Impressive long-term disease stabilization by nilotinib in two pretreated patients with KIT/PDGFRA wild type metastatic gastrointestinal stromal tumors.

KIT/PDGFRA wild-type (WT) gastrointestinal stromal tumours (GISTs) showed a response rate to imatinib ranging from 0 to 25%. Nilotinib is a new-generation tyrosine kinase inhibitor that has demonstrated clinical activity in pretreated GIST patients. At present, no correlation between nilotinib activity and clinical/pathological/molecular features is available. We report on two WT GIST patients resistant to imatinib and sunitinib, and enrolled in the CAMN107A2201 study who achieved an impressive disease control by nilotinib. Both patients have germ-line mutations in the SDHA gene. In April 2004, a 39-year-old woman presented gastric GIST with multiple liver metastases and was treated with imatinib 400 mg/day, followed by imatinib 800 mg/day and then sunitinib. In August 2007, because of disease progression, she was enrolled in the CAMN107A2201 study and assigned to the nilotinib 800 mg/day arm. In March 2005, a 27-year-old woman started imatinib 600 mg/day and then sunitinib for gastric GIST with multiple liver and lung metastases. In October 2007, because of disease progression, she was enrolled in the CAMN107A2201 study and assigned to the nilotinib 800 mg/day arm. One patient still showed stable disease after 46 months of treatment according to the Response Evaluation Criteria In Solid Tumors, and a partial response after 9 months according to Choi's criteria. The other patient still showed stable disease after 42 months according to Response Evaluation Criteria In Solid Tumors. At present, they continue to receive nilotinib. We report very long-term disease stabilization under nilotinib treatment in two pretreated WT GIST patients. In-vitro studies and clinical analyses are warranted to evaluate a potential correlation between nilotinib activity and WT genotype or other clinical/pathological features.