What happened, in summary

A 62-year-old Chinese woman was found to have a right lung lesion and enlarged hilar and mediastinal lymph nodes during a physical examination at age 59. She underwent pneumonectomy with mediastinal lymph node dissection. Pathology showed poorly differentiated adenocarcinoma with slight squamous differentiation, bronchial and nerve invasion, and positive lymph nodes at stations 7, 9, and 10. Tumor genetic testing identified an EML4-ALK fusion involving EML4 exon 13 and ALK exon 20. Her initial stage was pT1cN2Mx, but before planned adjuvant therapy, follow-up imaging showed multiple small nodules in the right frontal brain region, revising the diagnosis to Stage IVB disease with brain metastases. She started alectinib and remained on it for nearly 4 years. During that period, the intracranial lesions resolved, no chest recurrence was seen, and the cancer response was evaluated as complete remission. She later developed 4 days of watery diarrhea about 10 times daily. Colonoscopy showed pancolitis with ulcers in the terminal ileum and ileocecal valve. Infection and intestinal tumor were ruled out, and the condition was classified as grade 3 alectinib-associated colitis and ulceration. Alectinib was stopped, and she received oral enteric-coated mesalazine, 1.2 g 3 times daily, plus probiotics. Her diarrhea resolved, the ulcers healed, and after 12 weeks without tumor progression, she switched to ceritinib. Nine months later, the ileocecal valve ulcer had completely healed, and follow-up showed stable tumor control without recurrent intestinal ulcers or colitis. Follow-up imaging showed stable tumor findings after the switch, allowing continued ALK-directed care while avoiding recurrent bowel toxicity and without immediate evidence of cancer progression.