When a person is told about “genetic testing of the tumor,” it is normal to feel confusion and anxiety: what are they going to find? At this point, understanding molecular biomarkers in cancer that they can provide before choosing treatment helps to ground expectations and to better converse with the oncology team, because these results guide therapeutic options according to the tumor profile.
What are molecular biomarkers in cancer?
Molecular biomarkers are measurable signals present in the tumor, in the blood, or other body samples. These can be changes in genes, proteins, or patterns of cell function that describe how the cancer behaves.
In practice, these markers make it possible to identify somatic mutations, alterations in cellular pathways and other molecular diagnostic data that help differentiate tumours that, although they look similar in a traditional image or biopsy, do not respond in the same way to the same treatments.
Most important types of molecular biomarkers
- Genomic biomarkers: Look for changes in tumor DNA, including from circulating tumor DNA.
- Proteomic biomarkers: measure levels or presence of proteins that the tumor produces or expresses.
- Epigenetic biomarkers: review modifications that change gene expression without altering the DNA sequence.
These categories complement each other. A well-selected panel can clarify what is “moving” tumor growth and which pathways might be blocked with targeted therapies.
Difference between prognostic and predictive biomarkers
- Prognosis: they help estimate the evolution of the disease (risk of metastasis, probability of relapse, aggressiveness).
- Predictive: indicate whether there is a greater or lesser probability of response to a particular treatment.
Separating these two ideas avoids misunderstandings: a marker may suggest a good prognosis and, at the same time, not indicate a specific therapy; or vice versa, to indicate a clear therapeutic option even if the prognosis is reserved.
How molecular biomarkers are obtained
Biomarkers are evaluated from samples, and the choice of method depends on the type of cancer, the site of the tumor, the availability of tissue, and the clinical goal (diagnosis, treatment selection, follow-up, or search for therapeutic resistance).
Molecular analysis in tumor tissue
The study of tumor tissue by biopsy continues to be a central reference when a broad characterization is needed. With next-generation sequencing and bioinformatic analysis, a set of somatic mutations and potential relevant molecular targets can be identified.
It also allows you to see the context of the tumour: proportion of tumour cells, sample quality and other elements that influence the interpretation of the result.
Liquid biopsy as a non-invasive alternative
Liquid biopsy analyzes markers in the blood and is often an attractive option when tissue is not easy to collect, when frequent monitoring is required, or when the tumor is suspected to have changed over time. In several types of cancer , high agreement with tissue findings has been described, with clear advantages for follow-up
It does not always replace tissue, but it does add value when looking for quick information on current mutations or when the tumour is heterogeneous and not everything is reflected in a single biopsy.
circulating tumor DNA (ctDNA and cfDNA)
Circulating free DNA (cfDNA) is DNA that circulates in the blood and comes from different cells in the body. Circulating tumor DNA (ctDNA) is the fraction of cfDNA that comes from the tumor.
Analyzing ctDNA can show:
- active somatic mutations,
- early signs of therapeutic resistance,
- Presence of residual molecular disease after treatment.
Circulating Tumor Cells: Detection and Analysis
Circulating tumor cells are cancer cells that break off from the tumor and travel through the blood. Its detection and characterization can provide clues about metastatic risk and about biological changes that appear during treatment.
In some scenarios, combining them with circulating tumor DNA offers a more complete view of tumor behavior.
Information provided by biomarkers before treatment
In the therapeutic planning phase, biomarkers help answer practical questions: which routes to drive or block, which options are most likely to work, and what risks of resistance exist.
Identifying Molecular Targets for Targeted Therapies
A central goal of molecular diagnostics is to find molecular targets, such as receptors or signaling pathways, against which targeted therapies exist. If the tumor relies on a particular pathway to grow, blocking it may be more effective than a general approach.
This type of information also serves to avoid treatments with little likelihood of benefit when the tumor is not properly targeted.
Prediction of response to immunotherapy
In some cancers, markers such as PD-L1 expression or tumor mutational burden are associated with a higher probability of response to immunotherapy. They are not “guarantees”, but they guide the balance between expected benefits and risks.
When these markers are low or unfavorable, the treating team may evaluate alternatives, combinations, or different strategies depending on the clinical context.
Detection of relevant somatic mutations
Somatic mutations may suggest susceptibility or resistance to treatments. Detecting them early avoids wasting time with options that the tumor is likely to dodge and helps to choose schemes with more biological logic.
It also allows changes that appear over time to be identified, especially in advanced disease, where the tumour can evolve under the pressure of treatment.
Evaluation of tumor prognosis and aggressiveness
Certain genetic profiles and signatures are associated with more aggressive behaviors, increased risk of metastasis, or increased likelihood of recurrence. Studies have shown how molecular analyses provide useful prognostic signals in specific scenarios
This information does not replace clinical evaluation, but it does add an objective layer to estimate risks and plan management.
Molecular biomarkers according to the type of cancer
Each tumor has “blind spots” and frequent markers. That is why there is no single universal panel: it is selected according to the affected organ, the histological type and the therapeutic options available.
Biomarkers in lung cancer for precision medicine
In lung cancer, mutations in EGFR, ALK, ROS1, and KRAS often guide treatment decisions. This approach underpins precision medicine: assigning targeted therapies when there is an actionable alteration and adjusting the strategy when there is not.
It is also a field where follow-up with liquid biopsy can detect changes associated with therapeutic resistance early.
