Photodynamic therapy (PDT)

MAL-PDT; ALA-PDT; daylight PDT

PDT uses a topical photosensitiser (methyl aminolaevulinate, MAL, or 5-aminolaevulinic acid, ALA) preferentially taken up by neoplastic keratinocytes, then activated by red light to produce reactive oxygen species and selective tumour cell death. Used for actinic keratosis, Bowen's disease and superficial BCC. Excellent cosmetic outcomes; particularly useful for field treatment and lower-limb sites where wound healing is poor.

CurrentLast reviewed 25 March 2026

Indications

Actinic keratosis — face, scalp, dorsal hand. Excellent for field treatment.
Bowen's disease — first-line for large or lower-limb lesions where surgical wound healing is problematic.
Superficial BCC — well-established alternative to surgery for low-risk lesions.
Thin nodular BCC (≤2 mm) — selected cases.
Field treatment in OTRs — to control widespread actinic damage.

Not suitable for invasive cSCC, pigmented lesions, melanoma, deeply invasive or high-risk BCC.

Standard protocol (MAL-PDT)

Curette / debride hyperkeratosis to optimise photosensitiser penetration.
Apply 1 mm thick layer of MAL cream to the lesion plus 5 mm peripheral margin.
Cover with occlusive dressing for 3 hours.
Wipe off cream; check fluorescence with Wood's lamp (optional).
Illuminate with red light source (Aktilite or equivalent, 630 nm, ~37 J/cm²) for approximately 8 minutes.
Pain during illumination is common — paracetamol pre-treatment, cooling fan, local anaesthetic infiltration if severe.
Repeat after 1 week (BCC, Bowen's) — single session usually sufficient for AK.

Daylight PDT (for AK)

Apply sunscreen (chemical, not physical) to entire field.
Apply MAL.
Patient sits in daylight for 2 hours within 30 minutes of MAL application.
Significantly less painful than conventional PDT.
UK weather permits ~6 months of effective daylight PDT.

Outcomes

AK clearance: ~90% at 3 months; somewhat lower long-term.
Bowen's disease 5-year clearance: ~70–80%.
Superficial BCC 5-year clearance: ~75% (cf. ~90% surgery; comparable to imiquimod).
Excellent cosmesis vs surgery — main reason patients choose PDT.

Contraindications & cautions

Porphyria.
Photosensitivity disorders.
Allergy to MAL or carrier ingredients.
Pigmented lesions (poor light penetration).
Pregnancy — limited data.

Practical

Counsel: pain during illumination; erythema, oedema, crusting for 7–10 days after; transient hyperpigmentation.
Strict sun avoidance for 48 hours after treatment.
Repeat at 3 months for residual / recurrent disease.

References

Morton CA et al. European Dermatology Forum guidelines on topical photodynamic therapy 2019. J Eur Acad Dermatol Venereol; 2019.

Wiegell SR et al. Daylight photodynamic therapy for actinic keratosis. J Am Acad Dermatol; 2012.

Roozeboom MH et al. 5-year outcomes of fractionated PDT versus methyl aminolevulinate cream for superficial BCC. JAMA Dermatol; 2015.