Since the 1960s, cryotherapy has been used to destroy skin tumours, precancerous skin moles, nodules, skin tags or unsightly freckles. It also has been used to destroy retinoblastomas, a childhood cancer of the retina. With the improvement of imaging techniques and the development of devices to better control extreme temperatures, physicians have begun to perform cryotherapy for prostate, liver, and cervical cancer, especially if surgery is not possible. Currently, research is being done to determine the effectiveness of cryotherapy for tumours of the bone, brain, kidney, lung and spine. Researchers are also evaluating its usefulness in freezing and shrinking benign breast lumps, called fibro adenomas.
Some medical professionals, particularly those who specialize in sports medicine, use the term cryotherapy to refer to the application of cold to muscles and joints that are sore or fatigued after physical exertion. However, this is not related to the radiologic-based technique described here.
No special preparation is needed to undergo cryotherapy, although some physicians recommend ibuprofen (400 mg) a half hour before the procedure to relieve minor discomfort. Establishment of an intravenous line provides access for additional sedation drugs. Any potential bleeding problems will usually have been identified in advance by blood tests. Some physicians administer a dose of antibiotics before cryotherapy as a way to guard against infection.
Cryotherapy is carried out by using a cryoprobe, a thin wand-like device with a handle or trigger or a series of small needles, attached via tubing to a source of nitrogen or argon, which super-cools the probe tip. Most cryotherapy units use argon gas and are approved by the U.S. Food and Drug Administration (FDA) for general urologic and oncologic uses. The cryoprobe is placed in the proper position using imaging guidance, and as internal tissue is being frozen, the physician avoids damaging healthy tissue by viewing the movement of the probe on live ultrasound, computed tomography (CT), or magnetic resonance (MR) images transmitted to a monitor similar to a television screen.
Living tissue, healthy or diseased, cannot withstand extremely cold conditions and dies from:
- Ice within the cell. At approximately -40°C (-40°F) or less, intracellular lethal-ice crystals begin to form that will tear almost any cell apart.
- Bursting from swelling or shrinking. If ice forms only outside the cell, osmosis—the movement of a solution through the membrane of a cell—causes the cell to shrink as it gives up water to replace the water that has turned to ice. Then, as the area thaws, water rushes into the shrunken cell and causes it to burst. For this reason, cryotherapy usually consists of a series of steps in which tumours are repeatedly frozen and thawed.
- Loss of blood supply. Cells die when their blood supply is choked off by ice forming within small tumour vessels, causing clotting. Since the average blood-clotting time is approximately 10 minutes, the extreme cold is maintained for at least 10 minutes unless tumour temperatures indicate that lethal-ice temperatures have been reached.
Once the cells are destroyed, components of the immune system, primarily the white blood cells, clear out the dead tissue. There is some evidence to suggest that this procedure also stimulates the immune system to attack remaining cancer cells.
For external masses, liquid nitrogen is applied directly with a cotton swab or spray device. For internal tumours, liquid nitrogen or argon gas is circulated through the cryoprobe, which comes into contact with the diseased tissue.
More advanced forms of cryotherapy, such as for treatment of liver cancer, involve the insertion of the probe through an incision or threaded through the skin. Then, by using an imaging device such as ultrasound or computed tomography (CT), the physician targets and freezes the tumour. For lung cancer, the probe is passed through a bronchoscope, an instrument used to examine the trachea and bronchi, and placed on the abnormal tissue, or several straw-thin cryoprobes are inserted through a tiny skin incision and guided by computed tomography (CT) to the lung tumour. Likewise, for prostate cancer, six to eight needle probes can be inserted through the perineum (between the rectum and pubic areas) and ultrasonically guided to freeze the cancer.
Intraoperative cryotherapy procedures, such as for the liver or kidney, require general anaesthesia since the abdomen is opened through an incision or air is pumped into the abdomen for a laparoscopy, an examination using an illuminated tube. You would be unconscious for the entire procedure and monitored by an anaesthesiologist.
Percutaneous (through the skin) cryotherapy can be done with the patient fully conscious by using only local anaesthesia. Xylocaine or a similar medication is injected throughout the tissues overlying the tumour where the probes go through. You may feel a brief pinch and burning sensation during the injection, much like when a dentist administers procaine (Novocaine) or another similar medication. Other than the administration of the local anaesthesia, the most common discomfort is having to be still for up to two hours. Intravenous sedation can be given to help patients relax while on the table for computed tomography (CT) or magnetic resonance (MR) imaging. Patients with joint discomforts may require intravenously administered sedation to hold still.
Generally, patients undergo cryotherapy either because a referring physician has recommended it or a cancer specialist, after analyzing the patient’s condition and all available medical history, has decided it is the best way to treat the cancer.
- The performance of intraoperative cryotherapy that performed during surgery, requires the combined skills of a cancer surgeon and an interventional radiologist.
- The performance of percutaneous cryotherapy requires only an interventional radiologist since the procedure is done in the radiology department, rather than the operating room. Cryotherapy devices, which are 2-3 mm (about one-tenth of an inch) in diameter, are inserted through skin incisions. This is done by using ultrasound, computed tomography (CT), or magnetic resonance (MR) imaging to determine the position of the devices.
- Prostate cryotherapy is usually performed by a urologist, but experienced radiologists at some medical centers may also perform this procedure.
Your cancer specialist will determine the results of the procedure and send the results to your referring physician. It may take a few more weeks for the cancer specialist to determine the extent of treatment success. Once known, this information will also be sent to your referring physician, who will give the information to you.