Photodynamic therapy (PDT) involves the use of photochemical reactions mediated through the interaction of photosensitizing agents, light, and oxygen for the treatment of superficial Basal Cell Carcinoma. It is especially useful for larger superficial Basal Cell Carcinomas on the face and scalp.
Cancerous cells accumulate more light-absorbing cells (porphyrins) than normal cells that when exposed to certain light wavelengths potentiates a beneficial chemical reaction. It is this principle that underpins the use of PDT for such tissues.
The treatment selectively destroys Basal Cell Carcinomas while causing minimal damage to surrounding normal tissue. A biopsy is usually needed to confirm the diagnosis prior.
PhotoDynamic Therapy Treatment Process - Photodynamic therapy is a 2-Step Procedure.
- The First Step:
involves the application to the target growths cells with a photosensitizer in the form of a chemical agent that reacts to light such as Aminolevulinic Acid (ALA) or methyl aminolevulinate (MAL). Curettage is needed to destroy epidermis to allow egress of sensitising cream into lesion for 1 hour under occlusion
- The Second Step:
involves the activation of the photosensitizer in the presence of oxygen with a specific wavelength of light directed toward the target tissue. The photosensitizer is preferentially absorbed by cells that are dividing (which occurs at a greater rate in Actinic Keratoses) and when the light source is directed to the affected areas of skin. This leads to activation of protoporphyrins and inflammation and destruction of the lesion.
Photodynamic therapy achieves dual selectivity with minimal damage to adjacent healthy structures. It is repeated a week later.
It may not be suitable for all patients with BCC’s. The process is invasive and can be very painful when the light is applied and for a day post-treatment, and the curettage will scar.
The approach offers less scarring than surgical excision, and is more suited to larger superficial lesions than surgery, and can be used as a field treatment for areas with multiple small Basal Cell Carcinomas. Success rates are highly operator dependent.
Common side effects are redness, pain, bleeding, and swelling.
PhotoDynamic Therapy Treatment Recovery - After treatment, patients become locally photosensitive for 48 hours where the light-sensitizing agent was applied, and must avoid both outdoor and indoor light and be careful to use sun protection.
PhotoDynamic Therapy Treatment Prognosis - 70-80% cure rate. Can mask the presence of residual disease and so delay successful treatment so an initial biopsy is strongly advised to assess the invasive potential of any Basal Cell Carcinoma prior to PDT being commenced.
Recurrence rates vary considerably (from 0 to 52%), so the technique is not currently recommended for invasive Basal Cell Carcinoma.