Squamous Cell Carcinoma Following Photodynamic Therapy for Cutaneous Bowen's Disease in a Series of 105 Patients.

Photodynamic therapy (PDT) is an alternative to surgery for Bowen's disease. This monocentric retrospective study included 105 patients with Bowen's disease, treated with PDT between 2007 and 2013, who received a total of 151 different PDT fields. Comparison of immunocompromised and non-immunocompromised patients revealed that the former often had a previous history of squamous cell carcinoma (SCC; p = 0.004) and received more PDT fields (p = 0.007) than the latter. At least one SCC occurred post-PDT in 16 out of 105 patients in a PDT field. However, many of the patients were at risk of SCC and the possibility that the lesion did not have a mixed histology at baseline, but might simply be a transformation of non-PDT-responsive Bowen's disease, cannot be excluded. Although it is rare, patients should be closely monitored for SCC post-PDT.