Longer-term imatinib treatment extends OS among patients with GIST
An extended course of imatinib increased OS among patients with gastrointestinal stromal tumors, or GIST, according to long-term study results presented during the ASCO20 Virtual Scientific Program.
The finding suggests continuing imatinib treatment for 3 years — rather than stopping after 1 year — could reduce by half the number of patients who die during the first decade of follow-up after surgery.
“The current National Comprehensive Cancer Network guidelines recommend postoperative imatinib for at least 3 years after surgical removal of GIST with features that suggest a high risk for recurrence,” Heikki Joensuu, MD, PhD, professor of oncology at University of Helsinki, told Healio. “These recommendations were influenced by the Scandinavian Sarcoma Group XVIII/German (SSGXVIII/AIO) trial that compared 3 years of adjuvant imatinib with 1 year of adjuvant imatinib. In the prior analyses of the SSGXVIII/AIO trial, OS was longer in the 3-year group vs. the 1-year group after median patient follow-up durations of 54 months and 90 months.”
In the current analysis of the SSGXVIII/AIO trial, Joensuu and colleagues assessed whether the survival advantage of the 3-year group persisted after 10 years of follow-up.
The open-label, randomized, multicenter phase 3 trial included 400 patients with macroscopically completely excised GIST and high risk for recurrence. After surgery, researchers assigned patients to 400 mg daily imatinib for 1 year or 3 years.
RFS served as the primary endpoint. Secondary endpoints included OS and safety.
Median follow-up was 119 months. During this time, 18 patients in the 1-year group and 23 patients in the 3-year group were excluded from the study.
Investigators observed 194 RFS events and 96 OS events in the intention-to-treat population.
Researchers reported higher RFS rates in the 3-year imatinib group at 5 years (71% vs. 53%) and 10 years (53% vs. 42%; HR = 0.66; 95% CI, 0.49-0.87).
Results also showed higher OS rates in the 3-year imatinib group at 5 years (92% vs. 79%) and 10 years (86% vs. 65%; HR = 0.55; 95% CI, 0.37-0.83).
Results of a subgroup analysis that excluded 15 patients who did not have GIST per central pathology review and 24 patients with intra-abdominal metastases removed at surgery showed 10-year OS of 81.6% in the 3-year group and 66.8% in the 1-year group (HR = 0.5; 95% CI, 0.32-0.8).
“We found that 3 years of adjuvant imatinib improved OS compared with 1 year of imatinib after a median 10 years of follow-up since the date of randomization,” Joensuu told Healio. “Approximately 50% of deaths from any cause were avoided with the longer treatment, which suggests that 3 years of adjuvant imatinib should be considered for [patients with GIST] who have a high estimated risk for GIST recurrence and whose tumor harbors an imatinib-sensitive KIT or PDGFRA gene mutation.
“Adjuvant imatinib treatment durations of longer than 3 years have not been evaluated in the treatment of GIST in randomized trials,” Joensuu added. “However, there are two ongoing randomized trials comparing 5 or 6 years of adjuvant imatinib with 3 years of imatinib.” – by Jennifer Southall
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Joensuu H., et al. Abstract 11503. Presented at: ASCO20 Virtual Scientific Program; May 29-31, 2020.
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