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    Interventional procedure overview of biodegradable spacer insertion to reduce rectal toxicity during radiotherapy for prostate cancer

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    Existing assessments of this procedure

    The Institut national d'excellence en santé et en services sociaux (INESSS, in 2021) evaluated the use of a biodegradable spacer (SpaceOAR™ Hydrogel System) in patients with localized or locally advanced prostate cancer treated with external beam radiotherapy or brachytherapy combined or not with external beam radiotherapy. Avis - Utilisation de l'hydrogel SpaceOARMD comme espaceur rectal lors de la radiothérapie de la prostate (inesss.qc.ca)

    Summary of deliberations

    Authors concluded that based on best available data and given the significant uncertainty regarding the product's therapeutic value that public coverage for the SpaceOAR™ is not supported. Additional evidence is necessary to support the adoption of this technology. Reasons for the unanimous position include:

    • The limitations in the evidence, including the absence of data for groups considered to be at higher risk for rectal toxicity;

    • The risk-benefit ratio, which does not appear to support the use of this technology;

    • The possibility of major complications for patients;

    • The possibility of an increased risk of complications for patients at increased risk for rectal toxicity;

    • The observed dosimetric benefit (sometimes significant) in the evidence presented, which appears to offer only a small clinical benefit;

    • The contradiction between the positions taken by other organizations;

    • The potential difficulty of access to MRI.

    RECOMMENDATION

    The authors concluded that more evidence on safety and efficacy is needed to recommend this technology and that it should be available only within further research.

    Cancer Care Ontario guideline (Chung 2019) provides clinical practice recommendations for the use of biodegradable spacers for prostate cancer treatment.

    Recommendation 1 states that 'biodegradable spacer insertion is a technology that may be used to decrease toxicity and maintain quality of life (QOL) in appropriately selected prostate cancer patients receiving radiotherapy (RT)'.

    • Spacer insertion should be performed by individuals trained in the use of transperineal interventional procedures and where there is institutional support.

    • Selection of appropriate patients remains to be fully defined but may include those in whom standard rectal dose-volume criteria are not met; those treated with ultrahypofractionated RT; and those at higher baseline risk of rectal toxicity.

    Interpretation of evidence for recommendation 1

    • Key evidence for this recommendation was from a multicentre RCT, (Mariados 2015), a follow-up report for this RCT (Hamstra 2017), and 3 non-randomised studies (Pinkawa 2017, Prada 2009, Te Velde 2017).

    • The authors state that 'evidence is adequate to support the use of biodegradable rectal spacers for RT in patients with localized prostate cancer. However, given the low rates of toxicity observed overall in both arms of the RCT, there may be limited benefit to routine application of this technology. Further evidence to direct the appropriate selection of patients and to evaluate the efficacy of this technology beyond conventionally fractionated RT is warranted'.

    A CADTH rapid response report of clinical and cost effectiveness on hydrogel spacers for patients with prostate cancer in 2019 included 3 systematic reviews, 1 RCT (described within 2 eligible reports), 7 cohort studies, 2 economic evaluations, and 3 guidelines. Authors concluded that 'hydrogel spacers were effective in increasing the distance between the prostate and the rectum, and in reducing the radiation dose to the rectum while delivering radiation to the prostate in patients with localized prostate cancer'. However, 2 systematic reviews reported that the clinical benefits were not significant and were therefore uncertain. One systematic review developed for a HTA did not recommend the routine use of hydrogel spacers for prostate cancer, in consideration of the high costs for their patients. In contrast, 3 year follow-up results of an RCT indicated that hydrogel spacers were associated with improvements in bowel, urinary and sexual quality of life outcomes…… 'The guidelines by Cancer Care Ontario, the National Comprehensive Cancer Network, and the National Institute for Health and Care Excellence recommended the use of hydrogel spacers to reduce rectal toxicity and improve quality of life'.

    The National Comprehensive Cancer Network (2018), in the USA states that "endorectal balloons may be used to improve prostate immobilization. Perirectal spacer materials may be employed when the previously mentioned techniques are insufficient to improve oncologic cure rates and/or reduce side effects due to anatomic geometry or other patient related factors, such as medication usage and/or comorbid conditions". It recommends that "patients with obvious rectal invasion or visible T3 and posterior extensions should not undergo perirectal spacer implantation for prostate cancer".

    A product brief from an ECRI Institute Health Technology Assessment information service (in 2017) on SpaceOAR hydrogels concluded that these devices are "well tolerated and work as intended to reduce rectal irradiation, long-term (but not acute) rectal toxicity, and improve bowel quality of life (QOL), based on 1 RCT and 3 non-RCTs". 'A comparative study found that neither SpaceOAR nor a competing spacer (BioProtect Prospace) reduced acute rectal toxicity (<3 months). Studies with longer follow-up (>5 years) that compare different spacers are needed; an ongoing study will provide 5-year data'.

    • SpaceOAR hydrogel increases perirectal space and reduces rectal irradiation, severity of late rectal toxicity, and the proportion of patients experiencing poor bowel QOL, based on results of a multicenter RCT that reported 3-year results and 3 non-RCTs of radiotherapy groups reporting shorter 3- to 12-month follow-up. No studies are available that compare SpaceOAR with hyaluronic acid or human collagen spacers.

    • SpaceOAR does not appear to reduce acute rectal toxicity during and shortly after radiation therapy (<3 months) based on controlled trial results. A study comparing SpaceOAR with the BioProtect Prospace balloon spacer found that neither device reduces acute rectal toxicity (<3 months).

    • Clinicians may need to perform at least 32 procedures before achieving optimal SpaceOAR insertion and patient outcomes, based on evidence from a retrospective, single-center comparison study.

    • SpaceOAR placement and hydrogel material appear to be well tolerated based on results from the RCT and case series.

    • RCT authors reported that no rectal perforation, hemorrhage, or infection were associated with use of SpaceOAR. Most events were mild, transient, and similar between groups. Case series (n = 683) reported few adverse events: 4 rectal wall penetrations (with dose escalation), 1 Grade 3 telangiectasia, and 1 asymptomatic necrotic rectal lesion.

    • Longer-term (>5 years) and comparative data are needed because late effects can occur many years after prostate irradiation. A single-arm post-marketing study is collecting 5-year data on 250 patients.