Rectum accounts for less than 5% of all cases of Gastrointestinal Stromal Tumours (GIST). Upfront resection in such tumours often leads to a permanent colostomy, significantly impacting patient's quality of life. There is paucity of data regarding the rates of sphincter salvage and optimal duration of neoadjuvant (NA) imatinib required to achieve the same in rectal GIST.
Twenty-three cases of GIST of lower third of rectum were diagnosed at our centre from 2005 till 2015. Histopathology was reported by an experienced gastro-intestinal pathologist. NA imatinib was used in a dose of 400 mg. Response evaluation was done three monthly with a pelvic Magnetic Resonance Imaging and periodic Positron Emission Tomography as indicated. Surgical management was determined by a team of experienced gastrointestinal oncosurgeons. Adjuvant imatinib was used as per standard practice.
Two patients presented with upfront metastatic disease & five underwent upfront surgery. NA imatinib was used in 69.5% (16/23) patients with partial response at six months in 75% (12/16) patients. 19% (3/16) had stable disease. One patient progressed and later received Sunitinib. Median duration of NA therapy was 15 months. Sphincter sparing surgery in the form of intrasphincteric resection (ISR) was possible in 31% (5/16) patients while 43% (7/16) required either an abdominopelvic resection (APR) or Pelvic Exenteration (PE). Three patients had unresectable disease after 12 months of NA imatinib. Response evaluation in one case was awaited. Amongst patients who received six months or less of NA imatinib, two out of four underwent ISR. One patient developed local relapse post ISR. Amongst patients who received more than six months of NA imatinib, 27% (3/11) underwent sphincter sparing surgery & 45% (5/11) required APR or PE. c-KIT gene mutation analysis results were available for five patients. Two patients had wild type, 2 had exon 11 mutation & 1 had exon 13 mutation.
Use of neoadjuvant imatinib lead to sphincter preservation in 31% of patients with GIST of lower third of rectum. Extended neoadjuvant imatinib may not necessarily increase the sphincter preservation rate.
All authors have declared no conflicts of interest.