A distinction is made in colon carcinoma (colorectal cancer) between an examination program for early detection – colorectal cancer screening – and an examination program for confirming the diagnosis. In addition, several examinations are required preoperatively, i.e., before a planned operation – see Medical Device Diagnostics.
Laboratory parameters of the 1st order – obligatory laboratory examinations.
- CEA (carcinoembryonic antigen).
- CEA level is an independent prognostic tumor marker and should therefore be determined preoperatively
- In follow-up determination of CEA every two to three months in the first two years.
Laboratory parameters 2nd order (diagnostics, follow-up/therapy control).
- CCSA (colon cancer-specific antigen-3, CCSA-4) – this test for colon cancer proteins in the blood can detect 91 percent of disease.
- CA 19-9 (carbohydrate antigen 19-9) – elevated in circa 70% of cases (but not specific for carcinoma of the gastrointestinal tract)The parameter does not increase the informative value regarding the presence of recurrence (recurrence of the disease) compared to CEA value determination alone.
- Molecular genetic testing in suspected cases:
- Hereditary Non-Polyposis Colorectal Carcinoma (HNPCC) – autosomal dominant inheritance with 80% penetrance; early age of manifestation (median age at diagnosis: 45 years); frequent synchronous/metachronous second cancers of the colon and rectum; currently, four genes (MLH1, MSH2, MSH6, PMS2) have been identified whose germline mutations are responsible for the occurrence of HNPCC.
- Familial Adenomatous Polyposis (FAP).
- Peutz-Jeghers syndrome (PJS)
- Juvenile Polyosis Coli (JPC)
- BRAF status: BRAF mutations are associated with a worse prognosis than BRAF wild-type tumors in colorectal cancer.
- RAS biomarker test (blood-based procedure; OnkoBEAM test)-monitor RAS mutation status during ongoing therapy; the RAS gene plays a central role in controlling cancer cell growth and is critical in selecting targeted therapyNote: Current gold standard for determining RAS status is tissue biopsy.
- Detection of microsatellite (MIS) instability by genotyping and quantification of tumor mutation burden (TMB) by next generation sequencing – in metastatic colorectal cancer possibly in the future already in first-line therapy [negative factor: low TMB]In one study it was shown that in MSS tumors (MSI-stable tumors, 93% of patients) the expression of TMB has an impact on prognosis
- KI-67 (KI67; synonym: MIB1, proliferation marker for objectification and validation of grading, allows conclusions on growth behavior) [strong expression of Ki-67: risk of death increased by 50%; if the cutoff for a KI-67 positive finding was 20-30% positive cells, this correlated with a doubled mortality rate].
- Liquid biopsy: circulating tumor DNA fragments (ctDNA) in blood.
- Screening for mutations in RAS genes in metastatic colorectal cancer to predict response to EGFR monoclonal antibodies; is certainly becoming the new gold standard: with the help of DNA analysis, significantly more mutations have been detected than by tissue biopsy; another advantage is the speed of evaluation (only 2 days)
- Evidence of recurrence risk after surgical resection in stage II patients or indication for chemotherapy? Further results to be awaited.
Cancer early detection measures (KFEM)
- ≥ 50 years of age: annual test for fecal occult (invisible) blood (immunological FOBT (iFOBT)).
- ≥ 55 years of age: every 2 years test for occult blood in the stool, alternatively a maximum of 2 colonoscopies at intervals of 10 years.
