Important factors for pain during photodynamic therapy for actinic keratosis.

Photodynamic therapy (PDT) is an efficient treatment for actinic keratosis. A common problem, however, is pain. The aim of this study was to investigate pain during PDT for actinic keratosis. The possibility of using capsaicin cream for pain relief was also assessed. Pain was investigated during aminolaevulinic acid PDT in 91 patients. Size, redness, scaling and induration of the lesions were recorded. Maximum pain during treatment was registered, using a visual analogue scale (0-10). The pain-reducing efficacy of capsaicin was tested in a pilot study in six patients (10 lesions). These patients were pre-treated with capsaicin cream for one week before commencing PDT. Pain was found to be normally distributed around a mean value of visual analogue scale 4.6. Larger lesions gave more pain (p=0.001). The redness of the actinic lesions was found to be related to PDT-induced pain (p=0.01), the reduction of actinic area (p=0.007), and the cure rate (p=0.01). The redder the actinic area, the better the treatment outcome and the more pain experienced. Patients with the largest reduction in the actinic area experienced more pain (p=0.053). The most important factors for presence of pain seem to be the size and the redness of the lesion. No significant pain relief was experienced after pre-treatment with capsaicin.