What happened, in summary

A 74-year-old woman who had never smoked was found to have a small right lower-lung nodule in December 2020. Surgery removed the affected lung segment and nearby lymph nodes. Pathology showed Stage I small cell lung cancer, and molecular testing identified a rare EML4-ALK fusion along with TP53 and RB1 mutations. No preventive treatment was given after surgery.

For the first year, follow-up imaging showed no abnormality. Eighteen months after surgery, a right hilar lymph node became enlarged. The lymph nodes remained stable for about a year while the patient declined treatment, but by September 2023 they had enlarged further. A biopsy confirmed recurrent small cell lung cancer and again supported the ALK-fusion finding.

Because she did not want chemotherapy, she started the ALK-targeted drug ensartinib. Within 2 weeks, the lymph nodes began to shrink. A severe drug rash required a dose reduction, but she was able to continue treatment. Further imaging showed continued shrinkage, and by the case cutoff in January 2025 she remained on ensartinib with more than 12 months without progression. Her course illustrates an unusually durable response to ALK-targeted treatment in ALK-fusion small cell lung cancer.