Methyl aminolaevulinate photodynamic therapy (MAL-PDT) is an effective treatment for Bowen's disease (BD) of the lower extremities. Er:YAG ablative fractional laser (AFL) treatment removes the stratum corneum to increase MAL uptake and may improve efficacy. However, no studies have directly compared the efficacy of MAL-PDT with and without Er:YAG AFL in treating BD of the lower extremities in Asians.

Bowen's disease (BD) is a form of intraepidermal (in situ) squamous cell carcinoma (SCC) originally described in 1912.1 It presents as a gradually enlarging, well-demarcated erythematous plaque with an irregular border and surface crusting or scaling.2 BD is the frequent precancerous skin lesion in Caucasians.3 In the UK, BD occurrence is most common among patients in their 70s and in women (70-85%), and the majority (60-85%) of cases involve lesions of the lower leg.4,5 BD is estimated to evolve into invasive SCC in 3-5% of cases; therefore, treatment is recommended.6 Current guidelines suggest that the available therapeutic options (including cryotherapy, curettage, excision, topical 5-fluorouracil, and topical imiquimod) are broadly similar in efficacy, with 12-month recurrence rates of approximately 5-10%.7 However, cryotherapy can be painful, making treatment of multiple lesions difficult, and healing can be slow.8 Additionally, topical treatment with 5-fluorouracil or imiquimod is relatively slow and typically causes local irritation.9,10 Photodynamic therapy (PDT) with methyl aminolaevulinate (MAL) is an attractive treatment option for BD with large or multiple patches, and poor healing sites can be treated with good efficacy, low recurrence rates, and good cosmetic outcomes.7 PDT requires light activation of a photosensitizer in the presence of oxygen, which generates reactive oxygen species leading to selective and highly localized destruction of abnormal cells.11,12 MAL is an efficient photosensitizer, with deep lesion penetration resulting from enhanced lipophilicity. Compared to 5-aminolevulinic acid, MAL also has a greater specificity for neoplastic cells.13-15 Because histologic features of BD include full-thickness keratinocyte atypia with disordered maturation, it is typically treated twice within an interval of 1 week.16,17 So, complementary techniques are needed to enhance the penetration and accumulation of MAL in order to improve PDT efficacy and decrease treatment duration.

Er:YAG ablative fractional laser therapy (AFL) can ablate the stratum corneum in a precisely tuned manner without producing significant thermal injury. This approach creates microscopic vertical holes in the ablated tissue, surrounded by thin layers of coagulated tissue.18,19 Since the Er:YAG AFL resurfaces 5-20% of the skin at one time and does not injure the entire thickness of the epidermis, healing times are minimized.18,19 Recent studies have demonstrated that AFL facilitates delivery and uptake of topical MAL deep into the skin, enhancing porphyrin synthesis and photodynamic activation.20,21 The objectives of this study were to compare the efficacy, recurrence rate, cosmetic outcomes, and safety of MAL-PDT with and without the use of Er:YAG AFL in Asian BD patients with multiple lower extremity lesions.

Inclusion Criteria:

• Korean patients aged ≥ 18 years who had biopsy-confirmed BD lesions on the lower extremities

Exclusion Criteria:

• porphyria,
• known allergies to the MAL cream or lidocaine,
• pregnancy,
• lactation,
• any active systemic infectious disease,
• immunosuppressive treatment,
• personal history of malignant melanoma,
• tendency towards melasma or keloid formation,
• prior treatment of the lesions within 4 weeks, and
• any indication of poor compliance