XpertPatient Cancer Centers

Understanding Cancer Biomarkers
Your Guide to Smarter Care

From diagnosis to treatment selection, biomarkers are transforming what's possible in cancer care. Learn what they mean for you.

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What Is a Cancer Biomarker?

The U.S. National Cancer Institute (NCI) defines a biomarker as "a biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease." Put simply — it's a measurable signal your body produces that tells doctors important things about a cancer.

Biomarkers can be proteins, genes, chromosomes, hormones, or even patterns of gene activity. They go well beyond traditional tumor markers like PSA or CA-125. Today, biomarkers guide whether a specific treatment will work for your tumor — not just any tumor of the same type. This is the foundation of precision oncology.

When your oncologist orders biomarker testing, they're building a molecular fingerprint of your cancer. That fingerprint can reveal which therapies are likely to help, which to avoid, whether the cancer may return, and how aggressively it may behave.

🔍 Diagnostic Biomarkers

Help confirm a cancer diagnosis or identify the type and subtype of cancer present.

📊 Prognostic Biomarkers

Predict how a cancer is likely to behave over time — whether it may spread or recur — independent of treatment.

🎯 Predictive Biomarkers

Indicate how likely a cancer is to respond to a particular treatment, such as targeted therapy or immunotherapy.

📈 Monitoring Biomarkers

Track how well a treatment is working or detect cancer recurrence during and after treatment.

Testing Methods

How Are Biomarkers Tested?

Biomarker testing uses several methods depending on what is being measured. Your care team selects the right approach for your cancer type.

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Tissue Biopsy & IHC

Immunohistochemistry (IHC) on tumor tissue. The standard method for ER, PR, HER2, PD-L1, and many others.

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Blood / Serum Tests

PSA, AFP, CA 19-9, beta-2 microglobulin and other proteins are measured directly from a blood sample.

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Molecular / NGS Testing

Next-generation sequencing identifies gene mutations (KRAS, BRAF, EGFR, BRCA) with high precision from tumor tissue or blood.

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Liquid Biopsy

Detects circulating tumor DNA (ctDNA) or cells in blood — useful for monitoring and when tissue biopsy isn't possible.

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FISH / Cytogenetics

Fluorescence in situ hybridization detects gene amplifications and rearrangements like HER2 amplification or ALK rearrangement.

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Flow Cytometry

Used in blood cancers to identify cell surface markers like CD20 in lymphoma, supporting diagnosis and treatment selection.

Cancer Centers

Biomarkers by Cancer Type

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Breast Cancer Biomarkers

Hormone receptor and HER2 status are the cornerstone of breast cancer treatment planning.

Key Biomarkers Tested

ER Estrogen Receptor status — guides whether hormone (endocrine) therapy like tamoxifen will be effective.
PR Progesterone Receptor — alongside ER, shapes hormone therapy decisions and helps predict treatment response.
HER2/neu HER2-positive tumors grow more aggressively but respond to targeted drugs like trastuzumab (Herceptin).
Ki-67 Measures how rapidly tumor cells are dividing — a higher score means a faster-growing tumor.
BRCA1/2 Hereditary gene mutations that raise cancer risk and may qualify patients for PARP inhibitor therapy.
Source: ARUP Consult — Breast Cancer

Suggested Videos

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HER2, ER & PR in Breast Cancer Explained Search: Memorial Sloan Kettering / Mayo Clinic
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BRCA1 & BRCA2 Genetic Testing Guide Search: NCI / Dana-Farber Cancer Institute
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Reading Your Breast Cancer Pathology Report Search: Susan G. Komen / Breastcancer.org

💡 Tip: Search YouTube for the video title + "Mayo Clinic" or "MSK" for highest-quality, medically reviewed content.

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Prostate Cancer Biomarkers

PSA remains central, but newer biomarkers are reducing unnecessary biopsies and guiding treatment.

