Second Clinical Scenario - Intolerance Versus Resistance Management

Dr. Shameem presents the second clinical scenario involving a 72-year-old woman with mutated IGHV and del(17p) detected at relapse. Her first-line therapy was covalent BTKi for 18 months achieving partial response, but treatment was discontinued due to recurrent atrial fibrillation and uncontrolled hypertension representing cardiac toxicity issues. Six months later, she developed progressive lymphocytosis, splenomegaly, and fatigue.

Laboratory testing revealed white blood cell count 58,000, hemoglobin 10.8 g/dL, platelets 122,000, with normal renal function. BTK resistance mutation testing showed no mutations detected, distinguishing this case as intolerance rather than resistance. Patient considerations include cardiac toxicity concerns with new therapy given prior covalent BTKi issues.

Dr. Xavier emphasizes having substantial clinical experience with similar intolerance cases. Switch trials demonstrate data for transitioning between covalent BTKis, particularly first-generation versus next-generation agents, to assess whether toxicities return at similar grades or remain manageable with different covalent BTKi selection. Non-covalent BTKis potentially offer favorable toxicity profiles, though head-to-head comparisons are limited except for emerging frontline studies comparing ibrutinib versus pirtobrutinib.

For dose-limiting toxicity scenarios from previous covalent BTKis, having additional treatment options benefits patients who prefer avoiding BCL-2-based therapy. Re-challenging with different continuous BTKis provides valuable alternatives, particularly when transitioning from ibrutinib with highest cardiotoxicity rates to alternative covalent BTKis or non-covalent options.

Importantly, intolerant patients retain the full spectrum of treatment options since they have not progressed or developed resistance to covalent BTKis. Treatment alternatives include different covalent BTKis, non-covalent BTKis, or BCL-2-based treatments with tumor lysis syndrome risk assessment, though this patient demonstrates progressive lymphocytosis with only mild splenomegaly, which represents relatively lower tumor lysis syndrome risk compared to bulky adenopathy scenarios.