Clinical activity of sorafenib in patients with advanced gastrointestinal stromal tumor bearing PDGFRA exon 18 mutation: a case series

PDGFRA is mutated in 5%–10% of gastrointestinal stromal tumors (GISTs), the PDGFRA D842V mutation accounting for ∼60% of all PDGFRA mutations known in GISTs [1]. The DIMH842–845 and the IMH843–846 deletions represent ∼15% of all PDGFRA mutations. While the latter have been associated with sensitivity to imatinib, the PDGFRA D842V mutation confers primary resistance to imatinib [1–4], sunitinib [5], and nilotinib [6]. In vitro data suggested that dasatinib is a potent inhibitor of PDGFRA D842V [7]. Sorafenib also displayed some intermediate efficacy even if it was significantly lower than for PDGFRA ΔDIM842–844 [7]. Given the rarity of metastatic GIST with PDGFRA mutation, clinical data in this setting are almost nonexistent [8]. We report here a series of five patients with metastatic GIST bearing a mutation of the exon 18 of PDGFRA and treated with sorafenib (400 mg twice daily).