SWOG Study Shows Robust, Longer Survival With Imatinib Therapy for GIST

When treated with imatinib, patients with GIST may live for 10 years or longer.
When treated with imatinib, patients with GIST may live for 10 years or longer.

SWOG researchers showed that approximately one-quarter of patients with incurable gastrointestinal stromal tumors (GISTs) treated with imatinib mesylate (Gleevec) live another 10 years. Based on study results from 9 years ago, SWOG established imatinib as the standard of care for patients with incurable GIST.1

SWOG is a worldwide network of researchers who design and conduct oncologic clinical trials. The National Cancer Institute supports SWOG.

"This is a really exciting finding," said Michael Heinrich, MD, a SWOG investigator and a professor of medicine and cell and developmental biology at Oregon Health & Science University in Portland.

Previously, patients with advanced GIST had a life expectancy of 18 months. With imatinib treatment, some patients may live for 10 years or longer. Furthermore, we have a better understanding of which group of patients will benefit the most from treatment with imatinib, explained Dr Heinrich.

These results are a follow-up of patients who were originally enrolled in S0033, a phase III trial that began in 2000. Its initial results confirming imatinib as an efficacious therapy for patients with advanced GIST were published in 2008.

These results present data collected between 2011 and 2015 after the conclusion of S0033. Of the 695 patients originally enrolled, 189 patients survived 8 years or more. The 10-year estimate of overall survival is 23%.

As part of this study, researchers sequenced the DNA from some tumor samples collected for S0033 and maintained in a biospecimen bank.

Researchers specifically focused on re-analysis of tumors from 20 patients originally classified as having tumors without any mutations in KIT. KIT mutations are associated with 85% to 88% of all GISTs.

Survival rates were higher in patients with a KIT exon-11 mutant GIST compared with patients with a KIT exon-9 mutation, patients with no KIT mutations, or patients with mutations in platelet-derived growth factor receptor (PDGFRA).

"Our findings show two things," Heinrich said. "One is that Gleevec has revolutionized treatment for patients with advanced GIST. Our findings also highlight the importance of banked biospecimens to drive new scientific findings, and how tumor mutation testing can optimize treatment for cancer patients."

Reference

1. Heinrich M, Rankin C, Blanke CD, et al. Correlation of long-term results of imatinib in advanced gastrointestinal stromal tumors with next-generation sequencing results: analysis of phase 3 SWOG Intergroup Trial S0033. JAMA Oncol. 2017 Feb 9. doi: 10.1001/jamaoncol.2016.6728 [Epub ahead of print]

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