Colorectal CancerColorectal Cancer

Colorectal CancerWorldwide, colon and rectum cancer is the third most common cancer Worldwide, colon and rectum cancer is the third most common cancer

andand it is it is the most common GI cancer. the most common GI cancer.

The vast majority of colorectal cancers are adenocarcinomasadenocarcinomas, which arise from preexisting adenomatous polyps that develop in the normal colonic mucosa.

Of patients with colon cancer, 90% are older than 50 years. The highest rates of incidence are in individuals aged 70-85 years. Only 5% of patients are younger than 40 years.

The overall 5-year survival rate from colon cancer is approximately 60% but it is different for each stage. For Dukes stage A tumors involving only the mucosa, the 5-year survival rate exceeds 90%, whereas for metastatic

colon cancer, the 5-year survival rate is about 5%.

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Colorectal Cancer

The highest incidence rates are in North America, Australia/New Zealand, Western Europe, and, in men especially, Japan.

Incidence tends to be low in Africa and Asia and intermediate in Eastern Europe and southern parts of South America.

From: Global Cancer Statistics, 2002 -- Parkin et al_ 55 (2) 74 -- CA A Cancer Journal for Clinicians

Colon and rectum cancers Colon and rectum cancers accounted for about accounted for about 1 million1 million

new cases in 2002 new cases in 2002

In the US:

Colorectal cancer is the third most Colorectal cancer is the third most common malignant neoplasm worldwidecommon malignant neoplasm worldwide and the second leading cause of cancer and the second leading cause of cancer deaths in the United States.deaths in the United States.

It is estimated that there will be 145,290 new cases diagnosed in the United States in 2005 and 56,290 deaths due to this disease.

Colorectal Cancer

Sex: The frequency of colon cancer is essentially the same among men and women.

Colorectal Cancer

• The most common sites are the rectumrectum (34%) and sigmoidsigmoid (25%). • Over the 20 years, the incidence of cancer in the cecum increased and

that in the rectum decreased. • Cecal, ascending, and transverse colon cancers accounted for 34% of

lesions - all beyond the range of the flexible sigmoidoscope. all beyond the range of the flexible sigmoidoscope.

Spatial Distribution:

Clinical Presentation:

• Colon cancer often is found by screening and may be completely asymptomatic. • Approximately 50% of patients present with abdominal pain, • 35% with altered bowel habits, • 30% with occult bleeding, • 15% with intestinal obstruction. • Right-sided colon cancers tend to be larger and more likely to bleed, whereas

left-sided tumors tend to be smaller and more likely to be obstructing.

Colorectal CancerPreferred Examination:

• Begin the evaluation with a history and physical

examination, including a digital rectal examination. • Inspect the stool and test for occult blood. • Perform blood tests, including a full blood count, liver function tests, and

carcinoembryonic antigen level. • Perform either a sigmoidoscopy (rigid or flexible) and a double-contrast

barium enema or a colonoscopy • Virtual colonoscopy, a new experimental test to evaluate the entire colon

Double-contrast barium enemas are an option for screening for colorectal Double-contrast barium enemas are an option for screening for colorectal

cancer and can aid in establishing the diagnosis of colon cancer.cancer and can aid in establishing the diagnosis of colon cancer.

Double-contrast barium enema detects approximately 90%90% of colonic tumors.

Colorectal Cancer

Double-contrast study:

Most colonic cancers are relatively advanced, measuring 3-4 cm in diameter at diagnosis. The appearances of the tumors on double-contrast barium enema reflect the 3 morphologic types: polypoid,

annular, or flat.

• Polypoid lesionsPolypoid lesions vary from small smooth tumors to larger lobulated masses with an irregular surface and an associated contour deformity along 1 margin of the bowel wall.

• Annular lesionsAnnular lesions result from irregular circumferential masses that severely constrict the bowel lumen. The margins of the carcinoma show overhanging edges, the tumor shelf or shoulder (termed "apple-core" lesion). The mucosal folds in the narrowed segment are destroyed; ulceration may be present

• Flat lesionsFlat lesions, which are rare, are visualized as a unilateral broad-based contour defect. Ulceration may be present

Colorectal CancerDouble-contrast study:

From: http://www.kgan.minami.fukuoka.jp

Polypoid carcinoma. Polypoid carcinoma.

A large, irregular lobulated mass is present in the rectosigmoid junction.

Typical annular carcinomaannular carcinoma of the transverse colon

Colorectal CancerDouble-contrast study:

From: http://www.kgan.minami.fukuoka.jp

Colorectal CancerDouble-contrast study:

"apple-core" lesion

Annular carcinoma of the sigmoid colon. The lumen of the sigmoid is narrowed severely by the circumferential mass with mucosal destruction and the overhanging

edges or shouldering at the tumor margins.

Colorectal CancerDouble-contrast study:

From: http://www.kgan.minami.fukuoka.jp

Flat carcinomaFlat carcinoma of the sigmoid colon - a unilateral broad-based contour defect.

Colorectal CancerCAT SCAN

Indications for CT scanIndications for CT scan

• CT scan is used for staging colonic carcinomastaging colonic carcinoma prior to surgery, for

assessing and staging recurrent disease, and for detecting the presence

of distant metastases. • Preoperative CT scan is indicated if distant metastases or local invasion of

adjacent organs or abdominal wall are suggested clinically. • In older patients who may be unable to undergo colonoscopy or barium

enema, modified CT scan may be performed for primary detection of

colorectal tumors.

Colonic tumors may be diagnosed on CT scan as an incidental finding.Colonic tumors may be diagnosed on CT scan as an incidental finding.

