Phase II trial of neoadjuvant/adjuvant imatinib mesylate (IM) for advanced primary and metastatic/recurrent operable gastrointestinal stromal tumor (GIST): Early results of RTOG 0132/ACRIN 6665

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Abstract
Background: Therapy for gastrointestinal stromal tumors (GIST) has changed significantly with the use of imatinib mesylate (IM). Despite the success of this drug in metastatic GIST, disease progression remains a perplexing clinical issue suggesting the need for multimodality management. There have been no prospective studies either evaluating the neoadjuvant use of IM in primary GIST or as a preoperative cytoreduction agent for metastatic GIST.Methods: RTOG 0132/ACRIN 6665 was a prospective phase II study evaluating safety and efficacy of neoadjuvant IM (600 mg/day) for patients with primary GIST or the preop use of IM in patients with operable metastatic GIST. The trial continued postop IM for 2 years.Results: Sixty‐three patients were entered (52 analyzable), 30 patients with primary GIST (Group A) and 22 with recurrent metastatic GIST (Group B). Response (RECIST) in Group A was (7% partial, 83% stable, 10% unknown), in Group B (4.5% partial, 91% stable, 4.5% progression). Two‐year progression free survival (Group A 83%, Group B 77%). Estimated overall survival (Group A 93%, Group B 91%). Complications of surgery and IM toxicity were minimal.Conclusion: This trial represents the first prospective report of preop IM in GIST. This approach is feasible, requires multidisciplinary consultations, and is not associated with notable postop complications. J. Surg. Oncol. 2009;99:42–47.