Gastro - Colorectal Cancer Flashcards
Definition of colorectal Cancer
Epidemiology of Colorectal Ca
Malignant cells present in the colon. It is the most common type of cancer of the GIT
3rd most common and 2nd in cancer deaths worldwide
What organs are found in the intraperitoneal space? What organs are found in the retroperitoneal space?
Intraperitoneal
First part of duodenum
Small intestines (duodenum, jejunum, ileum)
Transverse colon
Sigmoid colon
Rectum
Retroperitoneal
Kidneys
Ureter
Adrenal gland
Abdominal aorta
Inferior vena cava
Distal duodenum
Ascending colon
Descending colon
Anal canal
Layer of the GIT
Mucosa – surrounds lumen of GIT and comes into direct contact with food. Lined with intestinal glands (colonic crypts) that are specialised in absorption
Submucosa – dense layer of tissue that contains blood vessels, lymphatics and nerves.
Muscularis – contracts to move food though bowl
Serosa
OR
Adventitia
Serosa is if it is intraperitoneal and adventitia for retroperitoneal parts of GIT
What is the most common type of colorectal cancer?
Adenocarcinoma which means they occur from the cells lining the intestinal glands.
Adenocarcinomas are the malignant evolution of polyps which occur when cells divide faster than usual
Causes of Colorectal cancers
Sporadic mutation
Known Mutations:
APC gene mutation.
K- RAS gene
p53
Mutations in DNA repair genes
Which types of polyps are considered premalignous? How do they appear under microscope?
Adenomatous and serrated
Adenomatous occur due to APC mutation and cells look normal
Serrated have mutations in DNA repair genes and have saw-tooth appearance
Colorectal cancer staging?
Stage 0 – carcinoma in situ (not passed mucosa)
Stage 1 – beyond mucosa no lymph node invasion
Stage 2 – entire wall and may reach nearby organs, no lymph node invasion
Stage 3 – reached lymph nodes but not distant organs
Stage 4 – metastatic, reached distant organs
What organs are affected by metastasis of colorectal cancer?
If cancer is in colon it often metastases to liver
If cancer is in rectum it often metastasises to lungs. This is because the rectal venus plexus can bypass the portal system
Risk factors of Colorectal Cancer?
Modifiable
Smoking
Red meat\ processed food
Lack of fibre
Obesity
Sedentary lifestyle
Alcohol
Non-modifiable
Elderly (90% dx over 50 but increase in young people)
Male
Inflammatory bowel disease
Adenomatous polyps (which progress to cancer, inflammatory and hyperplastic don’t have risk of malignancy)
Colorectal cancer is associated with:
Familial adenomatous polyposis.
Hereditary nonpolyposis
Sx of Colorectal cancer based on location?
Ascending colon
Pain and weight loss due to growth beyond mucosa
Large growth and late diagnosis as no bowel obstruction
Can ulcerate and bleed causing anemia.
Descending colon
Ring shaped infiltrating mass
Napkin ring constriction
Haematochezia
Colic pain
Dx of colorectal cancer?
Colonoscopy w biopsy - gold standard; look up until cecum
Fecal occult blood testing – for GI bleed (done every 2 hrs from 60y/o in UK)
Check for CEA tumour marker elevation (nonspecific), CA 19-9 can also be looked at
Barium enema – apple core sign (shows restriction of lumen most often in descending colon)
How can colorectal cancers be detected early? Who would be the target group for early detection?
Routine colonoscopy and fecal occult blood testing
Pt with relatives with colorectal cancer
Pt with IBD
Pt with familial adenomatous polyposis or hereditary nonpolyposis
Tx of colorectal cancer?
DEPENDS ON STAGE OF Ca
Early – surgical resection of tumour confided to wall of tumour or colectomy. Chemotherapy to treat nearby lymph nodes
Metastatic – no cure, chemo (5 fluorouracil), and surgery to ease symptoms (palliative)
At what age is screening of colorectal cancer done?
45 y\o
Or if pt has family hx of colorectal cancer then it is done 10 yrs before the diagnosis age of relative
What diseases are associated with a higher risk of colon cancer?
IBD
Familial adenomatous polyposis
Hereditary nonpolyposis colorectal cancer
