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

The condition

2.1 Prostate cancer is the most common cancer in men, and the second most common cancer in the UK. There is a NICE clinical guideline on the diagnosis and management of prostate cancer. 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.

Current treatments

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 clinical guideline on prostate cancer: diagnosis and treatment).

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

The procedure

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 acid, 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 is usually done with the patient under general anaesthesia using transrectal ultrasound guidance, but it may also be done using local or spinal anaesthesia. The patient is placed in the dorsal lithotomy position. For gel injection, a needle is advanced via a transperineal approach into the space between the prostate and the rectum. Hydrodissection with saline is then used to separate the prostate and the rectum. After confirming the correct positioning of the needle, the hydrogel precursors are injected, filling the perirectal space. These then polymerise to form a soft mass. The biodegradable hydrogel absorbs slowly over several months. 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.