CA RECTUM

Dr. Manish Dutt

• Anatomy• Epidemiology & etiology• Presentation• Pathology• Staging• Diagnostic workup• Prognostic factors

Anatomy• 12-15 cm from anal

verge.

• Diameter– 4 cm (upper part)– Dilated (lower

part)

• Begins at the rectosigmoid junction, at level of third sacral vertebra

• Ends at the anorectal junction, 2-3 cm in front of and a little below the coccyx

• Divided into 3 parts• Upper third-(8 to 10, to 12 to 15 cm

from the anal verge)• Middle third-(5 to 6 to 8 to 10 cm from

the anal verge)• Lower third-(3 to 6 cm from the anal

verge)

• 3 distinct intraluminal curves ( Valves of Houston

• Superior 1/3rd of the rectum– Covered by peritoneum on the

anterior and lateral surfaces but is retroperitoneal posteriorly without any serosal covering.

• Middle 1/3rd of the rectum– Covered by peritoneum on the

anterior surface• Inferior 1/3rd of the rectum– Devoid of peritoneum– Close proximity to adjacent structure

including boney pelvis.

Peritoneal Relations

Arterial supply• Superior rectal A – fr. IMA; supplies

upper and middle rectum• Middle rectal A- fr. Ant div. of Internal

iliac A. (supplies lower rectum)• Inferior rectal A- fr. Internal pudendal

A.• Median sacral artery – from aorta ..

Supplies anorectum

Venous drainage Internal rectal venous

plexusSuperior rectal V( upper & middle third rectum)inf. Mesentric vein

Middle portion of external rectal venous plexus Middle rectal V- lower rectum and upper anal canalant. Div. of internal iliac

Inferior portion of external rectal venous plexus Inferior rectal vein( lower anal canal)internal pudendal vein

Lymphatic drainage

• Upper and middle rectum– Pararectal lymph nodes, located

directly on the muscle layer of the rectum

– Inferior mesenteric lymph nodes, via the nodes along the superior rectal vessels

• Lower rectum– Sacral group of lymph nodes or

Internal iliac lymph nodes

• Below the dentate line – Inguinal nodes and external iliac

chain

EPIDEMIOLOGY• Colorectal cancer- 3rd mc cancer in

men ,2nd in women (app. 10% of all cancers)

• 2/3rd of cases occur in the colon and 1/3rd in the rectum

• 2nd mcc of cancer mortality• 55% of cases in more developed regions•  highest rates in Australia/New Zealand

(ASR 44.8 and 32.2 per 100,000 in men and women, and the lowest in Western Africa (4.5 and 3.8 per 100,000]

•  highest mortality in Central and Eastern Europe (20.3 per 100,000 for men, 11.7 per 100,000 for women), and the lowest in Western Africa (3.5 and 3.0)

INDIAN STATISTICS• Annual incidence rates (AARs) for rectal cancer in men is 4.1

and 3.5 per 100,000 in women.• Rectal cancer ranks 9th among men in india.• In the 2013 report, the highest AAR in men for CRCs was

recorded in Thiruvananthapuram (4.1) followed by Banglore (3.9) and Mumbai (3.7) . The highest AAR in women for CRCs was recorded in Nagaland (5.2) followed by Aizwal (4.5)

• The projected incident number of rectal cancer in India for 2016 has been estimated to be 22,317 cases (Murthy, 2009).

• Cecum 14 %• Ascending colon 10 %• Transverse colon 12 %• Descending colon7 %• Sigmoid colon 25 %• Rectosigmoid junct 0.9 %

• Rectum 23 %

ETIOLOGY• 75% of colorectal cancers are sporadic, • 15%to 20% develop in those with either a positive

family history or Personal history of colorectal, ovary, endometrial or breast cancer.

• genetic predisposition- such as hereditary nonpolyposis colorectal cancer (HNPCC) (4% to 7%)

• familial adenomatous polyposis (FAP) (1%)• inflammatory bowel disease, particularly chronic

ulcerative colitis (1%).

• Age and gender-older men( 70)• Race and Ethnicity-Ashkenazi Jews, African Americans• smoking• High-fat diet, High-caloric diet & obesity• fried, barbecued, and processed meats(pork)• Excess alcohol consumption( folate metab. And

acetaldehyde)• Diabetes( insulin resistance)• Sedentary lifestyle • Inflammatory bowel disease-Ulcerative colitis

PROTECTIVE

• High-fiber diet[dilute faecal carcinogens, decrease colon transit time]

• Antioxidant vitamins• Fresh fruit/vegetables• NSAIDS & COX-2 inhibitors[ in lynch synd.]• Decaffeinated coffee.• High calcium and Magnesium [ binds bile acids]• Vit D & bisphosphonates[ inhibit cell

proliferation, inc. apoptosis

Pathological features• The majority (>90%) of

colorectal cancers are adenocarcinomas.

• Mucinous(Colloid cancer)( 15-20% of adenoca)

• Signet ring cell (1-2% of adenoca)

• Adenosquamous carcinoma

• Rare(include carcinoid tumors,leiomyosarcomas,lymphomas and squamous cell cancers

Tis T1 T2 T3 T4

Extension to an adjacent organ

MucosaMuscularis

mucosae

Submucosa

Muscularis propria

Subserosa

Serosa

Prognostic factors• pathologic extent of disease

as determined by the degree of bowel wall penetration by the tumor(T stage)

• presence or absence of lymph node metastases(N stage)

• distant metastases.• Tumor differentiation• CEA level at the time of

presentation.