Applications in Metastatic Breast Cancer
In metastatic breast cancer, markers such as HER2, hormone receptors, and mutations in PIK3CA help to choose between classes of treatment. Monitoring with circulating tumor DNA can support the evaluation of residual molecular disease and changes during the therapeutic course, especially if access to tissue is limited.
Usefulness in pancreatic cancer and early detection
Pancreatic cancer is usually diagnosed late, and that complicates management. Molecular biomarkers such as KRAS and BRCA can provide prognostic information and guide intensified screening strategies in people at high risk, according to clinical and family criteria.
How they influence the selection of individualized treatment
Biomarkers do not “decide” on their own, but they change the conversation: they allow you to choose more precisely between options with different mechanisms and adjust the plan according to evidence of the tumor itself.
Choosing Chemotherapy, Targeted Therapies, or Immunotherapy
The molecular profile may indicate:
- whether it is appropriate to prioritise chemotherapy when there are no clear targets,
- if there are molecular targets that warrant targeted therapies,
- if the immunological pattern suggests benefit with immunotherapy.
The final decision integrates stage, symptoms, comorbidities, treatment goals, and patient preferences, but the molecular component reduces uncertainty in many cases.
Prevention of therapeutic resistance
Part of the value of molecular monitoring is detecting signs of therapeutic resistance when they are not yet seen in images. Research shows that molecular monitoring can warn of emerging resistance in advance compared to conventional radiological methods
When a resistance mutation appears, the team can adjust the plan with line changes, combinations, or new strategies as appropriate.
Dose adjustment and treatment schedules
Some biomarkers relate to how the body processes or responds to certain drugs (pharmacokinetics and pharmacodynamics). That information can guide dose adjustments, intervals, and toxicity monitoring, with the goal of maintaining efficacy without overpunishing the patient.
Limitations of molecular biomarkers
Although they are powerful tools, their results have conditions and margins of error. Interpreting them well requires clinical context and technical quality.
Sensitivity and specificity in molecular diagnostics
There are tests that may not detect variants present in low quantities (limited sensitivity) or confuse benign variants with pathological ones (specificity problems). This is most noticeable when the sample has little tumor material or when the tumor releases little DNA into the bloodstream.
Need for standardization of detection techniques
Different platforms and labs may report results differently. The standardization of methods, criteria and reports, together with a rigorous bioinformatic analysis, is key to compare studies and support therapeutic decisions.
Factors that may affect results
Among the influencing factors are:
- time between sample collection and processing,
- storage conditions,
- quality of the extracted DNA,
- technical interferences and sequencing depth.
A “negative” result does not always mean total absence of alterations; sometimes it reflects the limits of the method or the sample.
Future of biomarkers in oncology
The trend aims to integrate more layers of information in less time, with more sensitive tests and clearer readings for clinical management.
Advances in sensing techniques and technologies
Methods that combine imaging and molecular biology are being investigated, including PET-CT with increasingly specific tracers, and multi-omics approaches that bring together genomics, proteomics and metabolomics to profile the tumor in greater detail.
Integration with genetic analysis and next-generation sequencing
Next-generation sequencing, supported by more robust bioinformatic analysis, allows for broader panels and finer predictive algorithms. The junction between computed tomography and molecular signals is also studied for non-invasive monitoring of therapeutic response
Frequently Asked Questions About Molecular Biomarkers
¿Todos los pacientes con cáncer necesitan análisis de biomarcadores?
Not always. It depends on the type of cancer, the stage, whether there are targeted therapies or immunotherapy with molecular criteria, and whether the result would change the therapeutic plan. In some tumors, the analysis is almost standard; in others, it is reserved for advanced illness or relapses.
¿Qué diferencia hay entre cfDNA y ctDNA en el análisis bioinformático?
cfDNA includes DNA that is free from many sources in the body, while ctDNA is the fraction that comes from the tumor. The bioinformatic analysis seeks to distinguish real tumor signals from normal biological “noise”, to avoid false positives and report variants with clinical relevance.
¿Los biomarcadores pueden predecir efectos secundarios del tratamiento?
Some do. There are markers associated with an increased risk of toxicity or particular susceptibility, especially when the therapeutic target is also expressed in healthy tissues. When that risk is identified, the team can adjust surveillance, dosage, or choose alternatives, depending on the clinical situation.
¿Cuánto tarda un resultado de biomarcadores y qué puede retrasarlo?
The time varies by type of test and laboratory. It may be extended if the sample has a small amount of tumor, if the quality of the DNA is low, or if additional tests are required to confirm findings. It also influences whether a wide panel is made with next-generation sequencing.
¿Qué pasa si el panel no encuentra mutaciones accionables?
A result without actionable mutations does not mean that “there is nothing to be done”. It means that, with current tools, a clear target for targeted therapies was not identified. In these cases, chemotherapy, immunotherapy according to available markers, radiotherapy if applicable, and in certain scenarios, participation in clinical studies if there are options in the country or in the region are evaluated.
¿La biopsia líquida puede reemplazar la biopsia de tejido?
In some cases it can complement and, in specific situations, reduce the need for repeated invasive biopsies. Even so, tissue remains key when histological diagnosis, evaluation of the tumor microenvironment is required, or when the blood does not show sufficient circulating tumor DNA.
Being clear about the scope and limits of these tests helps to interpret the report without unnecessary alarms and to focus on what does guide the therapeutic plan. In Panama, the most useful thing to do is usually to talk with the treating team about which marker changes a particular decision and which only provides clinical context. With this approach, molecular study becomes a practical tool and not just a list of acronyms.
Choosing wisely requires understanding molecular biomarkers in cancer, what information they can provide before choosing treatment.