Key Biomarkers Tested

PSA Prostate-Specific Antigen — used for screening, diagnosis, and monitoring treatment response or recurrence.
PCA3 A urine-based diagnostic biomarker that helps determine whether a prostate biopsy is needed after elevated PSA.
TMPRSS2-ERG A gene fusion marker found in about 50% of prostate cancers — under research as a diagnostic and therapeutic target.
AR Androgen Receptor status — indicates hormone sensitivity and guides the use of androgen-deprivation therapy.
Source: NIH / PMC — Prostate Cancer Biomarkers

Suggested Videos

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Understanding the PSA Test Search: Mayo Clinic / American Cancer Society
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Genomic Biomarker Tests for Prostate Cancer Search: PCF Prostate Cancer Foundation
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Hormone Therapy & Androgen Receptor in Prostate Cancer Search: ASCO / Johns Hopkins Medicine
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Lung Cancer Biomarkers

Comprehensive biomarker testing has transformed lung cancer into one of the most targetable cancers.

Key Biomarkers Tested

EGFR Mutations in the EGFR gene make the tumor responsive to EGFR inhibitors like erlotinib or osimertinib.
ALK ALK gene rearrangements define a subgroup eligible for highly effective ALK inhibitors like crizotinib or alectinib.
KRAS The most common mutation in lung adenocarcinoma. KRAS G12C mutations can now be targeted with sotorasib.
PD-L1 High PD-L1 expression indicates a greater likelihood of responding to checkpoint immunotherapy (pembrolizumab).
TP53 A tumor suppressor gene; mutations are common and carry prognostic significance.
Source: NIH / PMC — Lung Cancer Biomarkers

Suggested Videos

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Lung Cancer Biomarker Testing: Why It Matters Search: LUNGevity / ASCO
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PD-L1 & Immunotherapy in Lung Cancer Search: Memorial Sloan Kettering
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KRAS Mutations & New Targeted Therapies Search: Moffitt Cancer Center / NCI
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Bladder Cancer Biomarkers

FGFR3 testing is opening a new era of targeted treatment for bladder cancer patients.

Key Biomarkers Tested

FGFR3 Mutations or fusions in the FGFR3 gene are targeted by erdafitinib — a precision therapy for bladder cancer.
TP53 A tumor suppressor; TP53 alterations in bladder cancer carry prognostic significance and signal higher-grade disease.
PD-L1 PD-L1 expression is tested to determine eligibility for immunotherapy with atezolizumab or pembrolizumab.
Source: NIH / PMC — Bladder Cancer Biomarkers

Suggested Videos

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FGFR3 & Targeted Therapy in Bladder Cancer Search: BCAN Bladder Cancer Advocacy Network
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Immunotherapy for Bladder Cancer — Patient Overview Search: American Cancer Society / ASCO
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Colon Cancer Biomarkers

RAS/RAF mutation testing and mismatch repair status are essential before starting treatment.

Key Biomarkers Tested

KRAS/NRAS Mutations in RAS genes predict resistance to EGFR-targeting antibodies like cetuximab — must be tested before therapy.
BRAF BRAF V600E mutation is prognostic and identifies patients who may benefit from BRAF/MEK inhibitor combinations.
MSI-H/dMMR High microsatellite instability or deficient mismatch repair makes tumors highly responsive to checkpoint immunotherapy.
Source: NIH / PMC — Colon Cancer Biomarkers

Suggested Videos

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MSI-H & Immunotherapy in Colorectal Cancer Search: Colorectal Cancer Alliance / ASCO
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KRAS, BRAF & RAS Testing in Colorectal Cancer Search: MD Anderson / Mayo Clinic
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Endometrial Cancer Biomarkers

Molecular classification of endometrial cancer now guides treatment intensity and immunotherapy eligibility.

Key Biomarkers Tested

PTEN The most commonly mutated tumor suppressor in endometrial cancer; loss of PTEN drives PI3K pathway activation.
PIK3CA Activating mutations in the PI3K pathway are common and under investigation as therapeutic targets.
MSI-H/dMMR About 25% of endometrial cancers show mismatch repair deficiency, making them candidates for pembrolizumab therapy.
Source: NIH / PMC — Endometrial Cancer Biomarkers

Suggested Videos

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Molecular Testing in Endometrial Cancer Search: SGO Society of Gynecologic Oncology / MSK
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Immunotherapy for Uterine Cancer — Who Qualifies? Search: ASCO / American Cancer Society
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Kidney (Renal) Cancer Biomarkers

VHL gene status and angiogenesis markers shape targeted therapy choices in renal cell carcinoma.

