, patient-reported outcomes, and oncologic outcomes. Physician adjudicated toxicity was assessed using CTCAE v3 and v4.

Among 165 included patients, the median follow-up was 38 months (IQ5 11-63 months) and the majority of patients had high-risk disease. At baseline most had minimal urinary symptoms (62% with IPSS 0-9).

Grade 1 acute GI toxicity occurred in 41% of patients while grade 2 occurred in 7.5%. In terms of GU toxicity, grade 1 toxicity was seen in 31%, grade 2 in 48% and grade 3 in 3%.

Considering late toxicity, the worst late GU toxicity was grade 1 for 41%, grade 2 for 41%, and grade 3 for 1.5%.

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In terms of late GI toxicity, rates were somewhat lower with the worst late GI toxicity being grade 1 for 31% and grade 2 for 10.5% while the remainder were grade 0.

Using patient-reported EPIC scores, the authors found an increase in urinary and bowel-related scores over time, which continued to significantly increase over ongoing follow-up. However, sexual function scores significantly decreased at month 3 compared to baseline and remained significantly lower at months 6 and 12, though with an increase during follow-up.

Biochemical recurrence free survival was 98% at 3 years, 95% at 4 years and 93% at 5 years while the corresponding rates for metastasis free survival were 98%, 98%, and 94% and for overall survival were 96%, 94%, and 92%.

Dr. Glicksman therefore concluded that ENI using UHRT is associated with low rate sof GU and GI toxicity, though there is worse bowel and sexual function reported by patients in the year following treatment. Ongoing assessment of this approach in phase III trials is anticipated.

Presented by: Rachel M. Glicksman, MD, MSc, Radiation Oncology, University of Toronto


Written by: Christopher J.D. Wallis, University of Toronto, Twitter: @WallisCJD during the 2021 American Society for Radiation Oncology (ASTRO) Hybrid Annual Meeting, Sat, Oct 23 – Wed, Oct 27, 2021.

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