Download COLORECTAL CANCER

COLORECTAL CANCER
‫ الدكتور خلدون ذنون‬:‫المحاضر‬
‫ المرحله الرابعة‬-‫كلية طب نينوى‬
Objectives
1. To know the features of such serious disease for the sake of early
diagnosis.
2. endoscopy and biopsy are essential.
3. Staging of the disease which influence management.
4. Surgery, chemotherapy, and radiotherapy are the mainstay of
management.
Introduction
•
Its incidence is increasing in Iraq .
•
The second most common malignancy & the second leading
cause of cancer death in the west .
•
Occur mainly after 50 y of age .
Etiology
Risk factors : 80% sporadic , 10-15% family history , 5% hereditary
non-polyposis colon cancer , 1% familial adenomatous polyposis ,
1% inflammatory bowel disease .
1
A-Environmental factors : account for 80% of sporadic colorectal CA
1.Dietary factors : red meat (carcinogenic amines formed during
cooking) , saturated animal fat (high faecal bile acids) , risk is decreased
by : dietary fiber , fruit & vegetables , calcium which binds & precipitates
bile acids , folic acid .
2.Non-dietary risk factors : colorectal adenoma , long standing
extensive UC , acromegaly , pelvic radiotherapy , obesity & sedentary life
style , alcohol & tobacco (weak association), cholecystectomy, type 11
diabetes.
B-Genetic factors
•
Due to chromosomal instability and multiple genetic mutations .
•
10% strong family history of CA colon at an early age .
•
1% familial adenomatous polyposis – autosomal dominant .
•
5% hereditary non-polyposis colon cancer :
. Autosomal dominant
. Failure of DNA mismatch repair leads to multiple
somatic
mutations throughout the genome.
. Life time risk of colon cancer is 80%
. Mean age of disease onset is 45y
. 2/3 tumor occurs in the proximal colon (sporadic
cancer-distal)
2
. Increase incidence of cancer in endometrium , urinary
tract ,
stomach & pancreas
. Genetic testing & colonoscopy every 1-2 years for such
families
begin at age 25 year
Pathology
•
Most tumors arise from benign adenomatous polyp .
•
More than 65% occur in rectosigmoid , 15% in caecum &
ascending colon .
•
Polypoid (fungating) or annular & constricting .
•
Spread through bowel wall , rectal cancer may invade pelvic
viscera.
•
Lymphatic invasion is common & through portal and systemic
circulation reach the liver and less commonly , the lungs .
•
Tumor stage at diagnosis determines the prognosis .
Dukes stage
A- Tumor limited to mucosa & submucosa
(highest
survival) .
B- Cancer involves muscularis &
extends into or through
3
serosa .
C- Regional lymph node involvement
D- Distant metastasis e.g liver , lung
(lowest survival) .
Clinical features
•
Symptoms depend on tumor location .
•
Left colon cancer : fresh rectal bleeding is common & obstruction
occur early.
•
Right colon cancer : present with anaemia from occult bleeding ,
altered bowel habit , obstruction is late , 2/3 colicky lower
abdominal pain, rectal bleeding in 50% , minority develop
obstruction or perforation leading to peritonitis , localised abscess
or fistula formation .
•
Rectal cancer : early bleeding , mucus discharge , feeling of
incomplete emptying .
•
10-20% of all patients present with iron deficiency anaemia or
weight loss .
•
sometimes it presents as fever of unknown origin .
•
Examination : palpable mass , anaemia , hepatomegaly , low
rectal tumors are palpable by PR .
4
Investigations
 Colonoscopy is the investigation of choice as it is more sensitive
& more specific than barium enema , biopsies can be taken &
polyp removed.
 CT detects abdominal involvement of the viscera e.g liver , and
lymph node involvement i.e stage of tumor , intraoperative U/S
can do the same job .
 Endoanal U/S or pelvic MRI stages rectal cancer .
 CT colography is sensitive non-invasive technique for diagnosis.
 Increased CEA : non-specific , of little use in the diagnosis but
valuable in follow up after surgical resection to detect recurrence .
Management
A- surgery : removal of the cancer with adequate resection of margins
and pericolic lymph nodes , some may need colostomy others need end to
end anastomosis .
•
CA near anal verge may need abdomino-perineal resection with
colostomy .
• solitary hepatic or lung metastasis may be resected .
•
Post-operative colonoscopy after 6-12 months & periodically
there after to detect recurrence or new cancer which occurs in 6% .
B- Adjuvant therapy
5
•
2/3 have lymph node or distant spread at presentation & so
surgery is not curative .
•
5-fluorouracil + folinic acid (reduce toxicity) improves survival in
patient with Dukes C stage after surgery and is also palliative for
patients with metastasis .
•
Pre-operative radiotherapy is given to patients with large-fixed
rectal cancers to down-stage the tumor.
• Pelvic radiation for pain and bleeding.
•
Post-operative radiotherapy to patients with Dukes C & some
Dukes B rectal cancers to reduce the risk of recurrence .
• Monoclonal antibodies (bevacizumab) alone or with chemotherapy
are useful for metastatic disease.
• Tumor obstruction can be relieved by endoscopic laser ablation or
metal stent.
Secondary prevention & screening
• Detect & remove lesions at an early or pre-malignant stage .
•
Wide spread screening by regular faecal occult blood FOB
testing , reduces colorectal cancer mortality by 15-20% & detect
cancer early , but it lacks sensitivity&specificity , USA: annual
FOB screen after 50y.
•
Colonoscopy
is
the
gold
6
standard(needs
well-trained
persons,expensive,risk of the procedure).
• Flexible sigmoidoscopy is the alternative option, it reduces overall
colorectal cancer mortality by 35% & 70% for rectosigmoid CA. ,
done in USA every 5 years for those above 50 years of age .
•
Screening for high-risk patients by molecular genetic analysis :
not yet available .
7