Good prognostic factors Old age Gender(F>M) Asymptomatic pts Polypoidal lesions Diploid

Poor prognostic factors Obstruction Perforation Ulcerative lesion Adjacent structures involvement Positive margins LVSI Signet cell carcinoma High CEA(>100ng/ml)

Stage and Prognosis

Stage 5-year Survival (%)

0,1 Tis,T1;No;Mo > 90I T2;No;Mo 80-85II T3-4;No;Mo 70-75

III T2;N1-3;Mo 70-75III T3;N1-3;Mo 50-65III T4;N1-2;Mo 25-45IV M1 <3

CLINICAL PRESENTATION• Symptoms

– Usually symptomatic– gross red blood (mixed or covering stool accompanied by the passage of

mucus)– Change in bowel habit (diarrhoea, constipation, narrow stool– urgency, inadequate emptying, and tenesmus .(cicumfrential penetrating)– Urinary symptoms and buttock or perineal pain from posterior extension

Sciatic pain is indicative of tumor invasion into the sciatic notch,.– Abdominal discomfort (pain, fullness, cramps, bloating, vomiting).– Weight loss, tiredness.

• Acute Presentations– Intestinal obstruction.– Perforation.– Massive bleeding

SIGNS• Pallor• Abdominal mass• PR mass• Ascites

– Rectal metastasis travel along portal drainage to liver via superior rectal vein as well as systemic drainage to lung via middle inferior rectal veins.

Diagnostic Workup• History—including family history of colorectal cancer or polyps• Physical examinations including DRE : size, location,

ulceration, mobile vs. fixed, distance from anal verge and sphincter functions.

• Proctoscopy—including assessment of mobility, minimum diameter of the lumen, and distance from the anal verge,circumferential assesment

• Routine investigation– Complete blood count, KFT, LFT– Chest X-ray

• Baseline CECT chest, abdomen, pelvis• MRI and EUS• CEA: High CEA levels associated with poorer survival• Biopsy of the primary tumor

Pathologic stage evaluation

• Grade• Depth of penetration(T)• Number of LN evaluated (12)and positive• Margins( prox, distal, CRM)• Neoadjuvant treatment effects(0-3)• PNI& LVI• extranodal tumor deposits

Colonoscopy or barium enema

Figure: Carcinoma of the rectum. Double-contrast barium enema shows a long segment of concentric luminal narrowing (arrows) along the rectum with minimal irregularity of the mucosal surface.

To evaluate remainder of large bowel to rule out synchronous tumor or presence of polyp syndrome.

Transrectal ultrasound –EUS

• 75-95% accurate in T staging• 62-83% accurate in mesorectal lymph node

staging• 20% overstaging & 10% understaging• good at demonstrating 5 layers of rectal

wall, irrigation used to enhance images.• Not after preop chemo or RT.• Use is limited to lesion < 14 cm from anus,

not applicable for upper rectum, for stenosing tumor

• Very useful in determining extension of disease into anal canal (clinical important for planning sphincter preserving surgery)

Figure. Endorectal ultrasound of a T3 tumor of the rectum, extension through the muscularis propria, and into perirectal fat.

Magnetic Resonance Imaging (MRI)

• Greater accuracy for T3 or T4 stage of tumor, more accurate for N staging than EUS

• Also helpful in lateral extension of disease, critical in predicting circumferential resection margin for surgical excision.

• Predict tumor regression grade• LN accuracy similar to CT (<80%)• MRI predicted TRG after NACT and CRM are significant

prognostic markers.• Mercury study:

– Specificity for predicting clear margins was 92%

Endorectal coil MRI• Larger field of view.• Better visualization of

mesorectum• Identification of

perirectal nodes( 95% accuracy)

• Identification of sphincter inv.( 100%)

Figure: Mucinous adenocarcinoma of the rectum. T2-weighted MRI shows high signal intensity (arrowheads) of the cancer lesion in right anterolateral side of the rectal wall.

Figure: Normal rectal and perirectal anatomy on high-resolution T2-weighted MRI. Rectal mucosa (M), submucosa (SM), and muscularis propria (PM) are well discriminated. Mesorectal fascia appears as a thin, low-signal-intensity structure (arrowheads) and fuses with the remnant of urogenital septum making Denonvilliers fascia (arrows).

CT scan

• Part of routine workup of patients( baseline CECT chest and abdomen with pelvis)

• Useful in identifying enlarged pelvic lymph-nodes and metastasis outside the pelvis than the extent or stage of primary tumor

• Limited utility in small primary cancer• Overall Sensitivity 70-85%• Specificity 30-80%

Figure: Mucinous adenocarcinoma of the rectum. CT scan shows a large heterogeneous mass (M) with areas of cystic components. Note marked luminal narrowing of the rectum (arrow).

Figure:   Rectal cancer with uterine invasion. CT scan shows a large heterogeneous rectal mass (M) with compression and direct invasion into the posterior wall of the uterus (U).

PET with FDG

• Routinely not recommended• Shows promise as the most sensitive study for

the detection of METASTATIC disease in the LIVER and abdominal LN.

• Sensitivity of 97% and specificity of 76% in evaluating for recurrent colorectal cancer.

• to restage patients following preoperative chemoradiation.

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