Focal therapy using cryoablation for localised prostate cancer

2.1 Indications and current treatments

2.1.1 Symptoms of localised prostate cancer include difficulty in passing urine, although the condition is often diagnosed at an asymptomatic stage.

2.1.2 Treatment options for patients with localised prostate cancer include active surveillance, radical prostatectomy, external beam radiotherapy, brachytherapy, and ablation of the whole gland using cryotherapy or high-intensity focused ultrasound (HIFU). All radical treatment options are associated with substantial risks of sexual, urinary or bowel dysfunction. Focal therapy using cryoablation is intended to be used in patients with localised prostate cancer – specifically patients with tumours that are confined to 1 prostatic lobe.

2.2 Outline of the procedure

2.2.1 Imaging and biopsy mapping studies are used to confirm that the tumour is suitable for focal therapy and to show its precise location. Using local or general anaesthesia, the bladder is catheterised. Using transrectal ultrasound and a template placed on the perineum, fine needles are inserted transperineally into the prostate. Pressurised argon is passed through the needles to freeze the targeted area of the prostate, destroying the tissue. Implantable temperature probes and transrectal ultrasound guidance are used to monitor the treatment, and steps are taken to protect surrounding tissue from the effects of freezing.

2.2.2 After treatment patients are usually followed up regularly with prostate-specific antigen (PSA) measurements, imaging, and repeated biopsies to detect recurrence.

2.3 Efficacy

2.3.1 A case series of 54 patients reported overall and disease-specific survival of 100% of 48 patients at mean 4.5-year follow-up. In a register report of 1160 patients treated by focal cryoablation (total 5853 patients), the biochemical recurrence-free rate (as defined by the American Society for Therapeutic Radiation and Oncology [ASTRO]) was 76% (absolute numbers not given) at 3-year follow-up. Two case series of 54 and 60 patients reported biochemical recurrence-free survival of 94% (45/48) and 80% (41/51) of patients at mean 2-year and 15-month follow-up respectively. In a case series of 25 patients 36% (9/25) were considered to be biochemically disease-free (defined as a PSA nadir of 1.0 ng/ml or less) at median 28-month follow-up.

2.3.2 In the register report of 1160 patients, 164 patients underwent biopsy because of increased post-treatment serum PSA levels. Of these, 26% (43/164) had a positive biopsy at median 21-month follow-up. The case series of 60 patients reported positive findings in 40% (14/35) of patients who had a follow-up biopsy (tumours were in the untreated lobe except for 1 patient who had a positive biopsy result from the lobe that was treated by the procedure; this patient was treated with whole gland cryoablation). Eleven of these patients were treated with a second focal cryoablation procedure, after which 73% (8/11) were biochemically disease-free at mean 15-month follow-up. In the case series of 25 patients, 28% (7/25) had repeat biopsies and residual or recurrent cancer was found in 3 of these patients. All of these patients underwent repeat focal cryoablation and were biochemically disease-free at median 28-month follow-up.

2.3.3 The Specialist Advisers listed key efficacy outcomes for this procedure as biochemical disease-free survival and biopsy-proven absence of cancer.

2.4 Safety

2.4.1 Sixty-seven per cent (40/60) of patients who were sexually potent before treatment became impotent immediately after treatment in the case series of 60 patients. Seventy-one per cent (24/34) of patients for whom data were available at 12-month follow-up had regained potency. In the case series of 54 patients 90% (36/40) of the patients who were potent before treatment remained potent after treatment.

2.4.2 With regard to urinary continence, the case series of 54 and 25 patients reported that all patients were continent after treatment. The case series of 60 patients reported incontinence in 4% (2/55) of the patients followed up for more than 6 months (neither patient required incontinence pads). The register report of 1160 patients reported urinary incontinence in 2% (8/507) of patients at 12-month follow-up.

2.4.3 Rectourethral fistula was reported in less than 1% (1/1160) of patients in the register report of 1160 patients at 12-month follow-up. In all 4 case series, there were no reports of fistulae developing after the procedure.

2.4.4 Prolonged urinary retention (> 30 days) was reported in 1.2% (6/518) of patients at 12-month follow-up in the register report of 1160 patients.

2.4.5 The case series of 54 patients reported that 1 patient required a transurethral prostatectomy for the removal of sloughed tissue.

2.4.6 The Specialist Advisers listed adverse events reported in the literature as erectile dysfunction and incontinence. They considered theoretical adverse events as urinary tract infection and pain.

2.5 Other comments

2.5.1 The Committee was mindful of the variable natural history of prostate cancer: this underpinned the recommendation for controlled studies and the need for details of long-term outcomes.

2.5.2 The Committee noted the potential for this procedure to avoid many of the complications of more radical treatments for localised prostate cancer in properly selected patients, if further evidence supports its efficacy.

2.5.3 The Committee noted a number of patient commentaries that described benefits from the procedure, but which reported instances of sexual dysfunction.

2.5.4 The Committee noted variation in the methods used to deliver focal therapy using cryoablation for localised prostate cancer and that techniques are continuing to evolve.