What is cryotherapy for prostate cancer?
The type of treatment for prostate cancer largely depends on the stage and grade of cancer.
The stage of prostate cancer basically describes the location of cancer within the body. Prostate cancer can be divided into:
- Localised cancer (the cancer has not spread to other areas of the body and only affects the prostate).
- Locally advanced cancer (the cancer has spread outside the capsule of the prostate but not to other areas of the body).
- Metastatic cancer (the cancer has spread outside the prostate to other areas of the body).
The grade of cancer refers to how abnormal the cancer cells look under the microscope after a prostate biopsy. This determines the aggressiveness and growth rate of the cancer cells. It can be divided into:
- Grade group 1 (Gleason score 6): this is considered low grade.
- Grade group 2 and 3 (Gleason score 7): this is considered intermediate grade.
- Grade group 4 and 5 (Gleason score 8-10): this is considered high grade.
For men with low grade localised prostate cancer, close observation (active surveillance) instead of treatment is a good option, allowing them to avoid the harms of treatment. In these men, treatment is only initiated if there are signs of cancer growth while on surveillance.
However, for intermediate and high grade localised cancer, treatment is usually advised due to the high risk of cancer growth and spread. The standard treatment is usually either surgery to remove the prostate (radical prostatectomy) or radiotherapy treatment of the prostate.
Issues with standard treatment
Surgery or radiotherapy, which are also known as whole gland treatment as the entire prostate is removed or irradiated, can potentially result in urine incontinence (leakage of urine) and erectile dysfunction (problems getting or maintaining an erection) in some patients. The reason is that the nerves, blood vessels, and muscles that determine urine control and erection are in close proximity to the prostate gland and are thus often damaged in whole gland treatments. In addition, for patients undergoing radiotherapy, there may be risk of damage to the surrounding organs such as the bladder and rectum.
What is cryotherapy for localised prostate cancer?
With the advent of more accurate MRI-targeted prostate biopsies in the last few years, some patients are diagnosed with cancer only involving only a small proportion of the prostate. In these men, the logical thought is whether treatment can be focused only on these areas of cancer without needing a whole gland treatment.
Prostate cryotherapy is a surgical technique that can be focused on treating these areas of prostate cancer (also called ‘focal therapy’). Cryotherapy uses extremely cold temperatures to freeze and destroy the prostate cancer cells. The procedure is done under general anaesthesia, and probes are placed through the perineal skin into the area of prostate cancer under close ultrasound monitoring. The areas of cancer are then frozen and destroyed.
What are the risks of focal cryotherapy for localised prostate cancer?
All treatments unfortunately have risks. For focal cryotherapy, these can include:
- Some men will have difficulty passing urine after treatment. Patients will have a tube (catheter) inserted into the bladder during the procedure to help with this. The catheter is usually left in place for about one week.
- Some men will notice swelling of their penis or scrotum. This usually disappears within a month or two.
- Occasionally, patients may develop tingling or numbness around the penis. This usually resolves within three months.
- About one in five men may have pain around or in the rectum (back passage), but this usually settles within three months.
- Tissue fragments may pass out in the urine in up to 5% of patients. This may lead to pain or difficulty in passing urine.
- Erectile dysfunction is uncommon, occurring in up to one in five men based on studies.
- Urine incontinence is rare, occurring permanently in up to 2% of patients, based on studies.
- A rare and serious consequence (about 0.1% risk) is the formation of an abnormal connection between the rectum and the urethra (the tube which carries urine), also known as a fistula. The formation of a fistula can be caused by the rectum being frozen during cryotherapy treatment. This complication is serious and may require an operation to repair the hole.
Who is suitable for cryotherapy treatment?
Based on expert consensus, the ideal patient for focal cryotherapy is someone with a small area of intermediate grade cancer localised within the prostate, who has undergone an accurate MRI-targeted and systematic biopsy to exclude aggressive cancer outside the proposed area for focal cryotherapy.
Can focal cryotherapy really cure localised prostate cancer?
Unfortunately, there is a lack of long-term data (with follow-up for more than ten years after treatment) on the effectiveness of focal cryotherapy in treating prostate cancer. It is still not considered a standard treatment for localised prostate cancer, compared to surgery or radiotherapy. However, based on what we know from the studies so far, the risk of prostate cancer death after focal cryotherapy is not any different from surgery or radiotherapy within the first ten years of treatment. Most of these studies find that approximately 20-30% of prostate cancer can persist or recur after focal cryotherapy. However, these men may be suitable for a repeat course of focal cryotherapy, eventually achieving excellent cancer control.
In summary, in carefully selected patients, about 70-80% may only require one session of focal cryotherapy for their localised prostate cancer. A second focal cryotherapy session may be required in the 20-30% of men whose cancer persist or recur.
How do we determine if cryotherapy treatment is effective?
Continued follow up is required after focal cryotherapy to determine if the cancer has been successfully treated. The Prostate Specific Antigen (PSA) blood test is usually checked at 3 months after treatment, and then often at half-yearly intervals. This is to ensure that the PSA level drops and remains low after treatment. An MRI scan of the prostate is also usually performed at 6-12 months after treatment, to ensure that no tumour is visible on the MRI scan. The MRI scan may be repeated periodically as part of the follow up. Finally, a repeat prostate biopsy may be required at about a year after treatment, or if the PSA or MRI shows signs of cancer recurrence or progression.
Cryotherapy for prostate cancer. Probes are placed through the perineal skin to deliver the treatment, which will freeze and destroy the prostate cancer cells located around the probes.
Planning and marking the area of the prostate to be treated with focal cryotherapy.
Monitoring treatment with visualisation of the “ice ball”, showing area of prostate being treated during cryotherapy.