(UroToday.com) The 2022 ASTRO annual meeting featured a prostate cancer session, including a presentation by Emily Holt discussing the use of hyaluronic acid as rectal spacer in prostate cancer patients undergoing hypofractionated radiotherapy. The utilization of hypofractionated radiotherapy for prostate cancer can increase patient convenience while also reduce costs. Additionally, recent randomized trials have shown no inferiority in tumor control when compared with conventionally fractionated radiotherapy.1 The correlation between the volume of rectum or rectal wall irradiated and rectal toxicities has been well documented. Thus, to reduce rectal toxicity, rectal spacers such as hyaluronic acid can be placed in the perirectal space prior to radiotherapy, increasing the distance between the prostate and rectum, allowing room for radiotherapy dose to fall off. The advantages of hyaluronic acid as a rectal spacer are as follows:
- Ease of assembly
- Ability to sculpt and control the insertion without any time constraint as it does not polymerase
- Visibility on transrectal ultrasound and magnetic resonance imaging (MRI)
- Placement can be reversed with hyaluronidase
The primary objective of this observational study of a prospective data set was to report the feasibility, post-operative complications and recto-prostatic separation achieved with hyaluronic acid inserted into the perirectal fat before definitive prostate radiotherapy.
There were 79 patients with clinical stage T1-T3 prostate cancer that underwent transrectal ultrasound guided transperineal insertion of fiducial markers and hyaluronic acid into the perirectal space before volumetric arc radiotherapy between July 2020 to July 2022. Post insertion (5-7 days after) computerized tomography (CT) and MRI scans were obtained for treatment planning. Hyaluronic acid feasibility, safety and recto-prostatic separation were assessed. Recto-prostatic separation achieved by hyaluronic acid was assessed along the prostate in the sagittal plane, 5 mm below the apex, mid-gland, and 5 mm above the base. Symmetry was assessed as maintaining >= 50% separation at the mid-gland level measured 1 cm to the left and right of the sagittal midline:
The prescribed dose to the planning target volume ranged from 60-62 Gy in 20 fractions.
Overall, the mean age was 74.2 years (SD 6.6) and the median PSA was 7.8 (IQR 4.8-10.1). The majority of patients had ISUP 2 adenocarcinoma (56%), and the remaining patients had ISUP 1 (10%), ISUP 3 (30%), and ISUP >= 4 (4%) disease. The disease risk was staged as early in 10%, favorable intermediate in 29%, unfavorable intermediate in 54%, and high in 6%; androgen deprivation therapy was used for 67% of men. Hyaluronic acid insertion was completed with a 100% success rate, and was rated as ‘easy’ to ‘very easy’ 100% of the time. Hyaluronic acid visualization on MRI is as follows:
There were no device related complications, rectal perforation, serious bleeding, infections or allergic reactions. The mean prostate size was 42 cc (IQR 31-56cc). Mean recto-prostatic separation at the base (measured 5mm below the prostate base), mid gland and apex (measured 5mm above the prostate apex) were 12 mm (SD 0.2), 11 mm (SD 0.2) and 0.9 mm (SD 0.1) respectively. The hyaluronic acid was also symmetrically placed in breadth at the mid gland in all patients. The mean rectal volume receiving 53 Gy (rV53) was 3.3% (IQR 0.3-2.7) for patients receiving 60-62 Gy of radiotherapy. Follow-up time only allowed for adequate assessment of acute rectal toxicities, of which 4% of patients experienced grade 1 gastrointestinal toxicity following treatment, and no higher grades were reported. Of these patients, 3% developed acute diarrhea and 1% developed acute anal pain.
Emily Holt concluded this presentation discussing the use of hyaluronic acid as rectal spacer in prostate cancer patients undergoing hypofractionated radiotherapy with the following concluding messages:
- Hyaluronic acid was successfully inserted in all patients, was well tolerated, and was reported as “very easy” or “easy” among all users
- Recto-prostatic separation was symmetrical in length from the base to the apex and in breadth at the mid-gland
- There was no grade 2 or greater early rectal toxicities
- These findings are consistent with the Barrigel randomized trial of hypofractionated radiotherapy where the risk of early grade 2 or greater rectal toxicity was significantly reduced (2.8% with Barrigel vs 14.5% control)
- These findings support the use of hyaluronic acid as a rectal spacer given its ease of application, symmetry, and low acute GI toxicities following radiotherapy
Presented by: Emily Holt, Genesis Cancer Care, Melbourne, VIC, Australia
Co-Authors: Y. Chan2, A. Tan3, M. Liu4, H. Ho1, P. Manohar5, D. Pan6, C. W. Cham7, K. McMillan8, D. Lim Joon9, T. Pham10, F. Foroudi11, M. Cokelek12, D. Bolton13, M. Ng14, M. Guerrieri14, and M. W. T. Chao15; 1Genesis Cancer Care, Melbourne, VIC, Australia, 2The Austin Hospital, Melbourne, Australia, 3The Bays Hospital, Mornington, Australia, 4Knox Private Hospital, Melbourne, Australia, 5Ringwood Private Hospital, Melbourne, Australia, 6Monash Hospital, Melbourne, Australia, 7The Bays Hospital, Melbourne, Australia, 8Monash University- Eastern Health Clinical School, Clayton, Australia, 9Austin Health, Melbourne, Australia, 10The Valley Private Hospital, Mulgrave, Australia, 11Austin Health, Radiation Oncology, Melbourne, Australia, 12Genesis Cancer Care, Melbourne, Australia, 13Olivia Newton John Cancer Centre, Melbourne, Australia, 14Genesis Care, Melbourne, VIC, Australia, 15Austin Health, Melbourne, VIC, Australia
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 2022 American Society of Radiation Oncology (ASTRO) Annual Hybrid Meeting, San Antonio, TX, Sat, Oct 22 – Wed, Oct 26, 2022.
References:
- Dearnaley D, et al. Conventional versus hypofractionated high-dose intensity-modulated radiotherapy for prostate cancer: 5-year outcomes of randomized, non-inferiority, phase 3 CHHip trial. Lancet Oncol 2016;17:1047-1060.