Life-threatening toxicity in a patient with UGT1A1*6 heterozygous polymorphism after irinotecan-based chemotherapy: a case report

Polymorphism of the UGT1A1 gene is known to play an important role in irinotecan pharmacokinetics and severe toxicity. A 71-year-old man with lung cancer (squamous cell carcinoma cT2aN3M0 stage IIIB) received irinotecan and cisplatin with concurrent thoracic radiotherapy. Although all treatments were discontinued after day 7, severe leukopenia, neutropenia, febrile neutropenia, thrombocytopenia, and diarrhea developed. His life was at risk, and his ECOG performance status (PS) fell to 4. He had UGT1A1*6 heterozygous and UGT1A1*28 wild-type gene polymorphisms. Considering its frequency in Asians, we should take care when using irinotecan to treat patients with UGT1A1*6 heterozygous polymorphism