Tuesday, 10 March 2009

Cryoablation: A New Tool In The Oncologists Toolbox

Prostate cancer treatment, while generally quite successful when the cancer is caught at an early stage, isn't without its problems. In the short term, radiation therapy and surgery can damage closely associated nerve bundles and cause incontinence and impotence. In the long term, resistance to therapy can develop, limiting the treatment options available. A new treatment option pioneered by doctors at the Center for Safer Prostate Cancer Therapy in Orlando, USA is an effective solution to these problems.

Cryoablation (or cryotherapy) is a minimally invasive technique where a needle is inserted through the skin and into the prostate tumor, guided to the exact location with 3D imaging. Once the head of the needle is in place, a argon gas is circulated through the needle tip, reducing its temperature and freezing the surrounding tumor tissue. Freezing is a highly effective method of tumor killing as the formation of ice crystals within the cell spear through the membranes and simply destroy the whole cell structure, whereas radiation therapy relies on DNA damage and cell suicide, a process which tumors often grow resistant to. The treatment uses two freeze cycles with an intermediate thawing step to ensure cell kill.

The study at the center followed 120 men who had cryoablation. The patients were monitored for 12 years, after which 93% showed no signs of cancer recurrence, despite more than half of them initially being assessed as at high risk of cancer recurrence. Furthermore, in the 7% of patients whose cancer did return, it was located elsewhere in the prostate gland and further cryoablation was used successfully in treating those cases, resulting in 100% effective disease management. All patients retained full bladder control and only 15% experienced impotence.

The treatment isn't exclusive to prostate cancer, great success has also been seen in kidney cancer. Doctors at Johns Hopkins Hospital in Baltimore have tested it on 90 tumors in 84 patients and observing for 3 years (two years longer than is standard for kidney treatments). They have seen 100% efficacy on tumors of 4cm or less in size, close to 100% in tumors up to 7cm in size, and two of three 10cm tumors were successfully killed. 75% of kidney tumors are less than 4cm in size at the time of diagnosis so cryoablation is a very real option for the majority of cases. Indeed, the doctors argue that the procedure should become the gold standard, replacing the current surgery which involes several days in hospital with an outpatient procedure that preserves as much kidney as possible.

Data for both studies was presented at the Society of Interventional Radiology's 34th Annual Scientific Meeting.

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