LAUSR

Background: Hypoalbuminemia is commonly observed in cancer patients. Given the pharmacokinetic interactions between serum proteins and protein bound medications, administration of highly protein bound targeted oral oncolytic drugs may result in elevated unbound drug levels and decreased tolerability in those with hypoalbuminemia. Objective: To describe the impact of hypoalbuminemia on oral oncolytic drug tolerability. Methods: A retrospective study was conducted of adult patients receiving treatment with targeted oral oncolytic drugs with ≥95% protein binding. The primary end point of this study was to compare time to discontinuation resulting from documented toxicity in those with and without hypoalbuminemia. Results: The study included 143 patients receiving 16 targeted oral oncolytic drugs (42% with hypoalbuminemia, 58% without hypoalbuminemia). Adverse events were common, with similar incidence among patients with and without hypoalbuminemia (73% vs 76%, respectively; P = 0.727). Median time to therapy discontinuation resulting from documented toxicity was significantly shorter in those with hypoalbuminemia (22 months vs not reached; P = 0.003). Cox regression demonstrated that hypoalbuminemia was the only significant risk factor for shorter time to discontinuation resulting from documented adverse effects (hazard ratio = 3.0; 95% CI = 1.15-8.0; P = 0.025). Conclusion and Relevance: This represents the first report of the impact of hypoalbuminemia on tolerability of highly protein bound oral oncolytic drugs, demonstrating that patients with hypoalbuminemia may be at increased risk for early discontinuation resulting from toxicity. Given the importance of maintaining dose intensity in patients receiving oncolytic therapy, albumin levels should be monitored throughout treatment and supportive care maximized in those developing hypoalbuminemia.