Long-term clinical outcomes of imiquimod 5% cream vs. diclofenac 3% gel for actinic keratosis on the face or scalp: a pooled analysis of two randomized controlled trials

Abstract

Background: Actinic keratosis (AK) is an early in situ epidermal cancer which can progress to invasive squamous cell carcinoma (SCC). Imiquimod 5% cream (IMIQ) and diclofenac 3% gel (DIC) are frequently used to treat AK; however, their long-term effects following repeated treatment cycles have never been compared. Objective: To compare IMIQ and DIC in the treatment of AK with respect to the risk of change to grade III AK or invasive SCC, after 3 years. Methods: Data were pooled from two randomized, active-controlled, open-label, multicentre, multinational, phase IV studies (Clinicaltrials.gov NCT00777127/NCT01453179), with two parallel groups. Studies were conducted between 2008 and 2015 and were almost identical in design. Patients eligible for inclusion were immunocompetent adults with 5–10 visible AK lesions on the face/scalp and grade I/II AK. The primary endpoint was inhibition of histological change to grade III AK or invasive SCC in the study treatment area, observed until month 36. Patients applied either IMIQ or DIC for a maximum of six treatment cycles. Results: In total, 479 patients (IMIQ 242; DIC 237) were included in the full analysis set. Histological change to grade III AK or invasive SCC was observed until month 36 in 13 (5.4%) patients treated with IMIQ, compared with 26 (11.0%) patients treated with DIC (absolute risk difference –5.6% [95% confidence interval –10.7%, –0.7%]). Time to histological change was greater in the IMIQ group than the DIC group (P = 0.0266). Frequency of progression to invasive SCC was lower with IMIQ than with DIC at all time points. Initial clearance rate was higher in the IMIQ group compared with the DIC group, while recurrence rate was lower. Both treatments were well tolerated. Conclusions: Over 3 years, IMIQ was superior to DIC in clearing AK lesions and preventing histological change to grade III AK or invasive SCC and recurrence.