Association of progression-free survival, overall survival, and patient-reported outcomes by skin toxicity and KRAS status in patients receiving panitumumab monotherapy

BACKGROUND: The authors explored the association of skin toxicity (ST) severity as measured by patient- reported ST and Common Terminology Criteria for Adverse Events (CTCAE) grading with efficacy of pani- tumumab, a fully human antiepidermal growth factor receptor antibody, from a phase 3 metastatic colorec- tal cancer (CRC) trial. METHODS: Patients were randomized to panitumumab plus best supportive care (BSC) vs BSC alone. ST by modified National Cancer Institute CTCAE v3.0 and modified Dermatology Life Quality Index (mDLQI), health-related quality of life (HRQOL), and CRC symptoms were measured. ST was analyzed using a landmark approach. Associations by KRAS mutational status were also assessed. RESULTS: Of 463 patients, 208 of 231 (90%) panitumumab patients and 184 of 232 (79%) BSC patients had ≥1 postbaseline patient-reported outcome (PRO) assessment. Panitumumab patients with more severe ST had significantly longer overall survival (OS) (grade 2-4:grade 1; hazard ratio, 0.60; P =.0033). Lower mDLQI scores (<67; more bothersome ST) were associated with longer OS (Cox model, P <.0001). Similar results were observed with progression-free survival (PFS). An inverse relation between mDLQI and HRQOL scores was observed, suggesting that ST bother correlated with better HRQOL. KRAS and PRO data were available in 363 patients (188 panitumumab; 175 BSC). Longer OS was associated with lower mDLQI scores, regardless of KRAS status. Longer PFS was associated with more severe ST (lower mDLQI scores and higher CTCAE grade ST) in patients with wild-type (WT) KRAS tumors, but not in patients with mutant KRAS tumors. CONCLUSIONS: More severe ST, by both clinical grading and PRO, is associated with better CRC symptoms and HRQOL and with longer OS and PFS among panitumumab-treated patients. The associations for PFS were more pronounced in patients with WT KRAS tumors.