Efficacy and safety of 0.5% colchicine cream versus 5% 5-fluorouracil cream in the treatment of cutaneous field cancerization: a randomized clinical trial

Background: 5-Fluorouracil (5-FU) is a first-line drug to treat cutaneous field cancerization (CFC). There are few clinical trials with topical colchicine (COL). Objective: To evaluate the effectiveness of 0.5% COL cream versus 5% 5-FU cream in the treatment of CFC. Method: This was a randomized, open, self-controlled clinical trial. Forty-five patients (90 forearms), with three to ten actinic keratoses (AK) on each forearm, used 0.5% COL cream 2×/day for seven days on one forearm, and 5% 5-FU cream 2× /day, for 21 days, on the other forearm. The dosages were defined based on previous clinical trials for each drug. Adverse effects were evaluated after 14 days and outcomes after 90 days of inclusion. The primary outcome was complete AK clearance and the secondary outcomes were: partial clearance (≥50%), reduction in AK count, assessment of the Forearm Photoaging Scale (FPS), AK Severity Score (AKSS), and adverse effects. Results: After 90 days, there was complete clearance of AK in 37% (95% CI 24%–49%) and partial clearance in 85% (95% CI 76%–93%) of the forearms treated with 5-FU,versus 17% (95% CI 7%–27%) and 78% (95% CI 66%–88%) for COL (p > 0.07). There was a percentage reduction of 75% in the AK count of the forearms treated with 5-FU (95% CI 66%–83%) and 64% in those treated with COL (95% CI 55%–72%). Regarding FPS and AKSS, there was improvement in both groups, with no difference regarding FPS (p = 0.654), and 5-FU superiority for AKSS (p = 0.012). Study limitations: Single-center study. Conclusions: 5-FU and COL are effective for treating CFC, with neither showing superiority regarding the reduction in AK counts.