Prospective Trial Confirms ALA-PDT Effectiveness for Chinese Patients with Bowen’s Disease

Bowen’s disease (BD), an intraepidermal form of cutaneous squamous cell carcinoma in situ, most commonly occurs on sun-exposed skin in older adults. Although the condition typically progresses slowly, untreated lesions may develop into invasive squamous cell carcinoma in approximately 3% to 5% of cases, highlighting the importance of early treatment.¹

Thus, investigators recently conducted a multicenter, prospective clinical study evaluating the efficacy and safety of 5-aminolevulinic acid–based photodynamic therapy (ALA-PDT) for BD in Chinese patients.²

Background

Surgical excision remains the most common BD treatment in China; however, surgery may lead to pain, infection, scarring, and cosmetic concerns, particularly when lesions are large, multiple, or located in cosmetically sensitive areas. Photodynamic therapy (PDT) has emerged as a noninvasive alternative that can selectively destroy tumor cells while preserving surrounding tissue. While the efficacy of 5-aminolevulinic acid–based PDT (ALA-PDT) has been well established in predominantly Caucasian populations, data on its effectiveness in Asian patients have been limited.

Study Design & Protocol

The trial was performed at 7 tertiary hospitals across China between April 2019 and April 2021. A total of 35 adult patients with histopathologically confirmed BD were enrolled, representing 44 individual lesions. Participants had a mean age of 73 years, reflecting the typical demographic profile of BD. Most patients (88.5%) had a single lesion, while a small proportion presented with multiple lesions. Lesion sizes varied considerably, with an average area of 4.58 cm², and lesions were distributed across both low-risk and high-risk anatomical sites, including the trunk, extremities, head, neck, hands, feet, and anogenital region.

All participants received topical ALA-PDT according to a standardized protocol. Prior to treatment, lesion surfaces were prepared by removing scales and crusts to improve photosensitizer penetration. A 20% 5-aminolevulinic acid gel or solution was then applied to the lesion and extended approximately 1 cm beyond the lesion margins. The treated area was occluded and incubated for 3 to 4 hours to allow sufficient accumulation of protoporphyrin IX, the active photosensitizing compound generated from ALA.

Following incubation, photodynamic fluorescence diagnosis was performed using a handheld light source to visualize protoporphyrin IX accumulation. All lesions demonstrated characteristic brick-red fluorescence, confirming selective uptake of the photosensitizer. Subsequently, lesions were illuminated with 635-nm red LED light at an energy density of 80–120 J/cm². Red light was selected because of its deeper tissue penetration compared with shorter wavelengths. Patients were reassessed every 7 to 14 days, and additional treatments were administered depending on the clinical response. Across the cohort, patients received between 3 and 6 treatment sessions.

Trial Results

The primary study endpoint was the complete response rate three months after the final treatment. Complete response was defined as the disappearance of the lesion with only residual pigmentation or hypopigmentation remaining. At 3 months, the patient-level complete response rate was 97.1% (34 of 35 patients), while the lesion-level complete response rate was 97.7% (43 of 44 lesions). These results demonstrate a high level of treatment effectiveness.

Subgroup analyses evaluated whether demographic or clinical factors influenced treatment outcomes. Variables examined included sex, age, lesion number, lesion size, and lesion location. None of these factors significantly affected treatment response. Recurrence rates were assessed during a 12-month follow-up period. Of the 33 patients available for follow-up, only one experienced recurrence, corresponding to a recurrence rate of 3.0%. This rate is comparable to recurrence rates reported following surgical excision in previous studies, suggesting that ALA-PDT provides durable disease control.³

Cosmetic outcomes were another key secondary endpoint. Physicians evaluated cosmetic appearance at 12 months using a standardized grading system. Overall, 93.1% of treated lesions were rated as having excellent or good cosmetic outcomes, with minimal erythema or pigmentation changes and little to no scarring. These findings highlight an important advantage of PDT over surgical interventions, particularly in cosmetically sensitive areas.

Safety and Satisfaction

Patient satisfaction was similarly high. At 12 months, 92.6% of participants reported being satisfied or very satisfied with treatment outcomes. High satisfaction likely reflects both the favorable cosmetic results and the minimally invasive nature of the procedure.

Safety and tolerability were also assessed throughout the study. The most commonly reported adverse event was mild to moderate pain during illumination, experienced by all patients. Pain intensity peaked within the first few minutes of treatment but gradually declined as the session progressed. The mean visual analog scale (VAS) pain score was 4.56 at 3 minutes after treatment initiation, decreasing to 2.61 five minutes after treatment completion. Other adverse effects included transient erythema (66.7%), itching (27.7%), and occasional pigmentation changes (2.8%). These reactions were generally mild and resolved spontaneously. Importantly, no systemic photosensitivity reactions were observed, and no patients discontinued treatment because of adverse events.

Conclusion

Overall, this multicenter prospective study demonstrates that ALA-PDT is a highly effective and well-tolerated treatment for BD in Chinese patients. Although the study was limited by a relatively small sample size and lack of a control group, the findings provide valuable prospective evidence supporting the use of ALA-PDT as an alternative to surgical excision in BD. Larger controlled studies will be needed to further refine treatment protocols and confirm these results in broader patient populations.

References

1. Xue WL, Ruan JQ, Liu HY, He HX. Efficacy of Photodynamic Therapy for the Treatment of Bowen's Disease: A Meta-Analysis of Randomized Controlled Trials. Dermatology. 2022;238(3):542-550. doi:10.1159/000519319

2. Ran M, Tang Y, Wu W, Wan M, Zhang L, Zhang J, Xue S, Li H. 5-Aminolevulinic Acid–Based Photodynamic Therapy (ALA-PDT) for Bowen’s Disease in Chinese Patients: A Multicenter Prospective Study, Dermatologic Therapy, 2026, 9662750, 8 pages, 2026. https://doi.org/10.1155/dth/9662750

3. Fang S, Zhang L, Wang P, et al. Real-world data of 5-aminolaevulinic acid-mediated photodynamic therapy for Bowen disease: a 10-year retrospective study in patients with darker-coloured skin (2011-2021). Clin Exp Dermatol. 2024;49(10):1190-1196. doi:10.1093/ced/llae139