RECTAL CANCER Flashcards
ANATOMY
Begins at the rectosigmoid junction, at level of third sacral vertebra
o Ends at the anorectal junction, 2-3 cm in front of and a little below the coccyx
Divided into 3 parts:
Upper third, Middle third, Lower third
3 distinct intraluminal curves
(Valves of Houston)
Peritoneal Relations
Superior 1/3rd of the rectum: Covered by peritoneum on the
anterior and lateral surfaces
§ 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
NOTE: Distal rectal tumors have no serosal barrier to invasion of adjacent structures and are more difficult to resect given the close confines of
the deep pelvis.
BLOOD SUPPLY
Arterial supply
¨ Superior rectal A – fr. IMA; supplies upper and middle rectum
¨ Middle rectal A- fr. Internal iliac A. (supplies lower rectum)
¨ Inferior rectal A- fr. Internal pudendal A.
§ Venous drainage
¨ Superior rectal V- upper & middle third rectum
¨ Middle rectal V- lower rectum and upper anal canal
¨ Inferior rectal vein- lower anal canal
§ Innervations
¨ Sympathetic: L1-L3, Hypogastric nerve
¨ ParaSympathetic: S2-S4
§ 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 is the third most frequently diagnosed cancer in the US men and women.
o It represents 38% of colorectal cancers
o Median age- 7th decade but can occur any time in adulthood. Same incidence male vs. female
TNM
TX Primary tumor cannot be assessed
T0 No evidence of primary tumor
Tis Carcinoma in situ: intraepithelial or invasion of lamina propria
T1 Tumor invades submucosa
T2 Tumor invades muscularis propria
T3 Tumor invades through the muscularis propria into pericolorectal tissues
T4a Tumor penetrates to the surface of the visceral peritoneum
T4b Tumor directly invades or is adherent to other organs or structures
DUKES CLASSIFICATION
Dukes A: Invasion into but not through
the bowel wall.
§ Dukes B: Invasion through the bowel
wall but not involving lymph nodes.
§ Dukes C: Involvement of lymph nodes
§ Dukes D: Widespread metastases
o Modified astler coller classification-
Stage B1: Extending into muscularis
propria but not penetrating through it;
nodes not involved.
§ Stage B2: Penetrating through
muscularis propria; nodes not involved
§ Stage C1: Extending into muscularis
propria but not penetrating through it.
Nodes involved
§ Stage C2: Penetrating through
muscularis propria. Nodes involved
§ Stage D: Distant metastatic spread
RISK FACTORS
Etiological agents
§ Environmental & dietary factors
§ Chemical carcinogenesis.
o Associated risk factors
§ Male sex
§ Family history of colorectal cancer
§ Personal history of colorectal cancer, ovary, endometrial, breast
§ Excessive BMI
§ Processed meat intake
§ Excessive alcohol intake
§ Low folate consumption
§ Neoplastic polyps
o Hereditary Conditions (FAP, HNPCC)
PROGNOSTIC FACTORS
Good prognostic factors
§ Old age
§ Gender(F>M)
§ Asymptomatic pts
§ Polypoidal lesions
§ Diploid
o Poor prognostic factors
§ Obstruction
§ Perforation
§ Ulcerative lesion
§ Adjacent structures involvement
§ Positive margins
§ LVSI
§ Signet cell carcinoma
§ High CEA
§ Tethered and fixed cancer
CLINICS
Symptoms
§ Asymptomatic
§ Change in bowel habit (diarrhoea, constipation, narrow stool, incomplete evacuation, tenesmus).
§ Blood PR.
§ Abdominal discomfort (pain, fullness, cramps, bloating, vomiting).
§ Weight loss, tiredness.
o Acute Presentations
§ Intestinal obstruction
§ Perforation
§ Massive bleeding
o Signs
§ Pallor
§ Abdominal mass
§ PR mass
§ Jaundice
§ Nodular liver
§ Ascites
o Rectal metastasis travel along portal drainage to liver via superior rectal vein as well as systemic drainage to lung via middle inferior rectal veins.
DIAGNOSIS
History—including family history of colorectal cancer or polyps
o Physical examinations including
§ DRE
§ Complete pelvic examination in women: size, location, ulceration, mobile vs. tethered vs. fixed, distance from anal verge and sphincter
functions.
o Laboratory exams
§ CEA: High CEA levels associated with poorer survival
§ Routine investigation: Complete blood count, KFT, LFT + Chest X-ray
o Proctoscopy—including assessment of mobility, minimum diameter of the lumen, and distance from the anal verge
o Biopsy of the primary tumor
o Transrectal ultrasound –EUS
§ use for clinical staging.
§ 80-95% accurate in tumor staging
§ 70-75% accurate in mesorectal lymph node staging
§ Very good at demonstrating layers of rectal wall
§ 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)
o CT scan
§ Part of routine workup of patients
§ 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
§ Sensitivity 50-80%
§ Specificity 30-80%
§ Ability to detect pelvic and para-aortic lymph nodes is higher than peri-rectal lymph nodes.
§
o Magnetic Resonance Imaging (MRI)
§ Greater accuracy in defining extent of rectal cancer extension and also location & stage of tumor
§ Also helpful in lateral extension of disease, critical in predicting circumferential margin for surgical excision.
§ Different approaches (body coils, endorectal MRI & phased array technique)
§
o PET with FDG
§ Shows promise as the most sensitive study for the detection of metastatic disease in the liver and elsewhere.
§ Sensitivity of 97% and specificity of 76% in evaluating for recurrent colorectal cancer
SURGERY
(distal 15 cm of the large intestine). Choice of operation depends on individual case; types of operations:
§ Low anterior resection of rectum (LAR): curative procedure of choice if adequate distal margins; uses technique of total mesorectal
excision.
Tumours located in the distal 3-5 cm of the rectum present the greatest challenge to the surgeon:
¨ Abdominoperineal resection of rectum (APR): if adequate distal margins cannot be obtained; involves the removal of distal
sigmoid colon, rectum, and anus – permanent end colostomy required
¨ Local excision: for select T1 lesions only. Above T2à resection is mendatory.
Palliative procedures involve proximal diversion with an ostomy for obstruction and radiation for bleeding or pain.
ADJUVANT THERAPY
Combined neoadjuvant chemoradiation therapy followed by post-operative adjuvant chemotherapy for stages II and III
The retroperitoneal pelvic location being a limitation for surgeons provide an opportunity for treatment by radiation therapy that is
not feasible for colon tumors
§ Pre-operative radiation (usually 4500 to 5040 cGy) with infusional 5-FU–leucovorin, 5-FU alone, or capecitabineà dramatic
downstaging
¨ Can help the surgeon to achieve clear margins without compromising the ANS.
¨ can even result in the disappearance of the tumor, but difficult to predict which patients will benefit from it
The goal is to downgrade the tumor in order to be able to preform LAR and preserve continency
