Prognostic Factors for Treatment Failure of Photodynamic Therapy and 5-Fluorouracil in Bowen's Disease

Little is known about prognostic factors that may influence the response to non-invasive treatments of patients with Bowen's disease. The aim of this study was to identify patient and lesion characteristics that are associated with a higher risk of treatment failure after 5-fluorouracil and photodynamic therapy in Bowen's disease. The hypothesis that the thickness of the Bowen's lesion and extension along the hair follicle is associated with the risk of treatment failure after noninvasive treatment was also explored.

Data were derived from a non-inferiority randomized trial in which 169 patients were treated with 5% 5-fluorouracil cream twice daily for 4 weeks or 2 sessions of methylaminolevulinate photodynamic therapy with 1-week interval. All patients had histologically confirmed Bowen's disease of 4-40 mm. The initial 3 mm biopsy specimens were re-examined to measure the maximum histological lesion thickness and extension along the hair follicle. To evaluate the association between potential risk factors for treatment failure at 1-year follow-up, univariate and multivariate logistic regression analyses were used to calculate odds ratios (ORs) with 95% confidence intervals and p values.

Histological lesion thickness was not significantly associated with treatment failure (OR: 0.84, p = 0.806), nor was involvement of the hair follicle (OR: 1.12, p = 0.813). Lesion diameter was the only risk factor that was significantly associated with 1-year risk of treatment failure (OR = 1.08 per mm increase, p = 0.021). When using the median value of 10 mm as cut-off point, the risk of treatment failure was 23.4% for lesions >10 mm compared to 10.3% for lesions ≤10 mm (OR: 2.66, p = 0.028).

Only clinical lesion diameter was identified as a prognostic factor for response to non-invasive therapy in Bowen's disease.