Rectum 12 to 15 cm in length from the rectosigmoid junction to
the puborectalis ring upper third middle third (posterior border of
the rectouterine pouch or rectovesical space) lowest third no
serosal barrier
Slide 5
Colonic nodal drainage consists of pericolic nodes and nodes in
association with the vascular supply to the colon (i.e., mesenteric
nodes rectal nodal drainage include the perirectal, presacral, and
internal iliac nodes.
Slide 6
Epidemiology, Molecular Cascade, Risk Factors, Hereditary
Disease, and Clinical Presentation The median age is in the seventh
decade chemical carcinogens Environmental and dietary factors
Slide 7
Factors shown to increase the risk include increasing age, male
sex,rectal cancer excessive alcohol use family history of
colorectal cancer, increasing height, increasing body mass index,
processed meat intake low folate consumption. consumption of fruits
and vegetables ? The role of chemopreventive agents (carotenoids,
aspirin, and other nonsteroidal anti-inflammatory drugs) ?
Slide 8
Slide 9
Biologic and genetic pathways of development of colorectal
cancer proto-oncogenes (mutations in the ras proto- oncogene.)
tumor suppressor genes (inactivation adenomatous polyposis coli
(APC) and P53)
Slide 10
: microsatellite instability Biology The majority of HNPCCas
well as a minority of sporadic colorectal cancers harbor
microsatellite instability. mutations in genes encoding enzymes
that repair DNA replication errors Studies have suggested that
patients with tumors possessing a high frequency of microsatellite
instability have a more favorable outcome and develop fewer
metastases
Slide 11
Colorectal cancer minimal or no symptoms Nonspecific bowel
habits, weakness, intermittent abdominal pain, nausea, and
vomiting. The persistence of such symptoms as well as any evidence
of iron deficiency anemia should be investigated
Slide 12
Clinical Presentation right colon exophytic,iron deficiency
anemia left colon and sigmoid colon deeply invasive, annular, and
accompanied by obstruction and rectal bleeding Rectal cancer
frequently results in bleeding and alterations in bowel
habits.
Slide 13
FIGURE 58.1. Idealized depiction of peritoneal relationships in
the colon and rectum. The transverse and sigmoid colon are
intraperitoneal, with a complete peritoneal covering (serosa) and
mesentery. The ascending and descending colon are retroperitoneal,
lack a true mesentery, and usually do not have a peritoneal
covering posteriorly or laterally. The upper rectum begins above
the peritoneal reflection and has peritoneum anteriorly and
laterally. The lower half to two thirds of the rectum is below the
peritoneal reflection (infraperitoneal).
Slide 14
Slide 15
Slide 16
Prevention and Early Detection Neoplastic polyps are precursors
of colon cancers Most colorectal cancers arise from pre-existing
polyps Patients with neoplastic polyps should be considered at high
risk for large bowel cancer, and polypectomy may reduce this risk.
With the availability of the flexible colonoscope and endoscopic
polypectomy, polyps can be removed at a premalignant stage and
patients followed closely.
Slide 17
The goal of screening is to detect preinvasive polyps or early
invasive cancer. The presence of polyps increases the risk for
cancer to approximately 15%. Data from programs in which
proctoscopy is performed annually suggest that routinely scheduled
polypectomy reduces the development of subsequent bowel cancer by
80% or more.
Slide 18
The American Cancer Society has recommended screening should
begin at age 50 in the average risk patient by either: Annual fecal
occult blood test and/or flexible sigmoidoscopy every 5 years,
Double contrast barium enema every 5 years Colonoscopy every 10
years
Slide 19
patients at high risk adenomatous polyps history of colorectal
cancer first-degree relative with colorectal cancer or adenomas
inflammatory bowel disease family history or genetic testing
Slide 20
Intensive surveillance is recommended for patients at high risk
1. Computed tomography (CT) colonography 2. genetic fecal testing
are being studied Although screening methods can detect colorectal
cancer at an early stage,
Pathology (>90%) adenocarcinomas Scc, carcinoid,
leiomyosarcoma, and lymphoma. Most grading systems classify
adenocarcinoma as well, either moderately or poorly
differentiated.
Slide 22
Pathways of Spread invade from mucosa through the bowel wall
and beyond, with involvement of lymphatic channels and lymph nodes.
Hematogenous spread can occur, primarily to the lung and liver.
