Primary Management of Localized Gastrointestinal Stromal Tumors With Imatinib Monotherapy: An Alternative to Resection of Patients Precluded From Surgery.

Background: In this study, our goal was to elucidate the role for imatinib monotherapy for treatment of patients with localized gastrointestinal stromal tumors (GISTs) who are precluded from standard-of-care surgical resection due to their medical comorbidities or patient preference.

Methods: A single-center retrospective study was conducted on a consecutive cohort of adult patients with pathology-confirmed gastrointestinal stromal tumors. The cohort of interest (n = 11) was the subset of patients on imatinib therapy alone with no prior history of curative-intent surgical resection. We analyzed patient demographics, GIST disease characteristics, treatment type, and medical comorbidities at the time of diagnosis. Overall survival (OS) and progression-free survival (PFS) were assessed using Kaplan-Meier univariate analysis.

Results: Eleven patients met our inclusion criteria. Median age was 77 years (range 65-82) and 7 patients (64%) were men. Eight cases were gastric primary, 2 cases were duodenal, and 1 was esophageal. Four cases had genomics available, 3 of which harbored KIT mutations. For all cases, the documented mitotic rate was less than 5 per 5 mm². Median tumor size was 38 mm (range 20-58 mm). The most common medical comorbidity precluding patients from surgery was cardiac disease. All patients received imatinib as their only treatment modality and median time on treatment was 16 months. Two patients had progression of disease through treatment. Treatment was generally well tolerated with no documented grade III or grade IV adverse events. With a median follow-up of 35 months, the 1-year PFS and OS were 90% and 100%. The 3-year PFS and OS were also 90% and 100%.

Conclusion: Patients tolerated imatinib monotherapy well and demonstrated robust survival data. Our research highlights a new potential application for imatinib in a patient population that has historically been precluded from standard-of-care therapy for their disease.