Adjuvant Treatment of Gastrointestinal Stromal Tumor: The Proof, The Pro, and the Practice

Abstract

Overview:Gastrointestinal stromal tumors (GIST) are rare tumors, but they are the most common mesenchymal tumor of the gastrointestinal tract, driven by mutations in KIT and PDGF. The KIT and PDGF inhibiting agent imatinib has been tested as adjuvant postsurgery in GIST patients with an intermediate or high risk of relapse. Two of three prospective, randomized controlled studies have meanwhile been reported. The American College of Surgical Oncology Group (ACOSOG) in 713 patients reported a relapse-free survival benefit for adjuvant imatinib given for 1 year, but not an overall survival benefit. The Scandinavian Sarcoma Group (SSG) performed a study comparing 1 year of imatinib to 3 years of imatinib. At 3 years the overall survival (OS) in patients with 3 years of imatinib therapy was similar to the OS in those with 1 year of imatinib 96% and 94% respectively, while at 5 years these numbers were 92% and 82% (HR: 0.45; 95% CI [0.22–0.89]; p = 0.019). Data from the largest study, conducted by the European Organisation for Research and Treatment of Cancer (EORTC) in 908 patients randomly assigned to receive either 2 years of adjuvant imatinib or no imatinib, have not yet been reported. Based on the current evidence, 3 years of imatinib at a daily dose of 400 mg should be considered in patients with a 50% or higher risk of relapse within 5 years after surgery. The evidence and the remaining caveats are discussed.