Supplemental Table 1: Characteristics of high-risk patients undergoing neoadjuvantimatinib(Neo-IM) therapy.
Neo-IM / No Neo-IM / p-valueTotal number / 13 / 21
Follow-up (yrs)
Median / 2.4 / 3.9 / 0.28
Range / 0.01 - 13.1 / 0.7 - 16.4
Sex
Male / 11 / 13 / 0.25
Female / 2 / 8
Age at resection (yrs)
Median / 57 / 58 / 0.64
Range / 23 - 82 / 43- 82
Tumor size (cm) *
Median / 7.1 / 4.5 / 0.79
Range / 2.7 - 9.5 / 0.8 - 21
Distance to AV (cm)
Median / 3 / 4 / 0.11
Range / 0 - 6 / 1 - 8
Presentation
Symptoms / 11 / 14 / 0.43
Exam or endoscopy / 2 / 8
* For patients receiving neoadjuvantimatinib, size was based on pre-treatment imaging.
Supplemental Table 3: Proposed indications for adjuvant imatinib and duration of therapy by margins and risk group
Risk Group/Margins / Adjuvant imatinib / DurationLow risk, R0 / No
Low risk, R1 / Yes / 3 yrs
High risk, R0 / Yes / 3-5 yrs
High risk, R1 / Yes / 5 yrs, consider chronic
Supplemental Figure 1: Oncologic outcome in rectal GIST patients by margin status.
Kaplan-Meier curve is shown depicting local RFS stratified by IM era for all patients. The number of patients at risk is listed for each time point. R2 resections (n=2) were excluded.
Supplemental Figure 2: Algorithm for management of rectal GIST
aFor small GISTs (<3cm) for which local excision (transanal or transabdominal) would be readily possible, we recommend proceeding directly to surgery, with adjuvant imatinib therapy applied as in Supplemental Table 3. For larger rectal GISTs or small ones in which a size reduction would reduce the extent of surgery, we recommend 6 months of neoadjuvantimatinib. Workup includes a CT abdomen/pelvis to rule out synchronous metastasis, although in our institutional experience of 1,000 GISTs, among 128 presenting with synchronous metastasis, none were from a rectal primary (data not shown). MRI of rectum provides more precise assessment of the tumor in relation to adjacent organs, including the anal sphincter muscles.
bHigh rectal GISTs are above the peritoneal reflection or above the second rectal fold. Low rectal GISTs are those accessible transanally either via a traditional transanal approach, transanal minimally invasive surgery (TAMIS), or transanal endoscopic microsurgery (TEM), depending on the surgeon’s preference and expertise.
cFinal determination of local excision and risk of lumen compromise is made at the time of surgery.
dSphincter involvement is determined by digital rectal exam, rectal MRI, or proctoscopy.
eTransabdominal local excision can be accomplished open, laparoscopically, or robotically depending on the surgeon’s expertise. Wide margins are not necessary; instead, a negative margin of 5mm grossly should the goal of the resection.
fLow anterior resection (LAR) should be considered if the tumor involves 50% or more of the rectal circumference. Formal lymphadenectomy with total mesorectal excision is not necessary as lymph node metastasis is extremely rare.
gTransanal local excision can be accomplished with traditional methods, TAMIS, or TEM depending on the surgeon’s preference and expertise. The goal should be a negative margin although a close or even R1 margin may be acceptable in a patient responding to imatinib, if it allows sphincter preservation.
hRadical resection withAPR or TPE may be necessary if sphincter involvement or other involvement of other pelvic organs (respectively) persists after neoadjuvantimatinib. Also, in a patient with poor sphincter function, low LAR or local excision close to sphincters may lead to significant fecal incontinence such that APR would be more appropriate from a quality of life perspective.