CT COLONOGRAPHY

CRC TRENDS  Incidence decreased by 7%  Mortality decreased by 20%  Five year survival rates increased by 12%

COLORECTAL CANCER  Lifetime risk for development 5% or 1:19  Lifetime risk for death : 2.5%  Males slightly higher than females  75% in average risk patients

LIMITED IMPACT Only 37% of cases are diagnosed when the disease is localized 20% will have distant metastases at initial diagnosis

RISK FACTORS  Age > 50 years ((90%)  Familial factors: FAP, Gardner’s, Ashkenazi Jews(APC gene), HNPCC  Racial group : African  Personal or family hx : CRC 2-4x or adenomatous polyp  Personal hx: ovarian, endometrial or breast cancer, chronic IBD > 10 years(UC>Crohn’s)

CRC RISK FACTORS  Low fiber, high fat diet  High red meat consumption  Inactivity, obesity  Smoking  Alcohol

CHEMO-PREVENTION OF CRC  Aspirin, NSAIDS  Postmenopausal estrogen  Calcium, Selenium  Vitamins A, C, E and folic acid

ANATOMIC LOCATION OF CRC Rectosigmoid: 52-61% Ascending colon and cecum 19-24%

SCREENING TESTS FOR CRC How accurate are they?

FIT ADVANTAGES No dietary restrictions Safe, non-invasive, no bowel prep Inexpensive Best study regarding impact on mortality Fewer false positives from upper GI bleed Sensitivity FIT vs gFOBT 82% vs 64% for colorectal cancer 30% vs 41% for adenomatous polyps

FIT DISADVANTAGES  Most cancers bleed intermittently  Most adenomas don’t bleed  non-neoplastic : hemorrhoids, NSAID

COLONOSCOPY High sensitivity and specificity Sensitivity < 5 mm 73% 6-9 mm 87% > 10mm 94% Gold standard for colon evaluation. For an average risk individual with a negative colonoscopy, further screening of any type is not required for 10 years.

COLONOSCOPY- LIMITATIONS  Variable patient compliance  Requires IV sedation  Costly  Time-consuming  Incomplete in 5-10%  CRC localization accuracy 86%

INCOMPLETE COLONOSCOPY  Operator inexperience  Poor bowel cleansing  Redundant bowel  Benign/malignant stricture  Severe diverticulosis

COLONOSCOPY COMPLICATIONS  Perforation dx 1/1000 tx 1/500  Bleeding 3/1000  Death 1-3/ Death rate from colon cancer in yo is 1.8/10000

PERFORATION RATES DCBE 1/25000 CTC 1/22000 FLEX SIGMOIDOSCOPY 1/10000 DIAG COLONOSCOPY 1/1000 THERAPEUTIC COLONOSCOPY 1/500

2009 ACR/CAR GUIDELINES Indications 1) (screening) exam 2) surveillance exam 3) diagnostic exam 4) following incomplete colonoscopy 5) patients at risk for colonoscopy: sedation risk, anticoagulant therapy, prior incomplete colonoscopy, advanced age.

CTC PRO  minimally invasive  low complication rate (perforations 0.46 per 10,000) compared to colonoscopy  no sedation used  usually effective where colonoscopy is technically incomplete  also images extraluminal structures

CTC CON  discomfort  radiation exposure  reduced sensitivity for detection of flat polyps and polyps <6 mm  does not permit biopsy or polyp removal  the accuracy depends on expertise of the radiologist and adequacy of preparation  there are currently no outcome studies regarding CRC mortality prevention

RADIATION  Fixed KVp at 120kv but mA varies  Linear relationship between mA and patient dose  Ultra - low dose ie 10-80mA adequate for colon  Symptomatic patients increase mA for evaluation of extra-colonic findings  Colon ca staging use normal 220 mA for complete exam

2009 ACR GUIDELINES ABSOLUTE CONTRA-INDICATIONS 1. routine f/u of IBD 2. hereditary polyposis or non-polyposis syndromes 3. evaluation of anal disease 4. pregnant patients

2009 ACR GUIDELINES RELATIVE CONTRAINDICATIONS 1. symptomatic acute colitis 2. acute diarrhea 3. recent acute diverticulitis 4. symptomatic colon containing hernia 5. symptomatic or high grade SBO 6. recent colorectal surgery 7. deep biopsy or polypectomy 8. colon perforation

TECHNIQUE Supine and prone imaging Sometimes decubitus IV buscopan Co2 insufflation

BUSCOPAN CONTRA-INDICATIONS  Myastenia gravis  Untreated narrow angle glaucoma  Prostate hypertrophy with urinary retention  Stenotic lesions of the GI tract Megacolon  MI within past 6 months  Tachycardia and angina Congestive cardiac failure

The primary goal of CTC is to detect the precursor lesion of colorectal malignancy

POLYPS 4 types Benign neoplastic ie adenoma Non- neoplastic ie hyperplastic,inflammatory, hamartomatous Only 3% of adenomas will progress to malignancy 30-40% develop an adenoma by 60 yrs

ADENOMATOUS POLYPS Dysplasia- mild, moderate, severe or high grade 3 histologic types: Tubular 85%, < 10mm Tubulovillous 10%, >10mm Villous 5%, 10x increased chance malignancy than tubular, 75%>20mm

