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Background: Gastrointestinal stromal tumors (GIST) represent an uncommon form of malignancy and one of best paradigms of molecularly targeted therapy. While the natural history of GIST following treatment with imatinib mesylate is relatively well known from various series in western literature, rarely any series from India has been published in this regard. Materials and Methods: Forty-four GISTs cases diagnosed and treated with imatinib between 2005 and 2011 were retrieved from the Department of Medical Oncology database, KMIO, Bangalore. Their clinical, histopathological data, and treatment outcome were analyzed. Kaplan-Meier survival analysis was done. Anatomic site, tumor size, mitotic activity, and extent of resection were correlated with overall survival (OS) using the logrank test. Results: Median age was 56 years with a male: female ratio of 2:1. Stomach was the most common site involved. Twenty-nine patients had localized disease of which majority had high risk (65%) features, with a mean tumor size of 10.5 cm (range 4-18 cm) and mitotic rate of 6 (range 4-9)/50 high-power field (HPF). Fourteen patients had metastatic disease at presentation with liver being the most common site. In the adjuvant group, median follow-up was 42 months (m) (range 10-70 m). Estimated recurrence free survival (RFS) and OS at 42 m were 59.9 and 80.6%, respectively. In metastatic group, median follow-up was 28 m (range 2-54 m). The median progression free survival (PFS) and OS were 18 m (95% CI 8.65-27.34 m) and 28 m (95% CI 17.90-38.09 m), respectively. Estimated PFS and OS at 28 m were 38.7 and 46.7%, respectively. Conclusion: Patients with GIST still present with larger bulky tumor at diagnosis, this leads to slightly inferior survival in our scenario. Nongastric GISTs; R1 and R2 resection; and mitotic rate >5/50 HPF are the other a factors which have a negative impact on survival.
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