beauty

Photodynamic therapy

What's this

Photodynamic therapy is an innovative technique successfully used in the treatment of diseases and skin disorders of different origin and nature.

Photodynamic therapy is also known as PDT (English acronym for Photo Dynamic Theraphy ) and uses special substances - called photosensitizers - which, to perform their function, must be activated by a light source. As a result of this activation, a photodynamic reaction is established which destroys the malignant cells selectively.

Indications

As mentioned, photodynamic therapy is useful for treating skin disorders and diseases of various origins and nature. This particular technique, in fact, can be used both in the aesthetic field and in the medical field.

In detail, phototherapy is particularly indicated for treating / contrasting:

  • Acne;
  • warts;
  • Skin lesions due to photodamage;
  • Skin aging;
  • Actinic and solar keratosis;
  • Pre-tumor lesions;
  • Tumors (such as squamous cell carcinoma and basal cell carcinoma).

Furthermore, photodynamic therapy can also be used to remove unwanted hair (epilation).

However, it is important to point out that - although it is a treatment that can also be used in the aesthetic field - photodynamic therapy must still be prescribed by the specialist.

In this article, however, the aspects and principles of functioning of the photodynamic therapy applied in the medical-oncological field will be mainly described.

Action mechanism

Before proceeding with the description of the mechanism by which photodynamic therapy explains its action, it is necessary to better understand what photosensitizing substances are.

Photosensitizing substances are substances which, when applied to damaged skin, penetrate and select malignant cells, distinguishing them from healthy ones. Their name is due to the fact that these compounds can only be activated by a particular light irradiation. In fact, if these substances are applied to the damaged epidermal surface without being irradiated by light, photodynamic therapy does not bear fruit.

Of course, light is the common thread of photodynamic therapy, since, without it, therapy would not be effective.

When the area of ​​the body on which the photosensitizing substances have been applied is irradiated by light to a specific wavelength, the aforementioned substances absorb a part of the light radiation with consequent formation of reactive oxygen species (ROS, an acronym deriving from the 'English "Reacting Oxygen Species") that destroy the cells in which they developed.

Since the photosensitizing substances, in the context of photodynamic therapy, are able to distinguish harmful cells from healthy cells, ROS will be formed only in malignant cells, leaving undamaged and undamaged ones intact.

However, a clarification is advisable: oxygen is present in all cells, but evolves in the reactive form (ROS: oxygen peroxide, superoxide anion and singlet oxygen) only when the cell is excited by light.

The photodynamic theory is complex, but very effective and above all painless.

Types of photosensitizers

Before analyzing in detail which are the photosensitizing substances used in photodynamic therapy, it is necessary to specify that, as a rule, the compounds used to combat neoplastic pathological disorders are different from those used for aesthetic purposes. Furthermore, the way in which these substances are administered also differs according to the disorder to be treated.

In patients undergoing photodynamic therapy to treat problems of an aesthetic nature (eg acne, depilation, etc.) or less severe skin diseases and disorders, photosensitizing substances must remain in contact with the skin for a relatively consistent period (2 or 3 hours ), necessary to allow it to penetrate deeply. In more serious cases, on the other hand, the substances are administered intravenously (this procedure is generally carried out for the elimination of neoplasms).

The photosensitizing substances most commonly used for the treatment of neoplastic diseases are hematoporphyrin (HP) and its derivatives. In these cases, as mentioned above, the administration of hematoporphyrin takes place intravenously. In this way, the substance spreads through the blood and manages to reach all the districts; despite this, only the diseased tissues retain it, while healthy cells are able to eliminate it quickly.

Another photosensitizing substance used for medical purposes (oncology and not only) is 5-aminolevulinic acid (5-ALA). The 5-ALA, in truth, is the first compound to take part in the series of reactions that lead to the biosynthesis of porphyrins, so it is a compound that is naturally produced by the cells. However, if it is administered through the skin (via topica) and irradiated with light at a known wavelength, this substance is activated by destroying the abnormal cells.

In addition to the medical field, 5-aminolevulinic acid can also be used to perform photoepilation (therefore in the aesthetic field): in these cases, the target to be eliminated is represented by the hair and the interaction between substance and light energy is the useful means to destroy the follicle.

Below are some examples of drugs used in photodynamic therapy: Foscan - temoporfin; Gliolan - 5-aminolevulinic acid hydrochloride; PhotoBarr - porfimer sodium; Visudyne - verteporfin.

Before treatment

Before undergoing photodynamic therapy, obviously, it is necessary to carry out an accurate dermatological examination, during which the doctor will determine the type of skin lesions to be treated and decide which treatment is best suited to each individual case.

If the doctor agrees to perform photodynamic therapy, the patient should avoid using cosmetic products of any kind in the treated area for the three days prior to the treatment.

The treatment

The actual treatment begins with the administration of the photosensitizing substances chosen by the doctor (intravenously or topically, depending on the case). After that, you can proceed with the irradiation of the area affected by the disorder or pathology.

The light energy used can be different depending on the type of photodynamic therapy: for example, if 5-ALA is used as a photosensitizing substance, the lamps should emit red light at a wavelength of 660 nanometers. The light emission range drops to 630 nanometers when the photosensitizing substance is hematoporphyrin.

In general, the luminous treatment has an average duration of 30 minutes, which represents the time necessary to eliminate imperfections or neoplasms; obviously this duration may vary depending on the severity of the disturbance.

In the first few minutes of treatment, the patient may feel a slight sensation of heat, associated with any pain or burning. These symptoms are attributable to the elimination of damaged or diseased cells. However, if these symptoms occur, it is sufficient to temporarily stop the treatment and resume it as soon as they are attenuated.

To overcome the problem of heat, instead, usually, photodynamic therapy machines are also equipped with special fans.

Depending on the disorder or pathology that has to be treated, it may be necessary to resort to more than one photodynamic therapy session. For example, the lesions caused by actinic keratoses resolve in a single session; for pre-cancerous forms, however, more therapies may be needed.

Side effects

The side effects due to this type of therapy are generally mild and reversible.

Immediately after the treatment and in the following two or three weeks, it is quite common to feel burning, pain or itching in the area that has been treated.

If the pain is particularly intense, the doctor may decide to prescribe the use of pain medication.

Contraindications

Although it is a normally well tolerated treatment, photodynamic therapy is contraindicated in patients suffering from:

  • Light sensitivity;
  • Xeroderma pigmentoso;
  • Porphyria.

Photodynamic therapy is also contraindicated in pregnancy, lactation and in patients under 16 years of age.

Furthermore, this treatment cannot be performed in patients who have undergone retinoic acid based therapies in the previous thirty days.

Limits, Cost and Disadvantages

Photodynamic therapy is an innovative technique, very effective and generally painless, unfortunately, however, it also has some limitations and disadvantages.

One of the main limitations is undoubtedly the cost: the price of drugs and machinery used for the emission of light rays is very high. The technique, besides being very expensive, is decidedly complex and laborious: photodynamic therapy therefore requires specialized personnel and adequate medical facilities.