What is the Best Workup for Rectal Cancer Staging: US/MRI/PET? Zhen Jane Wang, MD Assistant Professor in Residence UC SF Department of Radiology Disclosure None Acknowledgement Hueylan Chern, MD, Department of Surgery, UCSF Rectal cancer imaging Message: Select patients for sphincter preserving surgery and for neoadjuvant therapy Endorectal US and MRI for local staging CT +/- PET for metastases EUS MRI PET 1
EUS Advantages Office Procedure Inexpensive Minimal preparation Mural depth of invasion Limitations Operator dependent Limited field of view EUS: Normal rectal wall Interface balloon & Mucosa Mucosa & Muscularis Mucosa Submucosa Muscularis Propria EUS staging T1: confined to submucosa EUS staging T1: confined to submucosa T2: invades muscularis propria Muscularis Propria 2
EUS staging EUS staging T1: confined to submucosa T2: invades muscularis propria T3: invades perirectal fat T1: confined to submucosa T2: invades muscularis propria T3: invades perirectal fat EUS staging Seminal vesicle T1: confined to submucosa T2: invades muscularis propria T3: invades perirectal fat T4: invades adjacent organ EUS staging T1: confined to submucosa T2: invades muscularis propria T3: invades perirectal fat T4: invades adjacent organ N1 : + node 3
EUS staging Rectal MRI T staging accuracy: 80-95% Superior in T1 vs. T2 staging Permits FNA of nodes Disadvantages: Limited field of view for lymph nodes and mesorectal fascia visualization Puli et al Ann Surg Oncol 2009;16(2):254 Advantages Improved visualization of anatomy, can see high nodal disease and past stenoses MERCURY trial: high res MRI predicts curative resection vs potential failure Limitation Expensive Limited T1 vs T2 staging Sagittal T2 weighted MRI Rectal MRI Technique Rectal MRI Technique Use a surface coil Endorectal coil not needed IV contrast not necessary Bowel preparation Rectal gel controversial No gel for low rectal cancer Include: Pelvic sidewalls Upper mesorectum Sagittal T2 weighted MRI High resolution (small field of view) T2 weighted images ~3mm slice thickness 0.6-0.8mm in plane resolution Axial /coronal planes orthogonal to the rectal wall To improve T2 vs T3 staging 4
Distance from anal verge T2 w sequence Mucosa/Submucos a Hyperintense Muscularis propria Iso to hypointense MRI T staging T1 from T2 difficult Goal is for T2 and above staging T2: tumor invades muscularis propria T3: tumor invades mesorectum T2 w sequence T2 w sequence 5
Advanced T3 disease (> 5mm invasion) Early T3 disease (< 5mm invasion) Advanced T3 disease (> 5mm invasion) MERCURY trial MR excellent for predicting depth of invasion into the mesorectum and CRM involvement by tumor or nodes Within 0.5mm between MR and histopathology MERCURY Study group, Radiology 2007, BMJ 2006 CRM within 1mm of mesorectal fascia MERCURY trial MR excellent for predicting depth of invasion into the mesorectum and CRM involvement by tumor or nodes Within 0.5mm between MR and histopathology MERCURY Study group, Radiology 2007, BMJ 2006 Coronal T2 image Assess relationship to the sphincter complex to determine feasibility Levator ani of sphincter preserving surgery IS puborectalis ES 6
Assess relationship to the sphincter complex to determine feasibility of sphincter preserving surgery Delineating relationship between anterior peritoneal reflection and tumor Invasion through the peritoneal reflection is T4 Coronal T2 image Sagittal T2 image : nodes T4: tumor invades bladder Axial T2 image Sagittal T2 image Coronal T2 image Size 5mm 68% sensitivity 78% specificity Morphology Spiculated margin Heterogenous signal intensity 85% sensitivity, 97% specificity 7
: nodes -Post CRT Size 5mm 68% sensitivity 78% specificity Morphology Spiculated margin Heterogenous signal intensity 85% sensitivity, 97% specificity MR 66% accurate in the prediction of CRM involvement post CRT Fibrosis difficult to differentiate from tumor infiltration 38% tumor over-staged MR findings of persistent potential CRM involvement associated with higher recurrence Chen et al. Dis Colon Rectum 2005;48:722-728 Sagittal T2 image Diffusion MRI Quantifies water molecule movement Many tumors with restricted diffusion (bright on DWI) Not for depth of extramural spread nor to differentiate between benign and malignant nodes Helpful for node localization and treatment response Rectal MRI Standardized Report 8
PET-CT No role in pre-operative primary tumor staging Helpful in M staging Detection of post-surgical recurrence Intravenous contrast for CT PET-CT: initial staging Brush et al. Health Technol Assess. 2011 PET-CT: initial staging PET-CT: Post-treatment T2 weighted MRI PET 9
PET-CT: Post-treatment RF ablation site RF ablation site PET-CT: Post-treatment PET Patient with colon CA CT peri-rectal lymph node recurrence hepatic metastasis in dome (not seen on CT) Patient underwent radiation Post treatment CT PET-CT: Post-treatment No PET activity at site of recurrence c/w treated tumor new disease or treated disease? PET Fused PET-CT 10
PET false positive Inflammatory uptake of FDG mimicking tumor wait 4 weeks after surgery, 3 weeks after radiotherapy Physiologic uptake of FDG muscle, uterus, corpus luteum cyst correlative CT PET false positive Pre-operative MRI Tumor recurrence? PET false positive PET false positive Tumor recurrence? Seminal vesicle PET scan 11
PET false negative Diabetic patients High circulating glucose compete with FDG Small lesions Resolution limit 5-10mm Mucinous carcinoma Take home messages Ultrasound: T staging MR: T staging Depth of extramural spread, mesorectal involvement, predict CRM involvement Visualizing pelvic side wall / high nodes PET/CT Metastatic disease Recurrence Mucinous adenocarcinoma Thank you! Jane.Wang@ucsf.edu 12