A review of resistance patterns and phenotypic changes in gastrointestinal stromal tumors following imatinib mesylate therapy.

Gastrointestinal stromal tumors are neoplastic lesions that arise from the interstitial cells of Cajal and are associated with somatic mutations in the tyrosine kinase receptor, KIT. The only known curative therapy is complete surgical resection. Unfortunately, postsurgical recurrence rates exceed 50% and most tumors are resistant to standard chemotherapy and radiation. Imatinib mesylate, a novel tyrosine kinase inhibitor, holds promise as a potential adjuvant therapy to prevent recurrence and improve long-term survival. However, as resistance data emerge, it appears that a potential "escape pathway" may originate from secondary mutations in the KIT receptor. This paper reviews the historical clinical experience with imatinib mesylate and discusses resistance patterns following targeted therapy. We highlight this review with an interesting case report that illustrates unique phenotypic tumoral changes associated with imatinib mesylate resistance.