Photodynamic Therapy: Clinical practice guideline for dermatologists

The British Association of Dermatologists and the British Photodermatology Group have released guideline on topical photodynamic therapy (PDT).

Photodynamic therapy involves the use of photochemical reactions mediated through the interaction of photosensitizing agents, light, and oxygen for the treatment of malignant or benign diseases. Photodynamic therapy is a 2-step procedure. In the first step, the photosensitizer is administered to the patient by one of several routes (eg, topical, oral, intravenous), and it is allowed to be taken up by the target cells. 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 guideline provides an update on photodynamic therapy for the practicing dermatologist by discussing each of the essential components in sequence: mechanisms of action, common photosensitizers, typical light sources, and applications. Although various photodynamic therapy photosensitizers have been studied in dermatology, this article focuses on the uses of topically applied aminolevulinic acid (ALA) and methylaminolevulinate (MAL).

Basal Cell Carcinoma

• Topical PDT should be offered as a treatment option for superficial basal cell carcinoma (BCC), in particular for skin sites that are healing poorly or are cosmetically sensitive, in cases with multiple lesions, and in lesions that cover a large area.


• Topical PDT can be considered for thin (<2 mm) nodular BCC in situations in which other treatments are impractical or contraindicated.


• Further cycles of PDT can be given for residual lesions when a good response was achieved with prior treatment.


• Topical PDT should not be offered as a standard treatment for nodular BCC at high‐risk sites.


• For enhanced penetration for BCC, use red light and not light of a shorter wavelength (eg, blue light, green light, daylight).

Squamous Cell Carcinoma in situ (Bowen Disease)

• Topical PDT should be offered as a treatment option for squamous cell carcinoma (SCC) in situ, in particular for skin sites that are healing poorly or are cosmetically sensitive, in cases with multiple lesions, and in lesions that cover a large area.

Actinic Keratosis

• Topical PDT should be offered as a treatment option for actinic keratosis, in particular for skin sites that are cosmetically sensitive, in cases with multiple lesions, and in lesions that cover a large area.


• Further cycles of PDT can be given for residual lesions when a good response was achieved with prior treatment.


• Daylight topical PDT can be considered for mild (slightly palpable lesions, more easily felt than seen; Olsen grade I) or moderate (moderately thick lesions, easily felt; Olsen grade II) lesions when pain is likely, in particular for confluent areas on the scalp or face.


• Combination treatment with topical PDT and other modalities (eg, imiquimod, pretreatment with an ablative fractional laser) can be considered, if appropriate, for people with thick actinic keratoses (very thick or obvious lesions; Olsen grade III).

Squamous Cell Carcinoma

• Topical PDT can be considered as a treatment option in microinvasive SCC if surgery is contraindicated.


• Topical PDT should not be offered for invasive SCC.

Skin Cancer Prophylaxis

• Topical PDT can be considered for prophylaxis to reduce the development of new lesions in patients with actinic keratosis or nonmelanoma skin cancer, including individuals who have undergone organ transplantation.

Vulval Intraepithelial Neoplasia

• Topical PDT can be considered for lesions of vulval intraepithelial neoplasia that are (1) unifocal, (2) nonpigmented, (3) without associated human papillomavirus infection, and (4) with lower grades of dysplasia.

Erythroplasia of Queyrat

• Topical PDT can be considered in erythroplasia of Queyrat (Bowen disease of the glans penis); however, pain may be a limiting factor.

Cutaneous T‐Cell Lymphoma

• Topical PDT can be considered for cutaneous T-cell lymphoma, in particular for early‐stage disease, cases with few localized lesions, and those in challenging sites (eg, skinfolds).

Extramammary Paget Disease

• Topical PDT can be considered for extramammary Paget disease with thin or small lesions in situations in which (1) the Paget cell infiltrate is less dense and (2) there is limited adnexal involvement.


• Topical PDT can be considered for extramammary Paget disease either before or after surgery.


• An additional treatment option to be considered for extramammary Paget disease is carbon dioxide laser treatment prior to topical PDT.

Acne

Topical PDT can be considered for acne if standard treatments are ineffective or contraindicated.

Antimicrobial Treatment for Cutaneous Leishmaniasis, Fungal Infections, or Viral Warts

• Conventional PDT can be considered for cutaneous leishmaniasis, in particular for cosmetically sensitive skin sites. Daylight PDT can also be considered for cutaneous leishmaniasis; however, several treatments may be required.


• Topical PDT can be considered for recalcitrant viral warts.


• Topical PDT should not be offered as a treatment option for fungal infections.

Psoriasis

• Topical PDT should not be offered as a treatment option for psoriasis.

Actinic Cheilitis

• Topical PDT can be considered for actinic cheilitis.