Weight loss in patients on osimertinib for metastatic EGFR-mutant non-small cell lung cancer.

Background: Cachexia is characterized by weight loss and decline in muscle mass and function and is a poor prognostic factor among patients with cancer. Patients with metastatic EGFR-mutant non-small cell lung cancer (NSCLC) derive remarkable survival benefits with osimertinib, a third-generation EGFR tyrosine kinase inhibitor. It is not known whether patients treated with osimertinib experience any weight loss or whether weight loss impacts patient outcomes. Therefore, we sought to describe the frequency and consequences of weight loss in this patient population.

Materials and methods: We conducted a single-center retrospective pilot study of 56 patients treated with first-line osimertinib for metastatic EGFR-mutant NSCLC. We defined on-treatment weight loss as a loss of ≥5% body weight at 6 or 12 months of treatment. We described the characteristics of patients with and without on-treatment weight loss and differences in progression-free survival (PFS), time on treatment with osimertinib, and overall survival (OS).

Results: Forty-six percent (n = 26) of patients met the criteria for on-treatment weight loss. There were no significant differences in patient or disease characteristics between patients with and without weight loss. Compared to patients without weight loss, patients with weight loss had similar PFS and time on treatment with osimertinib. Yet, patients with weight loss had significantly worse overall survival (HR 4.91, 95% CI, 1.56-15.5, P = .007).

Conclusion: Weight loss was observed in nearly half of patients with metastatic EGFR-mutant NSCLC treated with osimertinib, and patients with weight loss had significantly worse overall survival.