Abstract
BACKGROUND: Dermatologic toxicities are common among metastatic colorectal cancer (mCRC) patients receiving epidermal growth factor receptor inhibitors (EGFRIs), adversely affecting their well-being and quality of life (QoL). Currently, no validated tool exists in China to measure these symptoms. This study validated the Simplified Chinese version of the Functional Assessment of Cancer Therapy-EGFRI 18 (FACT-EGFRI-18-sC) for QoL assessment in mCRC patients. METHODS: A cross-sectional study was performed via convenience sampling to recruit mCRC patients from two tertiary hospitals in Shenyang, China. Sample size adequacy was confirmed by post hoc power analysis (G*Power 3.1; >80% power for r ≥ 0.3, α = 0.05). Acceptability was assessed by item-level missing data. Reliability was evaluated by Cronbach's α and a 2-week test-retest intraclass correlation coefficient (ICC). Criterion validity was evaluated against the Simplified Chinese version of the patient-reported version of CTCAE (PRO-CTCAE-sC) through non-parametric analyses. Construct validity was assessed via correlations with the Simplified Chinese Body Image Scale (BIS-sC), Karnofsky Performance Status (KPS), and cetuximab cycles using Spearman tests. Diagnostic accuracy and cutoff value were determined via receiver operating characteristic (ROC) analysis. RESULTS: The final sample (n = 184) provided sufficient statistical power, with post hoc analysis revealing 98% power (α = 0.05) to detect correlations exceeding 0.3. The FACT-EGFRI-18-sC showed excellent acceptability (no missing data) and satisfactory reliability (Cronbach's α = 0.899, ICC = 0.875). Moderate to strong negative correlations with PRO-CTCAE-sC (r = -0.436 to -0.803, p < 0.001) and significant FACT-EGFRI-18-sC score differences by dermatologic toxicity status (Z = -4.823 to -7.457, p < 0.001) supported criterion validity. Scores of the FACT-EGFRI-18-sC correlated negatively with BIS-sC (r = -0.565 to -0.619, p < 0.001), positively with KPS physical/functional subscales (r = 0.424/0.541, p < 0.001), but not with the social/emotional subscale (r = 0.125, p > 0.05), confirming construct validity. ROC analysis yielded an area under the curve (AUC) of 0.844 and identified an optimal cutoff of 60.00. CONCLUSIONS: The validated FACT-EGFRI-18-sC is a robust tool for QoL assessment in mCRC patients experiencing EGFRI-related dermatologic toxicities, providing a standardized measure to guide toxicity management.