Photodynamic therapy, a new curative and preventive treatment for non-melanoma skin cancer, has important advantages over alternatives such as surgery, said dermatologist Laura Alfie, who said that 92 percent of patients are cured.
There are many patients who have been exposed to the sun for a long time and who have received so much radiation have chronic photodamage on the skin of the face, chest, torso or hands, where they see keratosis or pink spots that are very common and in some precancerous cases, explained the specialist to the news agency.
Member of the Argentina Laser and Medical Technology and Argentina of Dermatology societies, Alfie said that although the technology was approved in the country in 2007 and is applied in the United States and Europe, there are very few doctors who recommend it due to lack of information. .
The problems are not installer, the treatment on your skin what is important is to have good information. And it is a therapy that combines drugs in creams for skin cancer and light technology, the truth is that it gives excellent results.
The specialist explained that if the patient presents a single cancerous lesion, surgery is suggested, but that when the lesions cover wider spaces and involve a large amount of damaged skin, this therapy appears as a solution.
It acts with a photosensitizing medicine that is applied in the form of a cream for a period of three hours, to penetrate the DNA of the damaged cell, and then the area is illuminated with a special lamp of 630 nanometers, that is, with a wave length Special that activates the cream and destroys the diseased cells, leaving intact the healthy tissue that surrounds them and without leaving scars, detailed.
After lighting, it is recommended to keep the treated area clean and dry and take care for two days with sunscreen, which should be renewed every two hours if there is exposure to light.
MECHANISM OF ACTION
The basic principle of the mechanism of action of photodynamic therapy is the photooxidation of biological materials in certain tissues. The mechanism of photodynamic cell damage, with the protoporphyrin of the endogenous synthesis of amine-aminolevulinic acid, involves complex interactions between visible light photons, the photosensitizer located in the tumor tissue, molecular oxygen, certain intracellular eliminators of different reactive species of oxygen and various cellular processes. repair. Therefore, the simultaneous interaction between a photosensitive agent and the appropriate wavelength light with the presence of oxygen is required.
Decreases and effects have been demonstrated in photodynamic therapies with low oxygen concentrations and the effect of tissue treatment with hypoxemia. Several studies suggest that in hypoxia areas tumors do not respond in the same way to photodynamic therapy.
To perform the endogenous photosensitization of the tumor tissue, a precursor of the photosensitizer is applied, in this case 5-aminolevulinic acid (ALA), which is localized and metabolized preferably to protoporphyrin IX (PpIX) by certain cells or tissues. When PpIX is irradiated, it is activated, that is, it is transformed into an excited photosensitizer that tends to return to a stable state by combining the transfer of electrons and energies, resulting in the formation of oxygen free radicals: super anion oxide and hydroxyl. radical.
These radicals act selectively in the tissues where the photosensitizer is found (for example: hyperproliferative keratinocytes and sebaceous glands), which causes necrosis by coagulation, induction of apoptosis, microthrombosis of newly formed tumor vessels and intense inflammation of the affected area, due to the release of vasoactive and procoagulant factors (platelet activation factor and thromboxane A2).
Most cells in the human body can transform 5-aminolevulinic acid (ALA) or methylaminolevulinic acid (MAL) into porphyrins. For example, damaged and highly proliferative epidermal cells produce more PpIX when exposed to ALA and light, perhaps as a result of an alteration in the barrier function that allows a greater penetration of the photosensitizing substance.
The knowledge that neoplastic cells accumulate more porphyrins than healthy cells complements the development of therapeutic modalities for actinic keratosis, this disease called Bowen and carcinoma, basal cells with photodynamic therapy. In the topic of acne, the preferential accumulations of porphyrins in the sebaceous gland and the decrease of P. Acne accumulates porphyrins in natural, blue or red light, only because it may have more direct photodynamic therapeutic effects.
Beyond the direct phototoxic effect on target tissues, photodynamic therapy modifies the expression of cytokines and induces specific immune responses.
The first photosensitive substances applied in photodynamic therapy were compounds derived from the intravenous administration of hematoporphyrin. The main disadvantage was its slow elimination, so patients could have photosensitivity reactions until 6 to 10 weeks after the end of treatment. With the need to develop compounds that had light absorption for more than 630 nm, the second generation of photosensitizers emerged, which increased the penetration capacity of the tissue, the photodynamic effect and the speed of elimination of the white tissue.
The topical application of 5-aminolevulinic acid marked the starting point for photodynamic therapy in the field of dermatology. This compound, by itself, is not photosensitizing, but after its administration it is converted into protoporphyrin IX (PpIX), which is clinically useful as a photosensitizing agent.6 When PpIX is activated by the light source, it is completely metabolized in 24 a . 48 hours and does not leave residual photosensitivity in the tissues. This is a good advantage, with respect to another substance, this means that it is very important. Also, 5-aminolevulinic acid has rapid tissue clearance, which significantly decreases the potential for phototoxic reactions after treatment, ie, does not cause generalized photosensitivity.