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Extended Imatinib Therapy Post-Resection Improves Survival in High-Risk GIST

A secondary analysis from a phase 3 trial showed that 3 years of adjuvant imatinib therapy significantly improved recurrence-free survival (RFS) and overall survival (OS) compared with 1 year of imatinib treatment, after surgery, in patients with high risk-gastrointestinal stromal tumor (GIST; JAMA Oncol. 2020 May 29. Epub ahead of print).

“Adjuvant imatinib is associated with improved recurrence-free survival (RFS) when administered after surgery to patients with operable… [GIST], but its influence on… [OS] has remained uncertain,” wrote Heikki Joensuu, MD, Department of Oncology, Helsinki University Hospital and University of Helsinki, Helsinki, Finland and co-investigators.

In order to evaluate the effect of adjuvant imatinib on survival in patients at high risk for GIST recurrence after surgery, Dr Joensuu and colleagues conducted an open-label, randomized, multicenter phase 3 study.

The trial enrolled 400 patients between February 2004 and September 2008. After surgery, patients received oral imatinib 400 mg daily for either 1 or 3 years. Data for this follow-up analysis were analyzed between September and November 2019.

The primary end point was RFS. Secondary end points included OS and safety.

The intention-to-treat population included 397 patients randomized to either the 1-year imatinib (n = 199) or 3-year imatinib (n = 198) arms. Median follow-up was 119 months, during which 194 RFS events and 96 OS events were reported.

5-year RFS was 71.4% and 10-year RFS was 52.5% in the 3-year imatinib arm compared with 53% and 41.8%, respectively, in the 1-year imatinib arm (hazard ratio [HR], 0.66; 95% CI, 0.49-0.87; P = .003). 5-year OS was 92% and 10-year OS was 79% in the 3-year imatinib arm versus 85.5% and 65.3%, respectively, in the 1-year imatinib arm (HR, 0.55; 95% CI, 0.37-0.83; P = .004).

Results were found to be similar in the efficacy population, with 10-year OS of 81.6% in the 3-year imatinib arm and 66.8% in the 1-year imatinib arm (HR, 0.50; 95% CI, 0.32-0.80; P = .003).

Additionally, Dr Joensuu and colleagues noted that no new safety signals were detected.

“Three years of treatment with adjuvant imatinib was associated with improved OS compared with 1 year of imatinib in patients with high-risk GIST. Approximately 50% of deaths may be avoided during the first 10 years of follow-up after surgery with longer adjuvant imatinib treatment,” they concluded.—Kaitlyn Manasterski

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