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Patients Receiving Adjuvant Imatinib for GISTs Show 97% Survival at 3 Years: Presented at ASCO-GI

By Ed Susman

ORLANDO, FL -- January 26, 2008 -- Patients undergoing surgery for gastrointestinal stromal tumors (GISTs) who receive imatinib mesylate as an adjuvant therapy achieved a 97% survival in a 3-year study, researchers reported.

In this first attempt to use imatinib in an adjuvant therapy, doctors said that of 107 evaluable patients, 61% remained progression-free after 3 years, according to data from the Z9000 trial reported at American Society for Clinical Oncology's 2008 Gastrointestinal Cancers Symposium (ASCO-GI).

The symposium is cosponsored by ASCO with the American Gastroenterological Association Institute, the American Society for Therapeutic Radiology and Oncology, and the Society for Surgical Oncology.

"This shows how well the drug rescues people," said Ronald DeMatteo, MD, Vice Chair, Department of Surgery, and Head, Division of General Surgical Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York.

In his oral and poster presentations on January 25, Dr. DeMatteo said that in the first year after giving imatinib following surgery the recurrence-free survival rate was 94% and by the end of the second year it was 73%. "So, roughly speaking, 1 year of imatinib protects you for about 1 to 1.5 years, and then patients are at much higher risk of recurrence," he said.

A phase 3 trial conducted at the same time (Z9001) that was expected to randomize 805 patients with tumors greater than 10 cm to adjuvant imatinib or placebo was stopped early based on a significant (P <.001) benefit for imatinib in both recurrence-free and overall survival.

Dr. DeMatteo said the results of the Z9000 and Z9001 studies were "basically superimposable."

The Z9000 trial was a single-arm, open-label, multicenter study of adjuvant imatinib at a dose of 400 mg for 1 year initiated within 84 days of surgery. All patients underwent complete gross resection of KIT-expressing primary GISTs that met criteria for high risk of recurrence, defined as tumor size large than 10 cm, tumor rupture, or less than five peritoneal metastases.

Patients were enrolled from September 2001 through September 2003. The median age of patients was 58 years and median tumor size was 13 cm. Half of the tumors originated from the stomach and 42% from the small intestine.

At a median follow-up of 4 years, the overall survival rates were 99% at 1 year, 97% at 2 years, and 97% at 3 years.

Asked about duration of adjuvant therapy, Dr. DeMatteo said, "That's the million dollar question."

If the goal is to prolong recurrence-free survival rather than overall survival, "most likely a year of therapy is indicated and we are trying to design a trial to answer the duration question, which I think is the most important question at this time."

Funding for this study was provided by Novartis.


[Presentation title: Efficacy of Adjuvant Imatinib Mesylate Following Complete Resection of Localized, Primary Gastrointestinal Stromal Tumor (GIST) at High Risk of Recurrence: The U.S. Intergroup Phase II Trial ACOSOG Z9000. Abstract 8]

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