Colorectal Cancer Flashcards
Staging colorectal cancer?
TNM
Tumour
Tis
T1: invade submucosa
T2: invade muscularis
T3: through propria into subserosa or nonperitonealized pericolic or perirectal tissues
T4: directly invade other organs or structures or perforate visceral peritoneum
Nodes
N1 : metastasis in 1-3 pericolic or perirectal lymph nodes
N2: ≥ 4
Distant Metastasis
M1
Symptoms and Presentation colorectal cancer? (5)
• Suspicious symtoms/signs: weight loss, constipation, change bowel habits, Pr bleed, rectal mass, tenesmus and rectal pain
• asymptomatic discovered by routine screening
• emergency admission with complications: intestinal obstruction,obstructive symptoms (colicky pain), perforation and peritonitis, rarely acute gi bleed, abdo pain, unexplained iron deficiency anemia
• symptoms metastasis: RUQ pain, abdominal distention, early satiety, supraclavicular adenopathy, periumbilical nodules.
• unusual presentations:malignant fistula (especially caecal, sigmoid carcinoma), fever unknown origin, abscesses (intra-abdominal, retroperitoneal, abdominal wall, intrahepatic - due to localized perforated colon cancer), liver mets found incidentally
Treatment T1/T2 Mo rectal cancer?
Surgery with adjuvant chemo
Treatment T3/T4 Mo rectal cancer? (3)
• Neoadjuvant chemosensitising radiotherapy
• Surgery: lar (low anterior resection) or Apr (abdominal perineal resection)
• adjuvant chemo
Treatment Mo colon cancer?
• Surgical resection eg right hemicolectomy if resectable
• adjuvant chemo
Risk factors colorectal cancer? (9)
• Older age > 65
• smoking
• obesity
• diet: red and processed meat,
. alcohol heavy use
• IBD
• personal, family history
• colorectal polyps (premalignant)
• hereditary coloretal carcinoma syndrome eg lynch syndrome ( hereditary non-polyposis colorectal cancer hnpcc ), fap
Pathogenesis hereditary Colorectal cancer? (3)
• Chromosomal instability (CIN) pathway
• microsomal instability (msi)
• serrated pathway
Briefly explain CIN pathway in the pathogenesis of colorectal cancer (3)
Chromosomal instability. Conventional adenoma -carcinoma sequence 70%
• Inactivate mutations tumour suppressor genes eg APC (adenomatous polyposis coli) gene! → early adenoma
• activate mutations in proto-oncogenes eg KRAS! → increased clonal expansion cells → late Adenoma
• subsequent loss heterozygosity for chromosome 18q and loss tumour suppressor p53! confer these expanding cells without additional growth advantages → invasive cancer.
Briefly explain MSI pathway in the pathogenesis of colorectal cancer
Mismatch repair deficiency. Microsatellite instability pathway 3-5%
•Loss APC gene and inactivation mismatch repair (mmr)! genes eg MutL homolog 1 (MLH1) due to epigenetic silencing via promoter hyper methylation → adenoma
• mutations proliferative and differentiation target genes eg tgfbrii (transforming growth factor ß receptor 2); proteins involved in apoptosis regulation eg BAX → microsatellite unstable invasive cancer
Briefly explain serrated pathway in the pathogenesis of colorectal cancer (2)
Serrated polyp path 20- 30%
• Hypermethylation genes → Proto-oncogene BRAF mutation! → increased mapks/ ERKs signalling → cell proliferation →serrated adenoma
• methylation other genes and loss tumour suppressor genes eg tp53, p16 → cancer
How can colorectal cancer be screened for?
Faecal occult blood test from age 55. If positive → colonoscopy
(Not done in SA)
Most common metastatic sites of colorectal cancer? (4)
• Regional lymph nodes
• liver next (haematogenous dissemination via portal vein) (ruq pain, distention, early satiety)
• then lungs (distal rectum first to lungs. Inferior rectal vein drain into IVC, not portal)
• bone, peritoneum, brain
Most common type colorectal cancer?
Adenocarcinoma
Bloods Investigations for colorectal cancer? (5)
• FBC (if anemia, Pr bleed),
• UCE (bowel obstruction - electrolyte imbalance;need normal UCE for CT contrast for staging )
• LFT (need normal for chemo)
• CEA: tumour marker for monitoring during treatment and surveillance.
• HIV: cancer is an AIDS defining condition.
Imaging Investigations for colorectal cancer? (5)
• CXR: rule out cannon ball lung metastasis
• AXR: rule out bowel obstruction because will need bowel prep for colonoscopy.
• colonoscopy: id tumour site, biopsy, remove other premalignant lesions eg polyps, id impending or partial bowel obstruction that doesn’t allow scope progression, palliation impending bowel obstruction using colonic stent.
( • double contrast barium enema dcbe: was used to show apple core lesion suggestive of CRC but not done anymore, lots of complications , ct preferred )
• CT chest abdomen pelvis: staging for metastasis
• MRI: local t and N staging rectal cancers, not colon.
