The 2024 ASTRO annual meeting included a session on prostate cancer, featuring a presentation by Dr. LaToya McLean discussing feasibility, safety, and toxicity of hyaluronic acid rectal spacer in locally recurrent prostate cancer with prior radiation receiving stereotactic body radiotherapy.
Hyaluronic acid injected between the prostate and rectum is commonly used in patients undergoing definitive external beam radiotherapy for prostate cancer given its ease of custom administration, favorable dosimetric advantages, and lower rates of gastrointestinal toxicity [1]. At the 2024 ASTRO annual meeting, Dr. McLean and colleagues reported the novel use of hyaluronic acid in patients undergoing repeat local therapy with stereotactic body radiotherapy.
This study was a retrospective review of 23 patients at a single institution with recurrent prostate cancer localized to the prostate, seminal vesicles, and/or prostate fossa with prior local therapy including external beam radiotherapy, brachytherapy, or cryoablation +/- prostatectomy:
Patients underwent hyaluronic acid injection into the perirectal space +/- fiducial marker insertion prior to stereotactic body radiotherapy for 35 Gy in 5 fractions. There were 17 patients treated with daily MR-guidance stereotactic body radiotherapy. The endpoints included: (i) hyaluronic acid safety, (ii) tissue separation, (iii) ease of placement, and (iv) treatment toxicity.
Prior radiation was completed over 5 years ago in 80% of patients. Patients included had prior local therapy as listed below:
- External beam radiotherapy alone: 8
- Prostatectomy with postoperative external beam radiotherapy: 6
- Brachytherapy: 7
- External beam radiotherapy with salvage cryotherapy: 1
- Cryotherapy: 1
To place the hyaluronic acid, all patients received local anesthetic with no procedure taking greater than 30 minutes. Hyaluronic acid was able to be placed with 100% success rate, there were no adverse events, and no saline dissection was used. The mean minimum GTV-rectum separation was 8.6 (± 5.6) mm, and the mean GTV was 6.5 cm3 (± 6):
The implant was rated as adequately separating the recurrence in 86.9% of cases, there was no rectal wall invasion in any patients, and all patients subsequently completed their re-irradiation with 35Gy in 5 fractions. There was one case of grade 1 gastrointestinal toxicity related to pretreatment bowel preparation managed with probiotics. There were no cases of acute grade 3+ urinary toxicity, and 1 case of late grade 3 hemorrhagic cystitis, which was ongoing in a patient that had initial definitive external beam radiotherapy:
The mean Dmax, D30%[Gy], D60%[Gy], and V30Gy were 22.9 Gy (± 6.9), 7.0 Gy (± 3.2), 3.4 Gy (± 2.5), and 0.2 Gy (± 0.4), respectively:![The mean Dmax, D30%[Gy], D60%[Gy], and V30Gy were 22.9 Gy (± 6.9), 7.0 Gy (± 3.2), 3.4 Gy (± 2.5), and 0.2 Gy (± 0.4), respectively](/images/com-doc-importer/180-astro-2024/astro-2024-hyaluronic-acid-rectal-spacer-in-locally-recurrent-prostate-cancer-with-prior-radiation-receiving-sbrt-feasibility-safety-and-toxicity/image-4.jpg)
Dr. McLean concluded her presentation by emphasizing that injection of hyaluronic acid in patients undergoing retreatment with stereotactic body radiotherapy for locally recurrent prostate cancer is safe and feasible and should be considered in select patients.
Presented by: LaToya McLean, MD, Thomas Jefferson University, Philadelphia, PA
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Wellstar MCG Health, @zklaassen_md on Twitter during the 2024 American Society for Radiation Oncology (ASTRO) Annual Meeting, Washington, DC, Sun, Sept 29 – Wed, Oct 2, 2024.
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