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

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.

Figures

Fig. 1

Schematic representation of RTOG 0132 trial – Phase II Trial of Neoadjuvant/Adjuvant Imatinib Mesylate for Advanced Primary and Metastatic/Recurrent Operable Gastrointestinal Stromal Tumor

Fig. 2

Progression Free Survival with a median F/U of 3 years.

Fig. 3

Overall survival with a median F/U of 3 years