ADENOMA-CA PATHWAY Ca risk increases with increasing size of polyp <1% 6-9mm polyp 10% mm polyp 10-50% >20mm polyp

RECOMMENDATIONS BCRS >10mm size - 10% chance malignancy >20mm - 50% chance of malignancy = colonoscopy 6-9mm - f/u CTC in 3 years, 0.7% cancer risk (not warranting colonoscopy/biopsy) if 3 polyps found between 6-9mm size, risk malignancy is equivalent to 10mm polyp ie 10% needs colonoscopy polyps less than 6mm size should not be reported, <0.1% risk malignancy

TUBULOVILLOUS ADENOMA. (A) ENDOLUMINAL 3D VIEW FROM CT COLONOGRAPHY SHOWS A 10- MM PEDUNCULATED POLYP WITH A WELL-DEFINED STALK. (B) AXIAL 2D VIEW SHOWS THE SAME PEDUNCULATED POLYP (ARROWHEAD). UNLIKE MOST OTHER PEDUNCULATED LESIONS, WHICH ARE MORE EASILY RECOGNIZED AS SUCH ON 3D VIEWS, THE STALK AND POLYP IN THIS CASE HAPPEN TO BE ALIGNED IN A STANDARD 2D PLANE.

TUBULOVILLOUS ADENOMA. (A) ENDOLUMINAL 3D VIEW FROM CT COLONOGRAPHY SHOWS A SESSILE, LOBULATED 20-MM POLYP EXTENDING FROM A COLONIC FOLD. (B) DIGITAL PHOTOGRAPH FROM OPTICAL COLONOSCOPY SHOWS THE SAME LOBULATED LESION.

VILLOUS ADENOMA. (A) ENDOLUMINAL 3D VIEW FROM CT COLONOGRAPHY SHOWS A 5-CM IRREGULAR CECAL MASS. THIS PAPILLARY APPEARANCE IS HIGHLY SUGGESTIVE OF A VILLOUS TUMOR. (B) AXIAL 2D IMAGE (WITHOUT ELECTRONIC CLEANSING OF OPACIFIED FLUID) SHOWS THE SAME IRREGULAR CECAL MASS (ARROWHEADS). (C) DIGITAL PHOTOGRAPH FROM OPTICAL COLONOSCOPY SHOWS THE PAPILLARY, FRONDLIKE NATURE OF THE MASS TO GREATER ADVANTAGE. THE LESION WAS NOT MALIGNANT DESPITE ITS LARGE SIZE.

MALIGNANT POLYP. ENDOLUMINAL 3D VIEW FROM CT COLONOGRAPHY IN A SYMPTOMATIC PATIENT SHOWS A LARGE SESSILE MASS, WHICH PROVED TO BE MALIGNANT.

INVASIVE ADENOCARCINOMA. (A) CONTRAST MATERIAL-ENHANCED 2D CURVED REFORMATTED IMAGE WITH SOFT-TISSUE WINDOWING SHOWS AN ANNULAR- CONSTRICTING MASS WITH SHOULDERING (ARROWHEADS) INVOLVING THE SIGMOID COLON. CROSS-SECTIONAL 2D VIEWS ARE MUCH MORE EFFECTIVE THAN ENDOLUMINAL DISPLAYS FOR DEPICTING INVASIVE MASS LESIONS. (B) DIGITAL PHOTOGRAPH FROM OPTICAL COLONOSCOPY SHOWS THE PROXIMAL ASPECT OF THE MASS.

HYPERPLASTIC POLYP. (A) ENDOLUMINAL 3D VIEW FROM CT COLONOGRAPHY SHOWS A 7-MM SESSILE SOFT-TISSUE LESION, WHICH IS INDISTINGUISHABLE FROM AN ADENOMATOUS POLYP. (B) DIGITAL PHOTOGRAPH FROM OPTICAL COLONOSCOPY SHOWS THE SAME SESSILE POLYP. RELIABLE DISTINCTION FROM AN ADENOMATOUS POLYP REQUIRES HISTOLOGIC ANALYSIS.

INTERNAL HEMORRHOIDS. (A) ENDOLUMINAL 3D VIEW FROM CT COLONOGRAPHY SHOWS A LARGE, CIRCUMFERENTIAL MASS AT THE ANORECTAL JUNCTION THAT SURROUNDS THE RECTAL CATHETER. (B) DIGITAL PHOTOGRAPH FROM OPTICAL COLONOSCOPY SHOWS INTERNAL HEMORRHOIDS, WHICH ARE AT LEAST PARTIALLY THROMBOSED, SURROUNDING THE COLONOSCOPE.

SIDE-BY-SIDE COMPARISON OF (INWARD) POLYP AND (OUTWARD) DIVERTICULUM. ENDOLUMINAL 3D VIEW FROM CT COLONOGRAPHY SHOWS A 16-MM TUBULAR ADENOMA (ARROW) ADJACENT TO A WIDE- MOUTH DIVERTICULUM (ARROWHEAD). THE VOLUME RENDERING AND LIGHTING DISPLAY USED HERE ALLOW FOR EASY DISTINCTION.