ESTRO 2022

Session Item

Monday

May 09

10:30 - 11:30

Room D4

Pelvic malignancies

Co-Chair: , Belgium;

Chair: Simon KB Spohn, Germany

Session Code: 3200

Session Type: Proffered Papers

Track: Clinical

10:50 - 11:00

Genitourinary hrQoL following Urethral sparing prostate SBRT compared with virtual HDR boost.

Matthew Richardson, Australia

Presentation Number: OC-0765

Abstract

Abstract Title:

Genitourinary hrQoL following Urethral sparing prostate SBRT compared with virtual HDR boost.

Authors:

Matthew Richardson¹, Mark Sidhom^2,3, Paul Keal⁴, Joseph Bucci^5,3, Sarah Gallagher¹, Peter Greer^1,6, Amy Hayden⁷, Andrew Kneebone^8,9, David Pryor^10,11, Shankar Siva¹², Jarad Martin^1,13

¹Calvary Mater Newcastle, Radiation Oncology, Newcastle, Australia; ²Liverpool Cancer Therapy Centre, Radiation Oncology, Sydney, Australia; ³University of New South Wales, Faculty of Medicine, Sydney, Australia; ⁴The University of Sydney, ACRF Image X Institute, Sydney, Australia; ⁵Cancer Care Centre, St George Hospital, Sydney, Australia; ⁶University of Newcastle, School of Mathematical and Physical Science, Newcastle, Australia; ⁷Westmead Hospital, Radiation Oncology, Sydney, Australia; ⁸The University of Sydney, Faculty of Medicine and Health, Sydney, Australia; ⁹Royal North Shore Hospital, Radiation Oncology, Sydney, Australia; ¹⁰Princess Alexandria Hospital, Radiation Oncology, Brisbane, Australia; ¹¹School of Chemistry and Physics, Queensland University of Technology, Woolloongabba, Australia; ¹²Peter MacCallum Cancer Centre, Division of Radiation Oncology and Cancer Imaging, Melbourne, Australia; ¹³University of Newcastle, School of Medicine and Public Health, Newcastle, Australia

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Purpose or Objective

Urinary symptoms after prostate radiotherapy have a measurable impact on patient quality of life. Limiting dose to the prostatic urethra is an emerging technique for prostate SBRT. We present EPIC-26 GU health related quality of life (hrQoL) outcomes 3 years post urethral sparing SBRT (US-SBRT), comparing a 5 fraction SBRT approach with an SBRT + EBRT boost alternative.

Material and Methods

We compared prospective data from two multicentre, phase 2 clinical trials of US-SBRT. The SPARK trial (ACTRN12615000335594) prescribed 36.25 Gy/5fx to the prostate (SBRT). The PROMETHEUS trial (ACTRN12615000223538) utilised an SBRT boost (19-20 Gy/2fx) combined with fractionated EBRT (46 Gy/23fx or 36 Gy/12fx). The biological equivalent dose (BED) for urethral toxicity (α/β=3) for the SBRT cohort was 123.9 Gy, and 155.8–171.2 Gy for the SBRT+EBRT cohort.
A urethra PRV was defined as a 1mm radial margin from urinary catheter, or estimated from MRI +3mm radially. Urethra PRV dose limits were applied such that for SBRT and SBRT+EBRT Dmax was 0.1cc ≤107% and <110% respectively, and V105% TD <5% in both cohorts.
Patients completed an EPIC-26 questionnaire at baseline and then repeated up to 36 months post RT. Comparisons between cohorts were performed. We recorded any minimal clinically important change (MCIC) of >0.5 standard deviation decrease from baseline score.

Results

EPIC scoring was completed at baseline by 45 SBRT patients (96% intermediate, 4% low-risk) with a median age of 69 (range 57-81), and 160 SBRT + EBRT patients (76% intermediate, 24% high-risk) with a median age of 70 years (range 53–81).
Independent two-tailed t-tests revealed statistically inferior urinary incontinence in the SBRT+EBRT cohort at baseline (p=.04) that continued across all time points. For irritative/obstructive outcomes, significant differences were identified at 12 and 36 months (87.2 v 79.8 and 94.2 v 86.5, both p=0.01) in favour of the SBRT cohort (Fig 1).

Figure 1. US-SBRT 3 year EPIC-26 mean urinary domain scores with 95% CI.

Chi-Square test was performed to compare the proportion of patients reporting MCIC between regimens (Table 1). While numerical differences were noted in favour of the SBRT group at 12 and 36 months, no statistically significant differences in MCIC reporting was observed (p>.05).

Conclusion

Over 3 years, SBRT+EBRT may have a larger impact on GU hrQoL than SBRT alone due to a higher BED. It is unknown whether the higher BED will also translate to improved disease control. These two regimens are currently being prospectively compared in the TROG 18.01 NINJA randomized clinical trial (ACTRN12618001806257).