Laser-assisted photodynamic therapy

Characteristics

The aim of photodynamic therapy (PDT) is to destroy selected cell structures, mainly in cancer, pre-cancerous conditions (solar keratosis), bacterial (acne vulgaris), viral (condyloma acuminatum) and fungal (onychomycosis) diseases. The mechanism of action of PTD exploits the sensitivity of photosensitising substances to light - the selected substance is applied to the skin and then irradiated. The light-activated dye produces reactive oxygen species that destroy the pathologically altered cells through photo-oxidation. In selected cases, the therapy can be laser-assisted, meaning that the lesions are treated with laser therapy prior to treatment in order to increase the absorption and effectiveness of the photosensitising substance.

The photodynamic method allows for the selective destruction of pathologically altered tissue, is a low-invasive treatment that is well tolerated by patients and allows for good cosmetic results, which is important especially for lesions located in visible areas, such as on the face. The combination of PDT with laser therapy maximises the results of the treatment and shortens its time.

Indications

Laser-assisted photodynamic therapy is used for a wide range of skin diseases, particularly those with bacterial, fungal and cancerous causes. The most common ones are listed below, but it is important to note that it is the doctor who decides whether the patient is eligible for a particular therapy. Treatment may also be used in dermatoses not listed below.

• pre-cancerous conditions such as solar keratosis and post-sun inflammation of the lips
• basal cell carcinoma
• squamous cell carcinoma
• bowen disease
• kaposi's sarcoma
• cutaneous lymphoma
• malignant melanoma
• condylomas
• acne vulgaris
• onychomycosis
• precancerous conditions of the oral cavity, including leukoplakia

Technology

The photosensitising substance used in PDT is a dye that activates when exposed to light of the appropriate wavelength. It has the ability to accumulate in the diseased tissue and destroy selected structures by apoptosis or necrosis with minimal exposure of healthy cells. When exposed to light, the dye reacts with oxygen present in the tissues, leading to the production of singlet oxygen and free radicals that annihilate selected cells. After treatment, the substance is naturally excreted by the body. In dermatology, topical photosensitisers are used, while in the treatment of deeper tissues, substances can be applied orally and intravenously. The most important photosensitisers include porphyrins, chlorins, phthalocyanines and texaphyrins, and the most commonly used photosensitising substance is delta-aminolevulinic acid (ALA).

The absorbability of a variety of substances applied to lesions, including photosensitisers, is limited by the stratum corneum and ranges from 1 to 5 per cent. This problem has always been a challenge in medicine and for this reason methods have been developed to facilitate the penetration of selected topical agents. One of these is laser assistance using an ablative fractional laser. With this technique, perpendicular microchannels called microthermal treatment zones (MTZs) are created in the skin. When the micro-damage to the skin is done before the photosensitiser is applied, it has a chance to penetrate deeper tissue layers and thus act more effectively.

Course of treatment

Each treatment is preceded by a thorough interview with the patient, during which the therapy is discussed, its plan and contraindications to its implementation are excluded. The specialist cleans and disinfects the treatment area, applies an anaesthetic and adjusts the laser parameters. The treated area is then subjected to laser therapy so that microchannels of the appropriate size and depth are created to increase the effectiveness of the photosensitiser used. The doctor applies a dedicated photosensitiser to the treatment area and, if necessary, removes part of the lesion mechanically with tweezers or chemically with salicylic oil before application. The healthy skin around the lesion is covered with a zinc paste. The photosensitised treatment area is then covered with an occlusive dressing for a specific period of time (from 30 minutes for thin skin to 2-3 hours for thick skin). The specialist adjusts the parameters of the lamp and the lesions are irradiated - the treatment time varies according to the problem being treated.

Effects

The results of laser-assisted photodynamic therapy include a variety of effects, depending on the dermatosis being treated. In each case, thanks to the better absorption of the photosensitiser and its even distribution, the patient can expect an increase in its efficacy. Depending on the disease being treated, the following results are observed:

• the possibility of curing pre-neoplastic conditions and skin cancers, depending on their exact specificity,
• cure or reduction of symptoms of bacterial diseases such as acne vulgaris,
• the possibility of curing pre-neoplastic conditions,
• cure or reduction of symptoms of diseases with a fungal basis, such as onychomycosis,
• cure or reduction of symptoms of viral diseases such as condyloma acuminatum.

For full results, it is essential to follow the treatment plan, which is determined individually for each patient depending on the problem being treated, individual conditions and other factors

Preparation for the treatment

At least one month before the treatment, sunbathing and exfoliating treatments (e.g. chemical peels) should be abandoned. Several weeks before the therapy, aesthetic medicine treatments such as botulinum toxin injections or microdermabrasion should not be used. During this time, the patient should also stop using cosmetics, medicines and photosensitising herbs (e.g. chamomile or nettle) and do not use acids. Two weeks before the treatment, smoking should be given up, and on the day of the treatment, no alcohol should be consumed and no moisturisers, lubricants or perfumes should be applied to the skin.

Post-treatment indications

• If the treatment was performed on the face, no make-up should be applied until the skin has healed.
• No soothing or protective creams should be applied until the scabs fall off.
• Patients should avoid sunbathing for a minimum of one month prior to treatment and apply the highest sun protection to the post-treatment area for at least four months after treatment.
• Agents that could dilate blood vessels, such as alcohol or aspirin, should be avoided for about a week after laser therapy.
• Activities that could overheat the skin such as physical activity and swimming pool and sauna should be avoided for 7-14 days after the treatment.
• The skin after the procedure should be treated gently, flaky skin and scabs should not be ripped or scraped off.
• The patient should follow the post-treatment area care instructions set by the doctor.
• Factors that could potentially influence the appearance of infection should be avoided.

Recuperation

Recovery time depends on the problem being treated, the Patient's conditions and many other factors. Immediately after the treatment, the Patient may feel warmth in the treated area. The skin is reddened, irritated and slightly swollen. Peeling of the epidermis and the formation of scabs may occur. These symptoms are natural and resolve within a few hours or days. Local hypersensitivity to light may persist for 48 hours. Full recovery takes about a week, while skin peeling should subside within 2 weeks. If a scab appears on the treated area, it should fall off spontaneously after a few/some days.

Contraindications

• Pregnancy and breastfeeding period
• Photophobia and allergy to light
• Epilepsy
• Implanted pacemaker
• Vitiligo
• Taking anticoagulants
• Certain autoimmune and chronic diseases
• Acute inflammatory skin conditions
• Pharmacotherapy including treatment with vitamin A derivatives

After the consultation, the doctor decides whether the contraindications are an absolute obstacle to the procedure.

The effects of the treatment may vary between patients and depend on many factors, including individual conditions, health, type, size, location and age of the scar and adherence to post-treatment recommendations.

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