Colorectal CancerCT CT FindingsFindings

• A localized tumor may be seen on CT scan as an intraluminal or intramural intraluminal or intramural

mass of soft tissue densitymass of soft tissue density adjacent to the gas-filled or contrast-filled bowel

lumen.

• More advanced tumors are associated with thickening of the bowel wall (>6

mm) and infiltration of the pericolic fat.

• Annular carcinomas are detected by a thickening of the bowel wall and

narrowing of the lumen. This thickening is concentric if the scanning plane

is at right angles to the long axis of the bowel.

• Extracolonic tumor spread is indicated by a loss of tissue fat planes

between the colon and surrounding structures

• Tumors less than 2 cm in diameter cannot be detected reliably by the Tumors less than 2 cm in diameter cannot be detected reliably by the

standard CT scan technique. standard CT scan technique.

Colorectal Cancer

CT Scan Staging System For Colonic Cancer

Stage Description

T1 Intraluminal polypoid mass; no thickening of bowel wall

T2 Thickened colonic wall >6 mm; no periodic extension

T3a Thickened colonic wall plus invasion of adjacent muscle or organs

T3b Thickened colonic wall plus invasion of pelvic side wall or abdominal wall

T4 Distant metastases, usually liver, lung or adrenal

modified from Thoeni

N staging

Nodes greater than 10 mm in diameter are considered abnormal.Nodes greater than 10 mm in diameter are considered abnormal.

M Staging

Hepatic metastases are the most common site of distant spread. Hepatic metastases are the most common site of distant spread.

Other common sites include the lungs, adrenals, peritoneum, and omentum.

Colorectal CancerCT Findings

Preoperative CT – colon wall thickening and infiltration of

the pericolic fat

Colorectal CancerCT Findings

Numerous metastases. The tumor cells were arranged

in nodules and occupied approximately 90% of the

hepatic parenchyma. Contrast-enhanced CT showing liver metastases.

Several low-density metastases involve both lobes of the liver.

Colorectal Cancer

CT Findings – CT colonographyCT colonography

• CT scan colonography or virtual colonoscopy was introduced in 1996 as

a screening tool for the detection of colorectal polyps and small a screening tool for the detection of colorectal polyps and small

cancers. cancers. • It involves a 3-dimensional computer reconstruction from a volumetric

data set using a workstation as well as distending a clean colon with air. • Images are read as soft copy from the workstation using a combination

of paging-through the 2D axial images, aided by multiplanar and 3D

endoluminal images.

The sensitivity of this technique is greater than that of the double-

contrast barium enema. For polyps larger than 10 mm, it has a

sensitivity of 91%91% but a specificity of 76%76%. This sensitivity falls to 81%81%

for 5-10 mm polyps.

Colorectal Cancer

CT Findings – CT colonography

The recent arrival of

multisectional helical scanners

has reduced the time required to

obtain the images (usually 30

seconds for each series,

scanning the patient prone and

supine using a reduced tube

current to minimize the radiation

dose).

Colorectal Cancer

CT Findings – CT colonography

Colorectal Cancer

CT Findings – CT colonography

Colorectal CancerUltrasound

• The primary role of ultrasound (US) in patients with colonic cancer is the detection of hepatic metastasesdetection of hepatic metastases.

• US has a detection rate of 70-90% for hepatic metastases.

Colorectal CancerMRI

• MRI provides greater contrast between soft tissues than CT scan.

• Colonic tumors have low signal intensity (similar to adjacent skeletal

muscle) on T1-weighted sequences, which facilitates their

differentiation from high-signal perirectal fat.

• T2-weighted images are used to detect pelvic sidewall invasion. T2-weighted images are used to detect pelvic sidewall invasion.

• MRI and CT scan have a similar overall accuracy (approximately 60%)

in the detection of enlarged lymph nodes (N staging) and liver

metastases (M staging).

• MRI has a higher sensitivity (91%) than CT scan (82%) in detecting

local recurrence and a higher specificity (100%) than CT scan (69%).

Colorectal CancerPET

Findings:

• Nuclear medicine has a small peripheral role in colonic cancer.

• Consider using radioimmunoscintigraphy with monoclonal antibody that

recognizes carcinoembryonic antigen (CAA) or tumor-associated

glycoprotein-72 to detect disease recurrencedisease recurrence in the pelvis or extrahepatic

abdomen.

• Consider using positive emission tomography (PET) with 2F 18-fluoro-

deoxy-D-glucose (FDG) to detect recurrent disease.

Colorectal Cancer

HistoryA 70-year-old male with hx of colorectal CA s/p resection, chemo and XRT. Recently with rising CEA levels and CT with indistinguishable soft tissue density in pelvis.

PET/CT FindingsUptake in soft-tissue mass plus an additional metastatic lesion in sacrum.

From: http://www.petscaninfo.com/

PET/CT

Colorectal Cancer - Screening

• Between 70 and 90 percent of colorectal

cancers arise from adenomatous polypsadenomatous polyps,

and 10 to 30 percent arise from sessile sessile

adenomasadenomas.• The larger the polyp, the greater the potential

for malignancy. • Diminutive polyps (5 mm or less in diameter)

have a negligible malignant potential. • Polyps with a diameter of 5 to 10 mm are

considered small, whereas polyps greater

than 10 mm in diameter are considered large.• Polyps larger than 2 cm in diameter have Polyps larger than 2 cm in diameter have

a 50 percent chance of becoming a 50 percent chance of becoming

malignant over time. malignant over time.

Prevention and Screening MethodsPrevention and Screening Methods 1.5 cm bi-lobed benign tubular adenoma on a stalk.

Sessile villous adenoma

Colorectal Cancer - Screening