MDNews - San Antonio

Radiation therapy has been used to treat prostate cancer since the early 20th century. Relatively recent improvements, such as inten- sity-modulated radiotherapy (IMRT) and the addition of image guidance, have improved the delivery accuracy and outcomes of treatment. Even with advances in targeting such as IMRT and image guidance, some patients still experience significant acute and long-term bowel, urinary and sexual side effects. The rectum mucosa is very sensitive to radiation injury. Its immediate proximity to the prostate makes the rectum the primary organ at risk (OAR) during prostate radiation therapy. Too much rectum radiation exposure can result in long-term abdominal pain, diarrhea, incontinence, bleeding and mucus discharge. Three recent, prospective clinical trials found late grade 2+ gastrointes- tinal toxicity rates ranging from 14% to 25% in the 3 to 5 years following conventional prostate radiotherapy .1–4 SpaceOAR™ Hydrogel (Boston Scientific, Marlborough, MA) has been developed to address the issue of rectum proximity and minimize rectal radiation injury by displacing the rectum away from the prostate during radiation therapy (Figure 1). SpaceOAR Hydrogel is an in situ curing polyethylene glycol (PEG)-based Hydrogel that maintains space for 3 months and then absorbs within about 6 months. It is the first and only commercially available absorbable spacer proven to significantly reduce rectum radiation dose during prostate radiation therapy, thereby improving the odds of preserved bowel and urinary quality of life (QOL) following radiotherapy. 5–8 In a 15 month, multicenter, randomized, controlled clinical trial, SpaceOAR Hydrogel safely created an average of over 1cm or .5 in of space to separate the prostate from the rectum. 5 At median three year follow up, this study also demonstrated that: 5–8 • Relative to control patients without spacer placement, men with SpaceOAR Hydrogel received significantly less radiation dose to the rectum and penile bulb; and had less decline in patient- reported urinary and bowel QOL at median 3 years; • From 3 months onward, no SpaceOAR Hydrogel patients experienced grade 2 or greater rectal toxicity (e. g., proctitis, bleeding, fecal incontinence); and • Among baseline-potent men, the percentage of patients retaining erections sufficient for intercourse at What every Urologist needs to know about SpaceOAR ™ Hydrogel. How Boston Scientific is protecting QOL for prostate cancer patients. 1. Dearnaley D, Syndikus I, Mossop H, et al; CHHiP Investigators. Conventional versus hypofractionated high-dose intensity-modulated radiotherapy for prostate cancer: 5-year outcomes of the randomised, non-inferiority, phase 3 CHHiP trial. Lancet Oncol. 2016 Aug;17(8):1047-60. 2. Aluwini S, Pos F, Schimmel E, et al. Hypofractionated versus conventionally fractionated radiotherapy for patients with prostate cancer (HYPRO): late toxicity results from a randomised, non-inferiority, phase 3 trial. Lancet Oncol. 2016 Apr;17(4):464-74. 3. Wortel RC, Incrocci L, Pos FJ, et al. Late side effects after image guided intensity modulated radiation therapy compared to 3D-conformal radiation therapy for prostate cancer: results from 2 prospective cohorts. Int J Radiat Oncol Biol Phys. 2016 Jun 1;95(2):680-9. 4. Catton CN, Lukka H, Gu CS, et al. Randomized trial of a hypofractionated radiation regimen for the treatment of localized prostate cancer. J Clin Oncol. 2017 Jun 10;35(17):1884-90. 5. Mariados N, Sylvester J, Shah D, et al. Hydrogel spacer prospective multicenter randomized controlled pivotal trial: dosimetric and clinical effects of perirectal spacer application in men undergoing prostate image guided intensity modulated radiation therapy. Int J Radiat Oncol Biol Phys. 2015 Aug 1;92(5):971-7. 6. Hamstra DA, Mariados N, Sylvester J, et al. Continued benefit to rectal separation for prostate radiation therapy: final results of a phase III trial. Int J Radiat Oncol Biol Phys. 2017 Apr 1;97(5):976-85. 7. Karsh LI, Gross ET, Pieczonka CM, et al. Absorbable Hydrogel spacer use in prostate radiotherapy: a comprehensive review of phase 3 clinical trial published data. Urology. 2018 May;115:39-44. 8. Hamstra DA, Mariados N, Sylvester J, et al. Sexual quality of life following prostate intensity modulated radiation therapy (IMRT) with a rectal/prostate spacer: secondary analysis of a phase 3 trial. Pract Radiat Oncol. 2018 Jan-Feb;8(1):e7-e15. 9. Data on file with Boston Scientific. The SpaceOAR Hydrogel procedure patients are placed in a lithotomy position and anesthetized (using general anesthesia, conscious sedation or local anesthesia) (Figure 2). Using stepper-mounted side-fire transrectal ultrasound guidance, an 18-gauge needle is advanced through the perineum and into the perirectal fat posterior to Denonvilliers' fascia and anterior to the rectal wall. Saline is then injected through the needle at mid-gland to expand the perirectal space. Following confirmation of proper needle location via ultrasound, aspiration is per- formed to ensure the needle is not intravascu- lar. The PEG Hydrogel precursors are injected through the needle into the previously hydrodissected space (Figure 3). The precursors polymerize within 8 to 10 seconds to form a soft Hydrogel spacer (Figure 4). The Hydrogel is designed to remain dimensionally stable for 3 months during radiotherapy and then liquefy via hydrolysis within 6 months (Figure 5). The material is then absorbed and cleared via renal filtration. Without SpaceOAR Hydrogel Prostate High radiation dose Rectum With SpaceOAR Hydrogel SpaceOAR Hydrogel Prostate High radiation dose Rectum Figure 1. Normal prostate anatomy vs. prostate anatomy with SpaceOAR Hydrogel

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