361P Tucatinib plus trastuzumab in patients (Pts) with HER2-positive metastatic colorectal cancer (mCRC): Patient-reported outcomes (PROs) from ph II study MOUNTAINEER

Abstract

HER2 amplification/overexpression (HER2-positive [HER2+]) is reported in ∼3-5% of all pts with mCRC. Treatment strategies for mCRC focus on prolonging survival, delaying tumor progression, and maintaining health-related quality of life (HRQoL). Tucatinib (TUC) is a highly selective, HER2-directed, tyrosine kinase inhibitor. Results from the MOUNTAINEER (NCT03043313) study demonstrated that dual HER2 inhibition with TUC and trastuzumab (T) in pts with HER2+ RAS WT mCRC is well tolerated with durable clinical benefit. Here we report the impact of TUC + T on HRQoL in pts from MOUNTAINEER. MOUNTAINEER is a global, multi-center, open-label, phase 2 trial that enrolled pts with HER2+ RAS WT mCRC previously treated with fluoropyrimidine, oxaliplatin, irinotecan, and anti-VEGF mAb. Overall, 117 pts were enrolled or randomized to receive TUC + T (cohorts A [n=45] and B [n=41]) or TUC monotherapy (cohort C [n=31]). HRQoL was assessed with EQ-5D-5L and EORTC QLQ-C30 for cohorts B and C. Cohort A was not assessed for HRQoL. Questionnaires were administered at predose on Cycle 1 Day 1 (C1 D1), C1 D8, C1 D15, then every D1 of C2-4 and every 3 following cycles until end of treatment. HRQoL data for cohorts B and C were analyzed using descriptive statistics. Thirty-seven pts in cohort B and 28 pts in cohort C had ≥1 dose of study treatment and completed baseline and at least 1 follow-up HRQoL assessment. For both cohorts, the mean changes from baseline during the treatment period for EORTC QLQ-C30 generally remained stable across all scales, including global health status/QoL and functional domains. Descriptive analyses showed some fluctuations in observed individual domain scores; however, global health status/QoL remained stable over time. EQ-5D-5L VAS scores also remained similar over time. HRQoL was maintained for pts treated with TUC + T or TUC monotherapy throughout the treatment period. These results, together with the primary efficacy and safety data from MOUNTAINEER, further support the overall tolerability profile of TUC + T and suggest this regimen may be an important treatment option for pts with HER2+ mCRC.