Colorectal cancer Flashcards
Define colorectal cancer
Cancer involving the large intestine (colon and rectum)
Where does the colon begin?
Ileo-caecal junction
What are the 5 parts of the colon?
Caecum Ascending colon Transverse colon Descending colon Sigmoid colon
What is the function of the colon?
Receives digested food
Absorbs water and electrolytes
Forms faeces
What vessel supplies midgut-derived structures?
SMA
What vessel supplies hindgut-derived structures?
IMA
What is the blood supply of the ascending colon?
SMA
- ileocolic aa
- right colic aa
What are the branches of the ileocolic artery?
Colic aa
Anterior caecal aa
Posterior caecal aa
What is the blood supply of the transverse colon?
SMA
- middle colic aa
What is the blood supply of the descending colon?
IMA
- left colic aa
What is the blood supply of the sigmoid colon?
IMA
- sigmoid arteries
What is the Marginal Artery of Drummond?
Anastomoses between SMA and IMA that provides collateral supply to the colon
What is the lymphatic drainage of the colon?
SMN and IMN -> cisterna chyli -> thoracic duct
What are the 2 major flexures of the rectum?
Sacral
Anorectal
Give the blood supply of the rectum
IMA - superior rectal Internal iliac - middle rectal Internal pudendal - inferior rectal
Discuss the epidemiology of colorectal cancer
> 65yo
W>B
M>F
Name risk factors for colorectal cancer
>65yo Smoking Obesity Diet (red meat, processed, alcohol) IBD Personal history of polyps of cancer
Name screening modalities for colorectal cancer
Faecal occult blood test
Sigmoidoscopy
Colonoscopy
What is the pathogenesis of colorectal cancer?
Sporadic
Inherited
What are the 3 genetic pathways implicated in the pathogenesis of colorectal cancer?
- Chromosomal instability
- Microsomal instability
- Serrated pathway
Explain the chromosomal instability pathway
Inactivating tumour suppressor genes (APC)
Activating proto-oncogenes (KRAS)
Explain the microsomal instability pathway
Inactivation of MMR genes (MLH1) due to epigenetic silencing via promoter hypermethylation
Explain the serrated pathway
Proto-oncogene BRAF mutation
How is colorectal cancer staged?
AJCC TNM staging
Modified Duke’s = old system
Discuss the AJCC TNM staging of colorectal cancer
T1 - invades submucosa
T2 - invades muscularis propria
T3 - invades subserosa or non-peritonealized pericolic/perirectal tissue
T4 - directly invades other structures or visceral peritoneum
N1 = 1-3 LN N2 = >3 LN
Name suspicious symptoms that clinically suggest colorectal cancer
Significant weight loss Constipation Change in bowel habits PR bleeding Rectal mass Tenesmus Rectal pain
How can complications of colorectal cancer present clinically?
Intestinal obstruction Perforation Peritonitis Abdominal pain Iron deficiency anemia Acute GI bleed
How can colorectal cancer spread?
Lymphatic
Hematogenous
Contiguous
Transperitoneal
Name the most common sites of colorectal cancer metastases
LN
Liver
Lungs
Peritoneum
Where can tumours in the distal rectum metastasize to initially and why?
Lungs
Inferior rectal vv drains into IVC
Name atypical symptoms of colorectal cancer
Pneumaturia
Fever of unknown origin
Name investigations in colorectal cancer
Bloods - FBC, U+E, LFT, CEA, HIV Imaging - CXR - AXR Colonoscopy Staging CT
Name treatment options for colorectal cancer
Chemotherapy
Radiotherapy
Surgical
Name indications for adjuvant chemotherapy in colorectal cancer
Metastatic
T3, T4 tumours
Positive lymph nodes
High risk features
Discuss palliation in colorectal cancer
Analgesia Bowel obstruction surgery ERCP (obstructive jaundice) Psychologist Radiotherapy Chemotherapy
How long is surveillance in colorectal cancer carried out for?
Minimum 5 years
How do you perform surveillance in post-colorectal cancer patients?
Clinical
Bloods
CT scan
Colonoscopy