There is little propensity for colon cancer to spread
longitudinally within the bowel wall, in contrast to esophageal or
gastric cancers
Slide 23
Patient Evaluation/Staging Pretreatment evaluation 1.
pathological confirmation 2. colonoscopy ( synchronous primaries
occurring in 3% to 5%) 3. CBC with LFT and CEA 4. abdominal and
pelvic CT scan 5. CXR 6. (PET) scan 7. (MRI), 8. Ultrasound
Slide 24
(PET) scan .
Slide 25
Prognostic factors depth of tumor invasion into and beyond the
bowel wall the number of involved regional lymph nodes presence or
absence of distant metastases The tumor, node, metastasis (TNM)
system of the American Joint Committee on Cancer can be used as a
clinical (preoperative) or postoperative staging system
Slide 26
Colorectal Tumor, Node, Metastasis Staging, 2002 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 the subserosa, or into
non-peritonealized pericolic or perirectal tissues T4 Tumor
directly invades other organs or structuresa and/or perforates
visceral peritoneum (includes invasion of other segments of
colon)
Slide 27
Direct invasion in T4 includes invasion of other segments of
the colorectum by way of the serosa; for example, invasion of the
sigmoid by a carcinoma of the cecum. Tumor that is adherent to
other organs or structures, macroscopically, is classified as T4.
However, if no tumor is present in the adhesion, microscopically,
the classification should be pT3
Slide 28
N1 Metastasis in one to three regional lymph nodes N2
Metastasis in four or more regional lymph nodes (Tumor nodules in
the pericolonic adipose tissue without evidence of residual lymph
node are classified as a regional lymph node metastases)
Slide 29
Therapy of Colon Cancer Surgery based on the anatomy and
mechanisms by which this disease spreads. avoid cutting across
tumor in intramural lymphatics, sufficient lengths of bowel must be
resected
Slide 30
Resection results in excellent cure rates average 5-year
survival o 97% for T1N0 o 85% to 90% for T2N0 o 65% to 75% for
T3T4N0 o 50% (T3N+) and 35% (T4N+)
Slide 31
American Joint Committee on Cancer Stage Grouping MACDukes MNT
Stage AAT1I B1AT2 B2BT3IIA B3BT4IIB
Adjuvant Chemotherapy addition of 5FU (5-fluorouacil) and
leucovorin improves survival for resected stage III patients
Capecitabine, an oral 5-FU prodrug, has demonstrated similar
overall and disease free survival rates to 5- FU/leucovorin in
patients with resected stage III colon cancer
5-FU/leucororin/oxaliplatin in resected stage II or III colon
cancer patients showed improved disease-free FU/LV/oxaliplatin as
the new standard chemotherapeutic regimen in the adjuvant treatment
of completely resected, high-risk colon cancer The efficacy of
agents such as bevacizumab and cetuximab as adjuvant therapy is
being investigated
Slide 34
Adjuvant Irradiation with or without Concurrent Chemotherapy
The potential indications for adjuvant radiation therapy in colon
cancer are based on analyses of patterns of failure following
resection local failure in colon cancer also depends on anatomic
origin 1. ascending and descending colon 2. mid-sigmoid and
mid-transverse colon 3. cecal, hepatic/splenic flexure, and
proximal/distal sigmoid tumors are variable depending on the amount
of mesentery present, tumor extension, and the adequacy of radial
margins. When colon cancers adhere to or invade adjacent
structures, local failure rates exceed 30% following surgery
alone.
Slide 35
In summary, local failure occurs in patients with colonic
tumors where there are anatomic constraints on radial resection
margins, including tumors adherent to or invading adjacent
structures.
Slide 36
To summarize, these studies have suggested that operative bed
failures in high-risk patients undergoing resection alone are at
least 30%, and that the risk of local failure is reduced by the
administration of adjuvant radiation therapy. Irradiated patients
included those with T4N0/N+, T3N+ disease (excluding mid-sigmoid
and mid- transverse colon) and T3N0 patients with margins of 1 cm
IORT Ten to 12.5 Gy for complete resection 12.5 to 15 Gy for
microscopic residual ">
IORT No IORT metastases less than T4 disease adequate margins
>1 cm IORT Ten to 12.5 Gy for complete resection 12.5 to 15 Gy
for microscopic residual 17.5 to 20 Gy for gross residual disease.
The risk of peripheral neuropathy was 20% for doses >15 Gy. IORT
improves local control, especially with a gross total resection,
but not survival for locally advanced rectal cancer.
Slide 106
Reirradiation Recurrent rectal cancer is often approached the
same way as T4 disease with an aggressive treatment plan of CHRTby
surgery and then adjuvant CHT. IORT is considered The 5-year
overall survival is approximately 20%.The local control is about
40% in patients with no prior radiation to 10% to 20% in patients
who had prior radiation.