A review of pain experienced during topical photodynamic therapy--our experience in Dundee

Topical photodynamic therapy (PDT) using 5-aminolaevulinic acid (ALA) and its methylated ester, methyl aminolevulinate (MAL) is widely used to treat superficial non-melanoma skin cancer (NMSC). It has been proposed that ALA PDT is more painful than MAL PDT. The aim of this paper was to compare pain scores of MAL PDT with ALA PDT in our patients and to analyse the relationship between various parameters and pain during PDT.

We retrospectively reviewed case notes and electronic records for all patients with superficial NMSC treated with PDT from June 2007 to March 2009.

On univariate analysis of patients with single lesions only, we observed no association between pain and lesion diameter or pro-drug or dose or diagnosis. Pre-treatment PpIX fluorescence was significantly associated with pain. However on univariate analysis of all patients (whether single or multiple lesions) treated with PDT, MAL was associated with significantly less pain than ALA. When all the recorded variables were taken into account (multivariate analysis), diagnosis, pre-treatment PpIX fluorescence and lesion diameter were associated with pain.

Our data lends some support to previous published reports suggesting that the MAL PDT regime is less painful than that for ALA PDT. However, PDT pain is multifactorial and choice of photosensitiser is probably not a major pain determining factor. A prospective randomised study, with the same incubation periods for each pro-drug, is needed to definitively answer the question as to whether or not MAL PDT causes less pain than ALA PDT.