Key Biomarkers Tested

VHL Loss of the VHL tumor suppressor gene is found in most clear cell renal carcinomas and drives VEGF pathway activity.
CA9 Carbonic anhydrase 9 is a prognostic marker — high expression correlates with VHL loss and tumor hypoxia response.
PD-L1 PD-L1 expression helps guide immunotherapy combination approaches like nivolumab + ipilimumab.
Source: ASCO — Kidney Cancer Biomarkers

Suggested Videos

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Targeted Therapy & VHL in Kidney Cancer Search: KCCure / Cleveland Clinic
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Immunotherapy Combinations in Kidney Cancer Search: Kidney Cancer Association / ASCO
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Leukemia Biomarkers

Genetic and chromosomal biomarkers have made leukemia one of the most precisely classified blood cancers.

Key Biomarkers Tested

BCR-ABL1 The "Philadelphia chromosome" fusion gene — the defining marker of CML and target for imatinib (Gleevec).
FLT3 FLT3 mutations in AML are associated with poorer prognosis and are targeted by midostaurin and gilteritinib.
NPM1 NPM1 mutations in AML are generally favorable prognostic markers and guide treatment intensity decisions.
Source: NIH / NBK — Leukemia Biomarkers

Suggested Videos

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BCR-ABL & Targeted Therapy in CML Search: Leukemia & Lymphoma Society
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AML Genetic Mutations — FLT3 & NPM1 Search: MD Anderson / LLS
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Liver Cancer Biomarkers

AFP remains the most established liver cancer biomarker for monitoring disease burden and response.

Key Biomarkers Tested

AFP Alpha-fetoprotein — the primary blood marker for hepatocellular carcinoma. Used for diagnosis and monitoring treatment response.
GPC3 Glypican-3 is a tumor-associated protein and emerging target for antibody-based therapies in liver cancer.
TP53 TP53 mutations carry negative prognostic weight in liver cancer and are associated with aggressive tumor behavior.
Source: NCI — Liver Cancer Treatment (PDQ)

Suggested Videos

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AFP & Liver Cancer Diagnosis Explained Search: American Liver Foundation / NCI
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Liver Cancer Treatment Overview for Patients Search: Mayo Clinic / MD Anderson
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Melanoma Biomarkers

BRAF V600E is one of the most actionable mutations in cancer — present in about half of all melanomas.

Key Biomarkers Tested

BRAF V600E The most important melanoma biomarker — this mutation responds to BRAF inhibitors (vemurafenib, dabrafenib) with significant benefit.
NRAS NRAS mutations are found in ~20% of melanomas. They are prognostic and under investigation for MEK inhibitor targeting.
PD-L1 High PD-L1 expression supports immunotherapy with checkpoint inhibitors like pembrolizumab or nivolumab.
Source: American Cancer Society — Melanoma

Suggested Videos

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BRAF Mutation & Targeted Therapy in Melanoma Search: Melanoma Research Foundation / MSK
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Immunotherapy Revolution in Melanoma Search: AIM at Melanoma / ASCO
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Multiple Myeloma Biomarkers

Protein markers and free light chains are the backbone of myeloma monitoring and response assessment.

Key Biomarkers Tested

M Protein The monoclonal protein secreted by myeloma cells — a direct measure of disease burden and central to diagnosis and monitoring.
Beta-2 Micro Beta-2 microglobulin is a key prognostic biomarker — higher levels correlate with more advanced disease staging.
FLC Free Light Chains (kappa and lambda) are used for diagnosis, monitoring, and detecting disease recurrence.
Source: American Cancer Society — Multiple Myeloma

Suggested Videos

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M Protein & SPEP in Multiple Myeloma Search: IMF Myeloma Foundation / Dana-Farber
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Free Light Chains & Myeloma Monitoring Search: Multiple Myeloma Research Foundation
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Non-Hodgkin Lymphoma Biomarkers

CD20 status unlocks access to rituximab — one of the most successful targeted therapies ever developed.

