Progression of advanced gastrointestinal stromal tumour after over 20-year response to imatinib.

Imatinib is the standard first-line treatment for advanced gastrointestinal stromal tumours (GISTs). Most patients either respond to imatinib or achieve disease stabilisation for several years, but only approximately 10% remain free from GIST progression 10 years after starting therapy. The maximum duration of response to imatinib remains uncertain. We report the case of a woman with multiple liver metastases from a gastric GIST at the time imatinib was initiated. The metastases responded to the standard dose of imatinib, which was continued and the patient was monitored with periodic abdominal imaging. GIST recurrence was detected in the distal oesophagus 20.8 years after starting imatinib. In addition to a KIT exon 11 deletion mutation, the recurrent tumour harboured an imatinib resistance mutation in exon 13 (p.Val654Ala). This case demonstrates that GIST may progress as late as 20 years after initiation of imatinib. Periodic abdominal imaging is essential even for long-term responders.