An absorbable gel or balloon between prostate and rectum before radiotherapy, used under audit

What it is. Before prostate radiotherapy, a hydrogel, hyaluronic acid or a biodegradable balloon is placed through the skin between the prostate and the rectum under ultrasound, creating a gap of about a centimetre that lasts through treatment and is absorbed afterwards.

The randomised evidence. In the pivotal hydrogel trial, 222 men having 79.2 Gy in 44 fractions were randomised to spacer or none. The spacer created 12.6 millimetres of separation against 1.6 in controls, cut the rectal volume receiving 70 Gy from 12.4 to 3.3 per cent, and late rectal toxicity at 3 to 15 months was 2.0 against 7.0 per cent; 11.6 against 21.4 per cent of men had a meaningful decline in bowel quality of life at 15 months. A meta-analysis of one randomised trial and six cohort studies with 1,011 men found late grade 2 or worse rectal effects of 1.5 against 5.7 per cent (risk ratio 0.23, 95 per cent confidence interval 0.06 to 0.99). With four-week hypofractionated treatment, a randomised trial of a hyaluronic acid spacer in 201 men found acute grade 2 or worse bowel effects in 2.9 against 13.8 per cent.