Three-year treatment with imatinib improves survival for high-risk GIST

Issue: July 10, 2011

2011 ASCO Annual Meeting

CHICAGO — A 3-year course of imatinib therapy in patients with gastrointestinal stromal tumors improved OS and RFS compared with the current standard of care, according to study results presented here Sunday.

“What made me very happy was…the overall survival. We are looking at 92% overall survival, which is very high. I think we are making substantial improvement,” said Heikki Joensuu, MD, professor of oncology, Helsinki University Central Hospital, Helsinki, Finland, who presented the results.

Four hundred patients at high risk for recurrence for GIST were enrolled in this prospective, open label, multicenter phase 3 study. Patients received 400 mg oral imatinib (Gleevec, Novartis) daily, and were randomly assigned to either a 1-year or 3-year course of treatment after surgery. The primary endpoint was RFS; secondary endpoints were OS and treatment safety. Median follow-up was 54 months.

The final analysis included 397 patients. Patients in the 3-year group (n=198) had longer RFS compared with patients in the 1 year group (n=197) (HR=0.46; 95% CI, 0.32-0.65). In the 3-year arm, 65.6% of patients had RFS at 5 years, compared with 47.9% in the 1-year arm, a statistically significant difference (P=<.0001).

Patients in the 3-year group also experienced improved OS compared with those in the 1-year group (HR=0.45; 0.22-0.89; 95% CI, 0.22-0.89). Five-year OS in the 3-year group was 92%, compared with 81.7% in the 1-year group.

“There were 55% fewer deaths in the 3-year group, as compared to the 1-year group, a substantial reduction that was also statistically significant,” Joensuu said.

Treatment was generally well-tolerated; side effects included anemia, nausea, fatigue, muscle cramps and diarrhea. In the 3-year group, 13.7% discontinued treatment because of adverse events, whereas 7.7% of patients in the 1-year group discontinued treatment.

Four patients in the 1-year group and 12 patients in the 3-year group halted treatment because of GIST recurrence.

Joensuu addressed concerns about resistance after prolonged treatment. “We need to follow the patients carefully because some of them will get recurrence. There’s evidence that when we restart imatinib, the patients will respond to imatinib again,” he said. “In patients with small tumor volume, there’s a good chance of responding to imatinib for many years.”– by Carey Cowles

Disclosure: Dr. Joensuu has served in a consultant or advisory role for and received honoraria from Novartis.

For more information:

Joensuu H. #LBA1. Presented at: 2011 ASCO Annual Meeting; Chicago; June 3-7, 2011.

I think the entire oncology community was excited when we saw that survival curve at 5 years. Patients who had a 50% death likelihood at 5 years by taking 4 pills a day are alive at 5 years and the vast majority are alive cancer-free. This is the kind of data that changes guidelines.”

– Mark G. Kris, MD, Moderator
Memorial Sloan-Kettering Cancer Center, New York, NY

Disclosure: Dr. Kris has served in a consultant or advisory role with GlaxoSmithKline, Merck, and sanofi-aventis.

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