Complete remission of a metastatic gastrointestinal stromal tumour with the tyrosine kinase inhibitor imatinib (STI 571): effect of low dosage in an advanced tumour with exon 11 mutation.

We report a 51-year-old man with an advanced malignant metastatic gastrointestinal stromal tumour, who showed a complete response after 5 months of treatment with imatinib at a dose of 400 mg per day. An early treatment response was demonstrated in an 18fluorodeoxyglucose positron emission tomography scan after 1 month of therapy. Complete remission was documented histologically by negative serial biopsies of residual tumour nodes after 5 months of therapy. No serious side effects were seen with imatinib. A 21 bp, exon 11, in-frame mutation of the c-kit gene was found by DNA sequence analysis of tumour tissue.