Nine years ago, researchers with SWOG (formerly the Southwest Oncology Group) confirmed a new standard of care for patients with incurable gastrointestinal stromal tumors (GISTs), who could survive by being treated with imatinib mesylate (Gleevec, Novartis). Now SWOG investigators are back with long-term findings from that study, which estimate that nearly one in four patients treated with Gleevec will survive for 10 years. The findings were published in JAMA Oncology.
SWOG is an international cancer research community supported by the National Cancer Institute (NCI).
In the new study, SWOG researchers report a follow-up of patients originally enrolled in the S0033 trial, a SWOG-led study supported by other groups in the NCI’s National Clinical Trials Network (NCTN). S0033 was a phase 3 trial that began in 2000. Initial results, published in 2008, confirmed that imatinib was an effective treatment for patients with advanced GIST, and recommended that therapy start with a 400-mg daily dose. The SWOG team collected post-study data on these patients from 2011 to 2015. As part of their research, the team used next-generation DNA sequencing on some tumor tissue samples taken for the S0033 study; these samples had been deposited in a biospecimen bank. The team reanalyzed tissue from 20 patients originally classified as having a wild-type tumor––i.e., one without any mutations of KIT, a gene implicated in 85% to 88% of GISTs.
An analysis showed that of the 695 eligible patients originally enrolled in the S0033 study, 189 survived eight years or longer, with a 10-year estimate of overall survival of 23%, or nearly one in four patients. DNA sequencing also showed that survival rates were significantly higher for patients with KIT exon-11–mutant GIST compared with patients whose tumors had a KIT exon-9 mutation or who had no KIT mutations or mutations in the platelet-derived growth factor receptor gene (PDGFR).
GISTs are different from more-common types of gastrointestinal tumors because of the type of tissue in which they start. GISTs belong to a group of cancers called soft-tissue sarcomas. Soft-tissue sarcomas develop in the tissues that support and connect the body, including muscles, nerves, tendons, and joints. GIST is a rare cancer, with approximately 6,000 new cases diagnosed in the United States each year.
Source: EurekAlert; February 20, 2017.