Minimally Important Difference of the FACE-Q Skin Cancer Module: A Distribution-Based and Anchor-Based Analysis

ABSTRACT Background The FACE-Q Skin Cancer Module is a validated patient-reported outcome measure for facial skin cancer surgery. However, the minimally important difference (MID)— the smallest change in score perceived as meaningful by patients—has not been established. Without the MID, individual score changes cannot be interpreted clinically. This study aimed to determine the MID for all four FACE-Q Skin Cancer scales. Methods Prospective cohort study at a tertiary center (2017–2018). Patients completed the FACE-Q preoperatively and at 1 week, 3 months, and 1 year postoperatively. MID was estimated using distribution-based methods (0.5 standard deviation, standard error of measurement) and an anchor-based approach using the FACE-Q Adverse Effects scale as an implicit anchor. Internal consistency (Cronbach’s α), effect sizes, and standardized response means were calculated. Results Of 287 enrolled patients, 111 had paired baseline–three-month data. All scales had strong internal consistency (α = 0.82–0.93). Cancer worry showed the largest improvement from baseline to three months (mean change −3.1 ± 5.8; SRM = −0.54; p < 0.001). When we combined the estimates, the MID values (sum scores / 0–100 scale) were: Appearance Satisfaction 2.0 / 5.6, Psychosocial Distress 2.0 / 6.2, Cancer Worry 2.5 / 6.2, and Scar Satisfaction 2.0 / 6.2. Anchor-based estimates for the Scar scale (2.4 sum points) confirmed distribution-based findings. Conclusions This study establishes the first MID values for the FACE-Q Skin Cancer Module. A change of approximately 2–2.5 sum points (5–6 points on a 0–100 scale) represents a minimally important difference across all scales. These thresholds enable clinicians and researchers to interpret individual FACE-Q score changes and design adequately powered clinical trials.