Rectal GIST-Outcomes and viewpoint from a tertiary cancer center.

INTRODUCTION: There is scarce data relating to methods to improve sphincter preservation in rectal gastrointestinal stromal tumor (GIST). Increasing the duration of neoadjuvant (NA) imatinib resulting in improved sphincter preservation rate has not been established. This retrospective analysis looks at the rates of sphincter preservation in rectal GIST with NA imatinib and effect of duration of NA imatinib on the same to find out optimum duration of NA with respect to sphincter preservation in rectal GIST patients.

METHODS: Twenty-three cases of GIST of lower third of rectum were treated at our centre from 2005 till 2015. NA imatinib was used in a dose of 400 mg. Response evaluation was done every 3 months with a pelvic magnetic resonance imaging. Surgical management was determined by a team of experienced gastrointestinal oncosurgeons.

RESULTS: Five patients underwent upfront surgery which included local resection in four patients and abdominoperineal resection in one patient. NA imatinib was used in 69.5 % (16/23) patients. Median duration of NA imatinib was 15 months (3-84 months). Amongst who underwent a sphincter-salvage surgery median duration of NA imatinib was 13 months whereas 18 months in patients who required a sphincter-sacrificing surgery (p = 0.683). The radiologic response included partial response in 75 % (12/16) patients, stable disease in 18.7 % (3/16) and one with progressive disease. Definitive surgical resection was possible in 13 patients (81.3 %) after NA imatinib. Median progression-free survival (PFS) was 120 months in the whole cohort whereas median overall survival (OS) was not reached. Four-year estimated PFS and OS was 81 % and 100 %, respectively. Median disease-free survival in upfront surgery group vs. neoadjuvant imatinib group was 70 vs. 120 months, respectively (p = 0.039).

CONCLUSION: Neoadjuvant imatinib appears to be a useful option in improving chances of sphincter preservation without adversely affecting the outcome. Use of neoadjuvant imatinib leads to improvement in progression-free survival in patients with GIST of lower third of the rectum.