Colorectal cancer and screening Flashcards
What cell type are most colorectal cancers?
adenocarcinoma - 95%
What are some risk factors for sporadic CRC?
age, male, smoking, alcohol, diabetes, obesity, low fibre diet, low exercise, adenoma/previous CRC
What are some other risk factors for CRC?
IBD and familial risk eg FAP, HNPCC
What do the majority of CRC arise from?
pre-existing polyps
What are adenomas and name the 3 subtypes
high risk lesions which are benign, pre-malignant tumours of the glandular tissue
tubular, villous, tubulovillous
What are the 3 key moments of an adenoma progressing to a carcinoma? Give some examples
activation of oncogenes - k-ras
loss of tumour suppressor genes - p53
defective DNA repair pathway - microsatellite instability
How can CRC present?
rectal bleeding, change in bowel habit, weight loss, anaemia, palpable mass
When would you investigate 1 symptom of CRC and when would you investigate >1 symptom of CRC?
> 60 years old
>40 years old
What is the main investigation for CRC - what does it allow and what are the risks?
colonoscopy - allow biopsies and polypectomy
sedation, bowel preparation, perforation and bleeding
What are some radiological imaging techniques used in CRC and what are the disadvantages?
CT abdomen/pelvis, CT colonography and barium enema
ionising radiation, bowel preparation and no biopsies or therapy possible
What scans are used to help stage cancer?
CT, PET, MRI, rectal endoscopic ultrasound
What are the 2 staging classifications for CRC and briefly describe the stages
TNM - T1-4, N0-1, M0-1
Dukes - A,B,C,D, A = mucosa, B = muscle layer
What are the things to consider in surgeries carried out in CRC?
lymph node removal, stoma?, laparotomy vs laparoscopy, endoscopic or local polyp resection and partial hepatectomy for metastases
How is chemotherapy used in CRC?
adjuvant = after surgery
mop up micro metastases
Dukes B/C with positive LN histology
palliative
How is radiotherapy used in CRC?
Rectal cancer ONLY
neoadjuvant = before surgery to control the primary tumour
Apart from chemotherapy what is the other palliative option for CRC?
colonic stenting
What is the aim of population CRC screening?
detect premalignant adenomas/early carcinomas
What are some methods of population CRC screening?
FOBT, FIT, colonoscopy, flexible sigmoidoscopy, CT colonography
Describe the Scottish bowel screening
introduced in 2007 using FOBT to 50-74 year olds every 2 years
If positive are called for a colonoscopy
reduced mortality by 15% and made a large shift to more dukes A being diagnosed
What are some risk factors classing you as high risk for CRC?
previous adenoma/CRC
Heritable conditions eg FAP/HNPPC
IBD
familial risk - other family members
What is FAP?
autosomal dominant condition of the mutation of the APC gene on chromosome 5 leading to >100 polyps in the colon leading to high risk of developing CRC early in life
How are patients with FAP treated in respect to CRC risk?
annual colonoscopy
prophylactic polypectomy
What are some extra-colonic manifestations of CRC?
retinal hypertrophy and duodenal adenomas so must be given upper GI surveillance aswell
What is HNPCC?
autosomal dominant condition with early onset right hand side CRC with associated risk of endometrial, stomach and pancreatic cancer
How is HNPCC treated in respect to CRC risk?
Genetic testing
2 yearly colonoscopy
How are other high risk groups surveillance for CRC?
IBD - surveillance colonoscopy 10 years after diagnosed
Familial history - depends on number of relatives
previous CRC - 5 yearly colonoscopy
previous adenoma - depend on size, number, degree of dysplasia
