Photodynamic Therapy Benefits

Photodynamic therapy (PDT) is a method of treating tumors with light in combination with a light-activatable substance called a photosensitizer.

Indications (areas of application)

Actinic keratosis – light keratosis

An actinic keratosis is a cornification disorder of the skin. It is caused by solar radiation – or solarium – and therefore occurs especially in people who are frequently exposed to this radiation. The change occurs especially on the face, neck and the back of the hands, i.e. in areas that are usually exposed to the sun without protection. As a rule, older people are more likely to be affected, men more often than women. The keratoses are initially recognizable as slightly reddish, dry areas. Over time, these areas thicken, are raised, yellowish-brown in color, and dry-scaly. In the case of individual foci, surgical removal may be indicated beforehand. This can also be done by cryotherapy or CO2 laser therapy. This approach has proven effective as a pretreatment to photodynamic therapy (PDT) on the arms and legs, as it enhances the subsequent formation of protoporphyrin IX (PpIX). Notice: In some cases, actinic keratosis can develop into cancer – called squamous cell carcinoma of the skin. Therefore, actinic keratoses are also referred to as precancerous lesions (precancerous lesions).

Basal cell carcinoma

The skin consists of several layers. The lowest layer of skin, from which the new skin cells grow upward, is called the basal cell layer. In it lie the so-called basal cells, which are diseased in basal cell carcinoma. If the cancer lies in the next skin layer, it is called squamous cell carcinoma of the skin (spinocellular carcinoma; formerly: spinalioma, prickle cell carcinoma). Basal cell carcinoma causes changes in the skin similar to eczema, scars or nodules. The cancer grows very slowly, but can still spread to deeper tissues, such as bone. By means of photodynamic therapy, basal cell carcinomas or precancerous lesions (actinic keratosis) can be selectively treated at an early stage in a gentle manner in order to prevent the disease from spreading.A major advantage of photodynamic therapy compared to surgical interventions is the fact that usually no visible scars remain. Furthermore, there is significantly less pain than with other treatment methods. Should the disease recur, it can be treated again using PDT. Note!In the meantime, this procedure is used for numerous other dermatological indications, such as Bowen’s disease and verruca vulgaris (warts).

Bowen’s disease

In Bowen disease (synonyms: Bowen-Darier disease; Bowen-Darier syndrome; Bowen dermatosis; Bowen dermatosis, Bowenoid precancerosis, dermatosis praecancerosa Bowen, Bowen carcinoma; Bowen epithelioma; Bowen disease; erythroplasia quéyrat; ICD-10 D04.-) is a skin disorder that belongs to the precancerous (precancerous) group. It is called intraepidermal carcinoma in situ and is considered a precancerous stage of squamous cell carcinoma (spinocellular carcinoma; formerly spinalioma, prickle cell carcinoma). Histologically, Bowen’s disease is an intradermal carcinoma.If this precancerous lesion is located in the mucosal area, it is referred to as erythroplasia quéyrat. In the long term, Bowen’s disease develops into an invasive squamous cell carcinoma (Bowen’s carcinoma, in about 30-50% of patients). Bowen’s carcinoma can metastasize lymphogenically. Later on, distant metastasis (spread of tumor cells from the site of origin via the blood/lymphatic system to a distant site in the body and growth of new tumor tissue there) is also possible.In about one-third of cases, erythroplasia queyrate progresses to invasive spinocellular carcinoma (squamous cell carcinoma).

Nononcologic indications

  • Acne

In acne patients, photodynamic therapy is used to selectively destroy (destroy) the sebaceous glands to reduce increased sebum (sebum) production.In addition, a peeling effect is produced, which counteracts the hyperproliferation of the follicular epithelium, and has an antibacterial effect.Very good treatment success was shown by the use of the photosensitizer aminolevulinic acid (ALA) and red light or flash lamp, as well as indole-3-acetic acid (IES) and green light. Patients with acne conglobata (most severe form of acne vulgaris associated with severe inflammation and subsequent scarring) show good efficacy of ALA combined with red light.

Before treatment

  • Photodynamic therapy is preceded by physical treatment of the skin, i.e., keratinized skin areas are removed using an ablative fractional laser (AFXL), microdermabrasion (with special pads), microneedling, or a curette.Note: The highest accumulation of photosensitizer was achieved after AFXL, with a median of 8861 AU (AU: arbitrary units). This was followed at similar levels by microdermabrasion (6731 AU), microneedling (5609 AU) and curettage (4765 AU).

The procedure

The affected areas of the skin are pretreated with a cream containing the photosensitizer MAOP (methyl 5-amino-4-oxo-pentanoate). The cream is protected by a bandage so that it can penetrate the skin well and remains on the skin for about three hours. During this time, the photosensitizer accumulates in the diseased tissue and leads to the formation of porphyrins there. Porphyrins act as a cell poison because they are photoactive. This means that under the influence of red cold light, porphyrins form oxygen radicals (aggressive oxygen) by transferring the energy of the supplied light to the oxygen. This process leads to the death of the diseased cells.Healthy cells are not affected by this procedure, because the photosensitizer is selectively enriched only in the tumor tissue. Following the treatment, it is important to protect the skin from sunlight for 24 hours. Usually, about one to two treatments are necessary, each lasting only about 10 minutes. Instead of illumination with red cold light (red light PDT), photodynamic therapy with daylight (DLPDT) can be used as an alternative. This approach is referred to as daylight PDT. According to a study in patients with multiple actinic keratosis, daylight PDT is clearly superior to conventional PDT in terms of tolerability and patient satisfaction, with similarly high response rates: 70% with daylight versus 74% with the conventional method (c-PDT). Similarly, adverse effects on treated lesions occurred less frequently with daylight PDT (45.4 versus 61.1%).Among the major advantages of daylight PDT is the near absence of pain!

Potential complications

  • Classic conventional PDT
    • Pain – 95% of patients treated during irradiation with classical conventional PDT experienced pain of varying intensity.
    • Erythema (skin redness) and edema (swelling) – second most common side effect at 90%; occurrence about half an hour after PDT and persistence on average one week
    • Postinflammatory desquamation (scaling after inflammation) – in 82% of patients 48 to 42 hours after irradiation.
    • Crusting – occurrence in Bowen’s disease or extensive basal cell carcinoma, as well as in larger areas in patients with field carcinomatization (confluence of individual actinic keratosis).
    • Pustules (formation of pustules) – in 14% of patients (pustules/pustules are sterile and are considered to be a consequence of the phototoxic reaction on the follicle)
    • Hypo- and hyperpigmentation (decreased and increased pigmentation, respectively) – during irradiation of solid tumors (basal cell carcinomas), due togreater penetration depth of irradiation.
    • Superinfections (overgrowth with bacteria, fungi, etc.; 0.5%) – most likely due to cats because of itching.
  • Daylight PDT
    • Pain is almost completely eliminated
    • Erythema, edema, pustulation, scaling – almost similar to classic conventional PDT.
    • If photoprotectants are forgotten, severe sunburn and severe phototoxic reaction may occur.

Other tips

  • In patients with actinic keratosis on the face or scalp, a study compared curative days before daylight PDT versus daylight PDT alone with prolonged methyl aminolevulinate (MAL) incubation: comparable cure rates as well as side effects of PDT were seen.