Imatinib mesylate for the treatment of gastrointestinal stromal tumor

Gastrointestinal stromal tumors (GISTs) are rare neoplasms of mesenchymal origin arising in the GI tract. These tumors are characterized by activating mutations of either receptor tyrosine kinase KIT or PDGFRA, which are found in 85% of cases. The introduction of imatinib mesylate (IM), which targets the kinases presenting with these molecular alterations, has dramatically changed the management of these rare tumors, which were resistant to conventional cytotoxic chemotherapy, both in advanced and localized phases. IM is orally available, has a favorable safety profile and induces partial responses and disease stabilization in up to 80% of patients with advanced GIST. Recently, IM was approved for the postoperative treatment of patients with completely resected localized GIST.

A prospective epidemiological study of new incident GISTs during two consecutive years in Rhône Alpes region: incidence and molecular distribution of GIST in a European region

Background:

Preliminary data indicate that the molecular epidemiology of localised gastrointestinal stromal tumour (GIST) may be different from that of advanced GIST. We sought to investigate the molecular epidemiology of sarcomas, including GIST, in the Rhone-Alpes region in France.

Patients and methods:

A prospective and exhaustive study in the Rhone-Alpes Region in France to assess the precise incidence of primary sarcomas with systematic centralised pathological review and molecular analysis was conducted for 2 consecutive years.

Results:

Among 760 patients with a confirmed diagnosis of sarcoma, 131 (17%) had a GIST. The majority of patients had gastric primaries (61%). Mutational analysis could be performed in 106 tumour samples (74%), and 71 (67%) had exon 11 mutations. PDGFRA mutations were found in 16% of cases, which is twice as high as previously reported for advanced GIST.

Conclusion:

Data indicate that PDGFRA mutations in localised GIST may be twice as high as what was previously reported in patients with advanced disease. This finding may have important consequences for patients offered adjuvant imatinib, although most of these tumours are in the low-risk group.

Novel approaches to gastrointestinal stromal tumors resistant to imatinib and sunitinib

Gastrointestinal stromal tumors (GIST) are rare tumors of mesenchymal origin that may arise anywhere along the gastrointestinal tract or in the peritoneum. In most cases, GIST harbor mutations of KIT or PDGFRA. Imatinib mesylate (IM), a small-molecule tyrosine kinase inhibitor developed for the treatment of chronic myeloid leukemia, has been shown to be active against these mutations and has significant activity in patients with metastatic GIST. However, resistance to IM emerges after a median of 24 months of treatment. Sunitinib malate (SU) has been approved for the treatment of patients with IM-resistant advanced GIST, but the median progression-free survival in this setting is only 6 months. This article reviews the current knowledge regarding IM and SU resistance in GIST, as well as the available options for the management of GIST resistant to IM and SU.