When do you use a rectal spacer in combination with radiotherapy for prostate cancer?

We have done this in a few patients with high risk of complications ( history of IBD) with LDR brachytherapy. The procedure as suggested is done at the end of brachytherapy to avoid interference with ultrasound imaging. The spacer increased the distance and helped decrease the dose to rectum significantly. Moving forward, we plan to use this with combined modality as these patients are at increased risk of grade 2 to 3 rectal bleeding.

This is our early data.

Also based on recent CHHIP data:

Wilkins et al., IJROBP 2020

Space OAR would be needed to meet tighter anorectum constraints of V60Gy <0.01%.

I have been using hydrogel spacer in patients receiving external beam radiation therapy. This includes IMRT and proton therapy for now but I see no reason not to use it in patients also getting SBRT. The phase III trial selected patients with low and low-intermediate risk disease specifically to avoid the risk of injecting the gel into a region where microscopic extracapsular extension could preside. One thing that we don't want to do is risk pushing cancer cells away from the CTV. For this reason, I do not use it in High Risk cases. I believe the use of hydrogel in brachytherapy cases would also improve the rectal tolerance to treatment but the data for this indication is not yet available. If I were to use it in brachytherapy cases, it wo...