Rectal Cancer: Local Staging, Re-staging and Assessment of Lymph Node Metastases Using PET-CT, CT-Perfusion and 3T MRI: A Prospective Feasibility Study
30 consecutive patients with histologically-proven, non-mucinous rectal cancer will be
recruited and stratified into three separate groups as follows:
- T2 tumors (requiring only surgery)
- Early T3 tumors (requiring preoperative standard course radiation therapy)
- Advanced T3 and T4 tumors (requiring preoperative chemoradiation)
The pretreatment imaging studies will be performed with a 3T MRI pelvis,PET-CT and
CT-Perfusion of the pelvis. The patient will then receive standard treatment consisting of
surgery,radiation therapy or a course of neoadjuvant chemoradiation.For patients with T3 and
T4 tumors, repeat imaging using all three modalities outlined above will be performed
Histopathology & data analysis
All patients will be examined on a 3-T MRI unit (Siemens Medical, Germany) at St. Joseph's
The MRI protocol is as follows:
- Buscopan 40 mg IM/IV prior to study
- Axial T2 TSE of the entire pelvis (aortic bifurcation to pubic symphysis)
- Sagittal T2 TSE (240 cm FOV) for detection of the rectal tumor
- Axial oblique T2 TSE (220 cm FOV) perpendicular to the rectal tumor
- 3 mm slice thickness
- Coronal T2 TSE (220 cm FOV)
- Axial DWI (B values 0, 500, 1000)
- ADC map
Unless otherwise specified, slice thickness is 4mm. Technique is free-breathing; no bowel
preparation, intraluminal or intravascular contrast agents are administered.
- Patient fasts for 6-12 hours prior to study, depending on timing of scan
- Patients to be scanned in the morning will fast overnight; those being scanned in the
afternoon will fast for 6 hours following a light breakfast.
- Blood sugar level measurement prior to study (should be less than 11 mmol/L). Insulin
dependent diabetics are scanned in the early afternoon following a light breakfast and
routine morning insulin.
- Exclude pregnancy with urine/serum hCG
- Intravenous injection of 5MBq/kg of F-18 FDG)
- Intravenous injection of 20 mg Lasix, 10 minutes following F-18 FDG injection
- IV hydration with 250-500 mL of saline
- 60 minutes post-injection, acquire non contrast CT and positron emission tomography
imaging of the pelvis
CT Perfusion Protocol:
All patients will undergo CT Perfusion with a 64-slice CT scanner (Discovery CT750 HD, GE
Healthcare) at St. Joseph's Health Care, London.
The protocol is as follows:
- Preliminary non-contrast 2.5-mm-thick helical CT of the pelvic region (from the aortic
bifurcation to the symphysis pubis) with free-breathing to locate a 8-cm section of the
rectal tumor that was imaged in the MRI study.
- Prescribe a CT Perfusion study using the axial shuttle mode on the 8-cm section
identified above. The perfusion study consists of two phases. The selected pelvic
section is scanned every 2.8 s for 64.4 s (24 times) in the first phase and every 15 s
for the next 120 s (8 times) in the second phase. The total duration of scanning is
184.4 s. The scanning parameters for both phases are: 120 kVp, 125 mA, 0.4 s rotation
period, and 5 mm thick slices. All dynamic images will be reconstructed with adaptive
statistical iterative reconstruction (ASIR) technique to reduce noise.
- Contrast injected at a rate of 3-4 ml/s will start at the same as the two-phase
scanning, to allow for acquisition of 3-4 baseline volumes (before contrast arrives in
- Free-breathing is allowed during scanning.
- Contrast dose is 0.8ml/kg of body weight up to maximum of 70 ml of contrast at a
concentration of 370 mg iodine/ml.
- The acquired dynamic contrast enhanced (DCE) images will be analyzed by CT Perfusion
(GE Healthcare) to determine blood flow, blood volume, mean transit time and capillary
permeability surface area of the tumor.
Surgical Resection and histopathological examination:
- Total mesorectal excision as per standardized surgical technique; orientation of
surgical specimen according to pre-established regional lymph node map -Mapping of
regional lymph nodes by pathologist into perirectal zones (anterior, posterior, left,
right, superior, middle, inferior)
- Compare pre- and post-therapeutic imaging with histopathological findings.
Endpoint Classification: Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Diagnostic
efficacy of PET, CT-perfusion and MRI to stage patients with rectal cancer
The patient will undergo imaging studies with PET, CT-perfusion and MRI before and after standard preoperative chemoradiation and these imaging studies will be compared with standard imaging and with the final pathology specimen in order to determine the accuracy of these 3 studies in detecting lymph node metastases and response of the primary tumour to treatment
Barbara J Fisher, MD
University of Western Ontario, Canada
Canada: Health Canada