Biodegradable spacer insertion to reduce rectal toxicity during radiotherapy for prostate cancer

2.1 Prostate cancer is the most common cancer in men, and the second most common cancer in the UK. Most prostate cancers are either localised or locally advanced at diagnosis. Localised prostate cancer often does not cause any symptoms, but some people might have urinary problems or erectile dysfunction. Some people may not identify as men but may have a prostate.

2.2 Current treatment options for localised or locally advanced prostate cancer include 'watchful waiting', active surveillance, radiotherapy, radical prostatectomy, transurethral resection of the prostate, cryotherapy, high-intensity focused ultrasound, androgen deprivation therapy and chemotherapy (as recommended in NICE's guideline on prostate cancer: diagnosis and management).

2.3 Radiation therapy is an established curative treatment and can be either external-beam radiotherapy or brachytherapy (also called interstitial radiotherapy). Brachytherapy can be given at low or high dose rates. Low dose rate brachytherapy may be used alone or with external-beam radiotherapy.

2.4 Radiotherapy for prostate cancer can cause rectal damage because of the close proximity of the prostate and the rectum. Symptoms of rectal damage can include diarrhoea, incontinence, proctitis and ulceration of the rectal mucosa. Injecting a biodegradable substance (examples include polyethylene glycol hydrogel, hyaluronic acic and human collagen), or inserting and inflating a biodegradable balloon spacer in the space between the rectum and prostate is done to temporarily increase the distance between them. The aim is to reduce the amount of radiation delivered to the rectum and reduce the toxicity profile during prostate radiotherapy.

2.5 The procedure can be done with the patient under general, spinal or local anaesthesia using transrectal ultrasound guidance. The patient is placed in the dorsal lithotomy position. For gel injection, a needle is advanced percutaneously via a transperineal approach into the space between the prostate and the rectum. Hydrodissection with saline may be used to separate the prostate and the rectum for some gels, but is not always necessary. After confirming the correct positioning of the needle, the gel is injected, filling the perirectal space. Some of the gels may polymerise to form a soft mass and some do not. The biodegradable gel absorbs slowly over several months. Some gels are reversible and can be dissolved using enzymes. For balloon spacer insertion, a small perineal incision is typically used to insert a dilator and introducer sheath. The dilator is advanced towards the prostate base over the needle, which is then removed. A biodegradable balloon is introduced through the introducer sheath and is filled with saline and sealed with a biodegradable plug. The balloon spacer degrades over several months.