Can cancer genome tests guide therapy in colon cancer patients?

Question

Hello doctor,

My father, 62, was recently diagnosed with metastatic colon cancer, and his oncologist suggested cancer genome testing to guide treatment.

We have heard it can help identify targeted therapies, but we are unsure about the cost, accuracy, and what happens if no actionable mutations are found. How often does genetic testing actually change the treatment plan, and how quickly do results usually come back?

Kindly help.

Thank you.

Answer 1

Hello,

Welcome to icliniq.com.

I read your query and understood your concern.

The cancer genome testing usually refers to tumor genomic profiling, also called NGS (next-generation sequencing).

Somatic tumor mutations occur only in the cancer and can guide targeted therapies, immunotherapy, and clinical trial options.

Common genes in colon cancer include the following:

KRAS (Kirsten rat sarcoma).
NRAS (neuroblastoma rat sarcoma).
BRAF (v-raf murine sarcoma viral oncogene homolog B1).
HER2 (human epidermal growth factor receptor 2) amplification.
NTRK (neurotrophic tyrosine receptor kinase) fusion.
MSI-H (microsatellite instability-high).
dMMR (deficient mismatch repair) status.
PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha).

Germline hereditary mutation checks for inherited risks such as Lynch syndrome. It is important for the patient and family, but it does not always change treatment.

In metastatic colorectal cancer, about 20 to 30 percent of patients have actionable findings that meaningfully change therapy. Such as:

MSI-H (microsatellite instability-high) or dMMR (deficient mismatch repair), about five percent, qualify for immunotherapy such as Pembrolizumab or Nivolumab.
HER2 (human epidermal growth factor receptor 2) amplification, about three to five percent, qualifies for HER2-targeted therapy.
BRAF V600E (v-raf murine sarcoma viral oncogene homolog B1), about eight percent, qualifies for BRAF-targeted combinations.
NTRK (neurotrophic tyrosine receptor kinase) fusion, less than one percent, qualifies for TRK (tropomyosin receptor kinase) inhibitors.
RAS wild-type tumors can receive EGFR (epidermal growth factor receptor) inhibitors such as Cetuximab or Panitumumab.

When applicable, these findings can dramatically influence the treatment path.

If no actionable mutation is found: This is very common.

If no targetable mutation appears, standard treatment options include chemotherapy combinations such as FOLFOX (Folinic acid/Fluorouracil/Oxaliplatin) or FOLFIRI (Folinic acid/Fluorouracil/Irinotecan).
Targeted therapy based on RAS (rat sarcoma) status, such as EGFR (epidermal growth factor receptor) inhibitors, is used only if RAS is wild-type.
Anti-VEGF (vascular endothelial growth factor) therapy, such as Bevacizumab, is used broadly regardless of mutations.
Immunotherapy is used only if MSI-H (microsatellite instability-high) or dMMR (deficient mismatch repair) is positive.
Even if nothing actionable shows up, the testing predicts what not to use, such as a KRAS (Kirsten rat sarcoma) mutation, meaning no EGFR inhibitors.

Testing also helps determine clinical trial eligibility. A negative result still has clinical value.

Accuracy of genomic testing:

Modern NGS tests are highly accurate. Sensitivity is approximately 95 to 99 percent for detecting most mutation types. Specificity is approximately 99 percent, meaning false positives are extremely low.

Accuracy depends on tumor tissue quality, tumor cellularity, and whether a blood-based liquid biopsy or a tissue sample is used. Tissue is slightly more accurate. Blood is faster and easier, but may miss low-volume mutations. Most oncologists start with tissue testing if available.

I hope that this answers your query.

Kindly follow up if you have more doubts.

Thank you.