BACKGROUND: Pulse photodynamic therapy (PDT) is carried out as classical PDT except that methyl aminolaevulinate (MAL) is removed after 30 min. Protoporphyrin IX (PpIX) accumulation becomes lower after 3 h in pulse-PDT than in classical PDT, but pulse-PDT still has full treatment effect on actinic keratosis (AK). The present study aimed to investigate when PpIX formation in classical PDT without curettage reaches the PpIX level in pulse-PDT with curettage in the skin of the face and scalp.

METHODS: Fourteen patients with AKs in the face and scalp were included in this pilot study. Each patient had two fields randomly allocated to two different regimes: (i) continuing MAL incubation without prior curettage (-Cur) and (ii) 30 min MAL incubation after curettage (+Cur). The PpIX level in each field was measured with a hand-held fluorescence photometer every 30 min for 6 h after MAL application. No illumination was performed.

RESULTS: The median PpIX level in the +Cur field after 3 h was 22 arbitrary units (AU), which represents the amount of PpIX that could have been photobleached after pulse-PDT with maximal treatment effect. After 3 h the median PpIX level in the -Cur field was 20 AU, which was not significantly different from the level in the +Cur field (p = 0.9).

CONCLUSIONS: We propose PDT without curettage as follows: 3 h of MAL incubation and subsequently sufficient illumination. The treatment effect of this regime should be tested to verify if curettage of the face and scalp area may be omitted in PDT.