What is hyperkeratosis?
Hyperkeratoses are classified as actinic hyperkeratosis or as seborrheic hyperkeratosis. The former are pre-cancerous skin lesions and they appear on sun exposed skin, whereas the latter are deposits of sebum and keratinocytes, which present as slightly bulgy or swollen skin lesions, with an uneven, dark coloured surface. They usually appear in older people.
Photodynamic Therapy for actinic hyperkeratoses
Topical photodynamic therapy with 5-aminolevulinic acid (ALA-PDT) for actinic hyperkeratoses, Bowen’s disease, and surface basal cell epitheliomas.
The topical action of photodynamic therapy is of maximum efficiency regarding hyperkeratosic actinic keratoses on the face and scalp, Bowen’s disease and surface basal cell carcinomas (with a width of up to 2 mm). Some additional interventions so as to remove the keratosic plaques of actinic hyperkeratosis and the nodules of the basal cell carcinomas, allow the use of photodynamic therapy in these cases, too. Photodynamic therapy is not recommended for acanthocytic epithelioma, due to the high rates of re-appearance and the metastatic potential which is characteristic of this.
Special caution should be paid to the areas of the eyelids, nose, lips and genitals, where the absorption of the photosensitizer by the surrounding skin and mucosa, in combination with the oedema that may appear, increase pain during photodynamic therapy.
Preparation of the area of the lesion
Surface crust is removed carefully, so as not to cause haemorrhage, either with a) some gauze soaked in physiological serum or b) by slight abrasion of the lesion with the edge of a lance or c) with the use of an abrasive substance. The surrounding healthy skin is not abraded. For skin preparation no local anaesthesia or sterilization is required; however, protective gloves should be worn. In rather difficult cases, the use of an emollient such as salicylic acid is recommended (e.g. 3-5% salicylic acid in Vaseline) for 1 or 2 weeks prior to the treatment, every night. Alternatively, some hydrocolloid can be applied a couple of days prior to treatment.
The application of the photosensitizer allows coverage of the whole area of the lesion as well as a minimum area of 5 mm around the lesion, with a thin 1-2 mm layer. The photosensitizer may irritate if the skin is wounded.
A special bandage is used in order to confine the photosensitizer within the lesion’s area (e.g. Tegaderm). On rather sensitive areas (e.g. around the eyes) or on areas with intense curves (e.g. around the nose), some extra bandage is applied. It is recommended that during incubation the area is not exposed to light, although this is not compulsory. Aluminium foil or several layers of bandage can be used.
We allow the photosensitizer to be absorbed for at least 3 hours in actinic keratoses and Bowen’s disease or for 6 hours in cases of basal cell carcinomas.
Application of treatment
When the patient returns the bandages are removed, together with the remaining photosensitizer.
Optionally local anaesthesia may be applied after the removal of the photosensitizer or 60 minutes prior to the photodynamic therapy session (i.e. 2-5 hours prior to treatment). Furthermore, it may be necessary to perform a subcutaneous injection around the lesion with local anaesthetic.
Patients should be advised to wear protective glasses in case the lesion is located near their eyes. Moreover, the doctor and nurse can wear dark glasses to avoid any possible irritation by the intense light of therapy. The light as such is not harmful.
Depending on the area of the lesion the patient may remain sited or lie down. The illumination area should exceed the lesion by at least 5 millimetres.