Key Biomarkers Tested

CD20 A surface protein on B-cells; CD20-positive lymphomas respond to rituximab and next-generation anti-CD20 antibodies.
BCL2 BCL2 overexpression protects lymphoma cells from programmed death — now targeted by venetoclax in select cases.
MYC MYC rearrangements, especially combined with BCL2 ("double-hit"), define aggressive lymphoma requiring intensified treatment.
Source: American Cancer Society — NHL

Suggested Videos

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CD20 & Rituximab in Non-Hodgkin Lymphoma Search: LLS Leukemia & Lymphoma Society
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Double-Hit Lymphoma — MYC & BCL2 Explained Search: Lymphoma Research Foundation / MSK
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Pancreatic Cancer Biomarkers

BRCA testing has opened targeted treatment options for pancreatic cancer patients with hereditary risk.

Key Biomarkers Tested

CA 19-9 The primary blood marker for pancreatic cancer — used to track treatment response and monitor for progression or recurrence.
KRAS Mutated in over 90% of pancreatic cancers — a defining driver mutation and emerging therapeutic target.
BRCA1/2 BRCA-mutated pancreatic cancers respond to PARP inhibitors like olaparib — all patients should be tested for germline mutations.
Source: American Cancer Society — Pancreatic Cancer

Suggested Videos

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BRCA & PARP Inhibitors in Pancreatic Cancer Search: Pancreatic Cancer Action Network / ASCO
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CA 19-9 Tumor Marker — What It Tells Us Search: Mayo Clinic / Pancreatic Cancer Action Network
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Rectal Cancer Biomarkers

Rectal cancer shares many biomarkers with colon cancer — RAS mutation and MMR status guide every treatment plan.

Key Biomarkers Tested

KRAS/NRAS Like colon cancer, RAS mutation status in rectal cancer predicts lack of response to anti-EGFR therapies and must be tested first.
MSI-H/dMMR MSI-H rectal cancers respond well to immunotherapy — recent data show neoadjuvant PD-1 blockade can achieve complete responses.
TP53 TP53 mutations are common in rectal cancer and serve as a prognostic indicator of tumor biology.
Source: American Cancer Society — Colorectal Cancer

Suggested Videos

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Immunotherapy in Rectal Cancer — Complete Response Search: ASCO / MSK Memorial Sloan Kettering
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Biomarker Testing Before Starting CRC Treatment Search: Fight Colorectal Cancer / ASCO

Common Questions

Biomarker FAQs

Will my insurance cover biomarker testing?

Most major insurers and Medicare cover biomarker testing when it is ordered as part of cancer diagnosis or to guide treatment decisions. The ACCESS to Cancer Biomarker Testing Act and CMS policies have expanded coverage for FDA-approved biomarker tests. Always ask your care team or insurance coordinator before testing.

Can I have biomarker testing done at any lab?

Biomarker tests are typically performed on tumor tissue collected during biopsy or surgery, sent to a specialized pathology or molecular lab. Some blood-based biomarker tests (liquid biopsy, PSA, AFP) can be done at most clinical labs. Your oncologist will order the appropriate tests and labs.

What if my biomarker test comes back negative or inconclusive?

A negative result on a specific biomarker simply means that particular treatment target isn't present — other options are still available. An inconclusive result may warrant retesting on additional tissue. Always discuss results thoroughly with your oncologist.

Can biomarkers change over time?

Yes. Cancers can evolve, and biomarkers can change — especially after treatment. This is why repeat testing (including liquid biopsy) may be recommended when cancer progresses or recurs to identify new treatment options.

Should I ask for comprehensive genomic profiling (CGP)?

CGP tests hundreds of biomarkers simultaneously and is increasingly recommended for many advanced cancers. It can uncover actionable mutations that individual tests might miss. Ask your oncologist whether a CGP panel is appropriate for your situation.

Know Your Biomarkers. Own Your Journey.

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XpertPatient Cancer Centers — Biomarker Resource Guide

This page is for educational purposes only and does not constitute medical advice.
Always consult your oncology team before making treatment decisions.

Sources: NCI, American Cancer Society, ARUP Consult, ASCO, NIH/PMC, Cancer.gov