Cancer of the Digestive System

Colorectal Cancer

Digestive System – Anatomy/Physiology

Purpose of digestive system: to change food (nutrients) into energy for storage or body use

Primary Organs: esophagus, stomach, small/large intestine

Other digestive system organs assist in digestion - liver, gallbladder, pancreas

Colon (large intestine), rectum and anus carry waste products (non-nutrients) through to excretion

ADAM and Medline Plus.

• Purpose of colon: Water absorption from indigestible food • Parts of colon in order of passage: ascending, transverse, descending, sigmoid • Ileocecal valve of small intestine passes waste into large intestine at cecum. • Waste excreted from rectum through anal canal - anus

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Large intestine - long hollow organ lined with mucous membrane Muscle wraps around length of large intestine, assisting the passage of food through organ to rectum, anal canal, and anus

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What is Colon Cancer or Colorectal Cancer (CRC)?Disease in which malignant cells form in

tissues of colonColon – first 6 feet of large bowel/intestineRectum – last 6 inches of anal canalAppendix – also a part of colonUsually adenocarcinoma – 95% of all cases

Other typesLymphomaCarcinoid tumorsMelanomsSarcoma

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Epidemiology of CRCThird most common form of cancer in males and

females2nd most common cause of death among US males

and females combined10% of male cancer deaths annually

Greater proportion of cancer deaths - only in lung/bronchus (31%)

10% of female cancer deaths annuallyGreater proportion of cancer deaths - only in

lung/bronchus (26%) & breast (15%)Second leading cause of cancer deaths in Western

world655,000 deaths per year worldwide148,540 will develop annually (2008 estimate)

108,070 in colon; 40,740 in rectum49,960 deaths per year in US

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SymptomsDepends on location of tumor in bowelWhether cancer has metastasizedMany symptoms may also occur in other

diseases, so symptoms are not definitiveThree kinds of symptoms

LocalConstitutionalMetastatic

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Local symptoms (continued)Tumor large enough to fully occlude opening of

bowel – bowel obstructionConstipationAbdominal painTenderness in lower abdomenDistention of abdomenEmesisPerforation and peritonitisLow back pain

AdvancedNoticed on palpationSeen at physical examMetastatic to bladder – blood or air in urineMetastatic to female reproductive organs – vaginal

discharge

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Constitutional Symptoms

Iron deficiency anemia if chronic undetected bleedingFatigueIrregular heart beat - palpatationsPaleness of skinWeight lossDecreased appetiteFever of unknown originThrombosis – usually DVT

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Symptoms of Metastatic CRCUsually spreads to liverJaundiceAbdominal painBile duct obstruction

Pale stools due to biliary obstruction

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Specimen showing one invasive carcinoma – on top, red, irregularly-shaped tumor

Wikipedia

Specimen showing 2 polyps attached by stalk; one invasive carcinoma

Wikipedia

Risk Factors Age over 50

More than 90% of CRC diagnosed in those > 50 yearsMost CRC appears in 60s and 70sCases under 50 rare unless genetic predisposition among younger

family membersAA highest rate of all racial/ethnic groups in US; Eastern European

Jews History of cancer

Women with previously diagnosed/treated ovarian, uterine, or breast cancer

Personal diagnosis and treatment for CRCHistory of polyps, especially benign polyps - adenomatous

Inflammatory bowel disease – History of chronic ulcerative colitis in 1%; Chron’s

Obesity Heavy alcohol use Family History

Less than 10% caused by geneticsClose relative diagnosed before 55 years of ageMultiple relatives diagnosed with CRC

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Risk Factors (continued)Smoking

Smokers more likely to die of CRC than non-smokersFemale smokers more than 40% more likely to die of

CRC than non-smokersMale smokers – increased risk (30%) compared to

non-smokersDiet low in fruits/vegetables, fish, poultry - possible

Unclear fiber effectDiet high in fat, red and/or processed meat -

possiblePhysical inactivityVirus – HPVLow levels of selenium

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PreventionDeath rate dropped in last 15 yearsTakes many years to develop CRCEarly detection of polyps and CRC – criticalMost CRC develops from easily removable

polypsUndetected polyps grow through lining and layer of

colon wall and rectumEarly screening could significantly reduce

mortalityScreening rates low Almost all men and women older than 50 should

screen

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Diagnosis and ScreeningInitial DRE – inspection of distal parts of rectumFOBT – tests for trace amounts of blood in stool -

annuallyGuiac (chemical)Immunochemical – superior to FOBTMust be used with endoscopyFalse negatives and positives

EndoscopySigmoidoscopy – inspection of rectum & lower third of

colon with lighted probe and inserting air – every 5 years

Colonoscopy – inspection of rectum and all parts of colon; polyp removal and biopsy – every 3 years

Double contrast barium enema for detection in large intestine

Complete blood count to check for anemia

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All 4 screening tests - effective in detecting cancers in early stages.

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PrognosisDepends on stage of cancer when detectedIf detected and treated early, most patients

survive for 5 years 5-year survival rate drops if not detected

early enough and cancer has metastasizedIf CRC does not return in 5 years,

considered curedStages 1-3 potentially curableStage 4 not curable in most cases

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Staging• Depends on size of tumor and degree of

penetration• Stage 0 – very early – tumor on mucosa – inner-

most colon layers• Stage I: Metastasized into sub-mucosa – inner

layers• T1N0M0 – In sub-mucosa - inner layers of the colon • T2N0M0 – in muscularis propria

• Stage II: Metastasized into colon’s muscle wall • A-T3N0M0 - In sub-serosa or beyond (no organs)• B-T4N0M0 – in adjacent organs after perforates peritoneum

• Stage III: Metastasized into nearby lymph nodes• A -T1-2N1M0 – in 1-3 regional lymph nodes (T1 or T2)• B- T3-4 N1M0 – in 1-3 regional lymph nodes (T3 or T4)• C-Any T, N2M0- 4 or more regional lymph nodes. Any T

• Stage IV: Metastasized to remote organs • Any T, Any N, M1 – remote metastases. Any T, any N

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Several metastatic tumors in liver and spleen originating from carcinoma of intestine

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Cancer of large bowel (sigmoid area of colon) detected on barium enema

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Cancer of the rectum detected with barium enema.

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TreatmentDepends on stage of cancerChoices:

Surgery – primary treatmentRadiation (mostly used in Stage 3 rectal

cancer); also used with chemotherapy in other stages

Treatment by stageStage 0 – removal during colonoscopyStage 1, 2, 3 – more extensive surgeryStage 4 – chemotherapyMetastatic liver cancer: surgery,

chemotherapy/radiation directed to liver, cryotherapy, ablation

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