Cryosurgery for Prostate Cancer Explained

Standard treatment modes for localized prostate cancer includes surgery (radical prostectomy), radiotherapy and active monitoring of the disease. Cyroablation has been gaining popularity as a minimally invasive treatment option for primary and recurrent prostate cancer during the past decade. Cryotherapy (or cryosurgery) is the application of extreme cold to destroy the abnormal or diseased tissue. Cryosurgery kills the cancer cells by direct cell injury caused by ice crystal formation, leading to failure of cellular metabolism and vascular statis (stagnation of blood circulation) caused by disruption of micro-circulation. Freezing of extracellular water causes hyperosmotic shock leading to denaturation (alterations in the shape of molecules leading to loss of its activity) and electrolyte imbalance. During the process of thawing ice crystals fuse to form larger crystals leading to the disruption of cell membrane. Damage to endothelial cells (cells lining the interior surface of blood vessels) leads to platelet (cell fragments involved in blood clot formation) aggregation and microthrombi (blood clot) formation leading to vascular stasis. A minimum freezing temperature of -40C for at least 3 minutes and a minimum of two freeze-thaw cycles are recommended for effective tumor eradication.

Although, cryosurgery for prostate cancer was used as early as 1960, it got greater attention in early 1990’s when Onik and his collegues combined percutaneous (any medical procedure where access to inner organs is done via needle-puncture of the skin, rather than by using an “open” approach where inner organs or tissue are exposed) technique with real time transrectal ultrasound (ultrasound based medical imaging for visualization of the internal organs). This lead to accurate placement of cryoprobes, real time monitoring, control of freezing and minimal injury to the rectum. Current day multicryoprobes use argon-helium system. These gases undergo specific temperature changes (an increase or decrease) when decompressed by a mechanism known as Joule-Thomson or Joule-Kelvin effect. The property of argon makes it ideal for cooling, whereas helium is used for thawing and rewarming.

The major adverse effects of cryoablation in erectile dysfunction (inability to develop or maintain an erection of the penis), caused due to anatomical juxtaposition of the cavernous nerve bundles (help in erectile function) to the apex of prostate. Although no clinical trials or evidence is available to evaluate the efficacy of cyrosurgery, clinical series have emerged with acceptable cancer control and morbidity. Cryosurgery procedure requires careful patient selection and technical expertise to achieve appreciable level of tumor control, patient satisfaction and quality of life.