BACKGROUND: Topical photodynamic therapy (PDT) is an approved treatment for actinic keratosis (AK). To enhance the efficacy of PDT for AKs, physical and chemical pretreatments have been suggested.

OBJECTIVES: To compare the efficacy and safety of the combination of topical calcipotriol (CAL) before methyl aminolaevulinate (MAL)-PDT for AKs of the scalp vs. conventional MAL-PDT in a randomized controlled clinical trial.

METHODS: Twenty patients with multiple AKs on the scalp were randomized to receive conventional MAL-PDT with previous curettage on one side of the scalp and CAL-assisted MAL-PDT once a day for 15 days before illumination on the other side. After 3 months, patients were evaluated for clearance of AKs, side-effects and histopathology before and after the procedure. Protoporphyrin IX (PpIX) fluorescence was measured before and after illumination on both sides.

RESULTS: All 20 patients completed the study. Overall AK clearance rates were 92·1% and 82·0% for CAL-PDT and conventional PDT, respectively (P < 0·001). Grade 1 AKs showed similar response rates for both sides (P = 0·055). However, grade II AKs showed more improvement on the CAL-PDT side (90%) than on the MAL-PDT side (63%) (P < 0·001). Before illumination, PpIX fluorescence intensity was higher on the CAL-assisted side (P = 0·048). The treatment was more painful on the CAL-PDT side, although well tolerated. The mean visual analogue scale score was 5·4 ± 1·4 on the CAL-PDT side and 4·0 ± 0·69 on the conventional MAL-PDT side (P = 0·001). Side-effects such as erythema (P = 0·019), oedema (P = 0·002) and crusts (P < 0·001) were more pronounced on the CAL-assisted side. Histopathological analyses were obtained from five patients and both sides showed improved keratinocyte atypia following PDT, with slightly more improvement on the CAL-assisted side.

CONCLUSIONS: CAL-assisted PDT proved to be safe and more effective than conventional MAL-PDT for the treatment of AKs on the scalp. CAL pretreatment increased PpIX accumulation within the skin and may have enhanced the efficacy in this first human trial.