They are also known as cryosurgery.
It is a procedure commonly used in the office to treat a variety of benign and malignant lesions.
In one report, cryotherapy was the second most common procedure in the office after skin removal. The destruction mechanism in cryotherapy is necrosis, which results from the freezing and thawing of cells.
The treated areas are re-epithelialized. The adverse effects of cryotherapy are generally short-lived.
Something of its history
Dermatologists have used cryotherapy for a century. After developing the vacuum flask to store sub-zero liquid elements, such as nitrogen, oxygen, and hydrogen, the use of cryotherapy increased dramatically.
In the 1940s, liquid nitrogen became more readily available, and the most common method of application was using a cotton applicator.
In 1961, Cooper and Lee introduced a closed system apparatus to spray liquid nitrogen. At the end of the 60s, metal probes became available. In 1990, 87% of dermatologists used cryotherapy in their practice.
The general advantages of cryotherapy are its ease of use, low cost, and good cosmetic results. Most skin cancers are treated with excision or other destructive procedures, such as electrodesiccation and curettage.
Cutaneous superficial basal cell cancers and Bowen’s disease can be treated with cryotherapy.
The recurrence rates of primary basal cell carcinoma vary according to the treatment modality. The 5-year recurrence rate for cryotherapy can be as low as 7.5% if the lesions are chosen judiciously.
This percentage compares favorably with recurrence rates published after other procedures. Published rates include surgical excision, 10.1%; Curettage and electrodesiccation, 7.7%; Radiotherapy, 8.7%; And all non-Mohs modalities, 8.7%.
Because these percentages are derived from several studies, instead of a randomized controlled study comparing different modalities, they should be considered approximate approximations.
Well-circumscribed tumors are the most suitable for cryotherapy. The local growth of these well-circumscribed tumors explains the high cure rates cited in the literature.
In most cases, cryotherapy treatment of skin cancers is at the same rate as the destruction of benign lesions.
Mechanism of action
The mechanism of action in cryotherapy can be divided into 3 phases: (1) heat transfer, (2) cell injury, and (3) inflammation.
The mechanism by which cryotherapy destroys cells is the rapid transfer of heat from the skin to a heat sink. The most commonly used cryogen is liquid nitrogen, which has a boiling point of -196 ° C.
The heat transfer rate depends on the temperature difference between the skin and liquid nitrogen.
When the cryotherapy spray technique is used, liquid nitrogen is applied directly to the skin, and evaporation occurs (boiling heat transfer). The. The heat in the skin is transferred rapidly to liquid nitrogen.
This process results in the liquid nitrogen evaporating (boiling) almost immediately.
When a cryoprobe is used for cryotherapy, conduction heat transfer occurs when heat is transferred through the copper-metal probe.
The cell injury occurs during the thaw, after the cell freezes. Due to hyperosmotic intracellular conditions, ice crystals do not form up to -5 ° C to -10 ° C.
The transformation of water into ice concentrates the extracellular solutes and results in an osmotic gradient across the cell membrane, causing further damage.
Rapid freezing and slow thawing maximize tissue damage to epithelial cells and are most suitable for treating malignant tumors.
Fibroblasts produce less collagen after a rapid thaw. Therefore, a quick thaw may be more suitable for treating keloids or benign lesions in areas prone to scarring.
Freeze damage can be seen when a filet is defrosted from the freezer. The meat juices seen when completely thawed represent the intracellular fluid that has escaped due to damage to the cell wall.
The low temperature also ensures maximum damage by concentrating the electrolytes intracellularly.
Keratinocytes need to be frozen at -50 ° C for optimal destruction. The melanocytes are more delicate and only require a temperature of -5 ° C for their destruction.
This fact is why the resulting hypopigmentation after cryotherapy in darker-skinned individuals. Malignant skin cancers usually require a temperature of -50 ° C, whereas benign lesions only require a temperature of -20 ° C to -25 ° C.
The last response to cryotherapy is inflammation, which is usually observed as erythema and edema. Inflammation is the response to cell death and helps local cell destruction.
Modalities of treatment with cryotherapy.
Various methods have been devised in the use of cryotherapy for injuries. They include the freezing technique by sprinkling, the applicator method, the cryoprobe method, and the Thermo compressor method.
Liquid nitrogen is the best and most universal source of freezing due to its low boiling point and ease of use. Other sources are used to freeze, such as freon, carbon dioxide, and nitrous oxide, but they are not as efficient at destroying lesions due to their higher boiling points.
Before the freezing of the injury, the patient must be informed of the procedure, and verbal or written consent must be obtained. A local anesthetic, such as 1% lidocaine, or a topical anesthetic, such as ELA-Max (Ferndale Pharmaceuticals) or EMLA (Astra Pharmaceuticals), can be used.