Oncology
Colorectal Cancer
대장암
Colon/rectal cancer arising via the adenoma-carcinoma sequence
- How common
- 3rd most common cancer in Korea (combined)
- Typical age
- Ages 50–70 (early-onset rising)
What is it?
APC mutation initiates adenoma; KRAS and TP53 mutations accumulate to invasive adenocarcinoma (Vogelgram).
Commonly affected: Colon (left-sided predominant), rectum. Liver mets in 50%
How it develops
- APC mutationWnt pathway activation, aberrant crypt foci
- Adenoma formationKRAS mutation drives small→large adenomas
- High-grade dysplasia → invasionTP53 loss enables basement membrane invasion
- Lymphatic & hepatic metastasisPortal circulation → liver → lung metastasis
Symptoms
- Hematochezia/melenaFresh blood or melena
- Bowel habit changeAlternating constipation/diarrhea, narrow stools
- Iron-deficiency anemiaEspecially right-sided cancers
- Abdominal pain/massCrampy pain, obstructive symptoms
- Weight loss/fatigueSign of advanced disease
How it is examined
- Digital rectal exam50% of rectal cancers palpable on DRE
- Abdominal examAssess for mass, hepatomegaly, ascites
- CEA tumor markerFor prognosis and recurrence monitoring, not diagnosis
Imaging
Abdominal X-ray: obstructive pattern, free air. Chest CT for mets.
- Obstructive pattern
- Liver metastases
Colonoscopy + biopsy for diagnosis. Rectal MRI for T/N staging in rectal cancer. CT/PET-CT for distant evaluation.
- Apple-core sign
- Polypoid mass
- Liver metastases
Non-surgical care
- Staging (TNM, AJCC 8th)CT, MRI (rectum), CEA. Assess nodes/liver/lung
- Molecular markersRAS-WT: cetuximab/panitumumab; MSI-H: pembrolizumab
- Chemotherapy (FOLFOX/FOLFIRI)FOLFOX (5-FU/LV/oxaliplatin) or FOLFIRI (5-FU/LV/irinotecan)
- Targeted therapyBevacizumab (VEGF), cetuximab/panitumumab (EGFR, RAS-WT only), encorafenib (BRAF V600E)
- Neoadjuvant chemoRT for rectalStage II/III rectal: pre-op 5-FU + RT (TNT preferred)
Conservative options are generally tried first. Medications listed here can have side effects — discuss them with your prescriber.
When surgery is considered
All localized CRC; resection of liver/lung mets in selected metastatic
Procedures that may be discussed
- Right/left hemicolectomy + LN dissection
- Low anterior resection (LAR, rectal)
- Abdominoperineal resection (APR, anal involvement)
- Laparoscopic/robotic approach
- Liver metastasectomy (selected)
Outlook
5-yr survival: I 90%, II 75%, III 55%, IV 15%. Liver metastasectomy: 5-yr 30–50%.