Neoadjuvant imatinib: longer the better, need to modify risk stratification for adjuvant imatinib

Multimodality treatment of gastrointestinal stromal tumor (GIST) with surgery and adjuvant imatinib mesylate (IM), along with an emerging role for neoadjuvant IM prior to evaluation for resectability has resulted in high survival rates.

We conducted a retrospective analysis of prospectively collected data of patients who underwent surgery for GIST, prior to or followed by IM therapy. A total of 112 patients underwent surgery between January 2009 and March 2015 at our centre. This included 27 patients with upfront resectable disease, 76 patients with locally advanced GIST who received neoadjuvant IM followed by surgery and 9 patients with metastatic disease who had excellent response to IM and were taken for surgery.

The primary tumor in the non metastatic patients was in the stomach (53%), duodenum (16%), rectum (12%), jejunum (11%), ileum (7%), and others (2%). Median duration of neoadjuvant IM was 5 months with 4 patients showing disease progression during neoadjuvant IM. Ninety-three percent of all patients had R0 resections, while 7% had R+ resections. The estimated 3- and 5-year DFS in non-metastatic patients was 86.1% and 67% respectively with a 3- and 5-year median OS of 95.4% and 91.7% respectively. Five-year PFS and OS for the metastatic patients was 88.8% and 100% respectively. Lack of adjuvant IM was the only factor related to inferior PFS and OS.

Longer duration of neoadjuvant IM should be considered in locally advanced GIST prior to surgery and resection may be considered in responding metastatic patients.