Effectiveness and safety of 0·5% colchicine cream vs. photodynamic therapy with methyl aminolaevulinate in the treatment of actinic keratosis and skin field cancerization of the forearms: a randomized controlled trial

Summary Background Skin field cancerization ( SFC ) is a process that occurs in areas of the skin that have undergone genomic alterations induced by ultraviolet radiation. Actinic keratosis ( AK ) is a sign of its activity. Objectives To evaluate the effectiveness and safety of 0·5% colchicine ( COL ) cream vs. methyl aminolaevulinate photodynamic therapy ( MAL ‐ PDT ) in the treatment of AK and SFC . Methods We conducted a randomized, open, intrasubject controlled trial. A total of 36 participants with 3–10 AK s on each forearm were treated with either COL cream (twice daily for 10 days) or a single session of MAL ‐ PDT and were reassessed after 60 days. The clinical evaluation was performed using AK count, forearm photoageing scale ( PAS ) and AK degree ( AKD ). Patients underwent central forearm biopsies and histopathological evaluation by keratinocyte intraepithelial neoplasia ( KIN ) assessment, epithelial atrophy and immunohistochemistry (p53/Ki67). Results Overall, 50% of patients were male. The mean age was 70·9 years ( SD 8·6) and phototypes I and II were predominant (89%). Total clearance was observed in six (17%) forearms treated with COL and seven (19%) forearms treated with MAL ‐ PDT ( P = 0·76); partial clearance was observed in 44% of forearms in the COL group and 67% of forearms in the MAL ‐ PDT group ( P = 0·07). In both COL and MAL ‐ PDT groups, reductions in PAS (−6% vs. −6%) and AKD (−45% vs. −40%) were observed. KIN normalized in 28% of patients treated with MAL ‐ PDT and 20% of those treated with COL . Epithelial atrophy reduced after treatment ( P < 0·01). Expression levels of Ki67 and p53 were also assessed. Mild or moderate adverse effects were similar for both groups. Conclusions COL 0·5% cream and MAL ‐ PDT are safe and effective for treating SFC .