Targeted Cancer Therapy: Genetic Testing and Treatment Matching

Targeted cancer therapy is a treatment approach that uses information about a person’s cancer cells to help select medicines more precisely. Genetic and biomarker testing can identify changes in a tumor that may guide treatment choices, clinical trial options, or monitoring plans.

Overview

Targeted cancer therapy is part of precision oncology, a field that uses detailed information about a tumor to help guide treatment. Instead of choosing therapy only by where the cancer started, such as breast, lung, colon, or skin, doctors may also look for specific genetic changes, proteins, or other biomarkers that are driving cancer growth. When a relevant target is found, a medicine may be selected to block that signal or weaken the cancer cell’s ability to survive.

This approach does not replace traditional cancer care. Surgery, radiation therapy, chemotherapy, immunotherapy, hormone therapy, and supportive treatments may still be important, depending on the cancer type and stage. Targeted therapy is often used together with other treatments or after certain treatments have already been tried.

For patients, the main idea is treatment matching: finding out whether the cancer has a feature that can be acted on. This usually requires genetic testing for cancer, also called tumor profiling, molecular testing, genomic testing, or biomarker testing. The results can help the oncology team recommend a specific treatment, avoid treatments that are unlikely to help, or suggest a clinical trial when appropriate.

How Targeted Therapy Works

Cancer cells often grow because of changes in genes that control cell division, repair, and survival. Some changes act like a stuck accelerator, telling cancer cells to keep multiplying. Others may turn off natural safety systems that normally repair damage or stop abnormal cells from growing. Targeted therapies are designed to interfere with these abnormal signals or with proteins the cancer depends on.

Different targeted medicines work in different ways. Some are small-molecule drugs that enter cells and block enzymes involved in growth signaling. Others are monoclonal antibodies that attach to targets on the surface of cancer cells or help deliver treatment more directly. Some targeted treatments block the formation of blood vessels that feed tumors, while others affect DNA repair pathways in cancers with specific repair defects.

Targeted therapy is not the same as chemotherapy, although both are drug treatments for cancer. Chemotherapy generally affects rapidly dividing cells, including some healthy cells, which is why side effects such as hair loss or low blood counts can occur. Targeted therapy is more focused on a molecular feature, but it can still affect normal tissues and cause side effects such as rash, diarrhea, liver enzyme changes, blood pressure changes, fatigue, or heart-related effects, depending on the drug.

Genetic Testing and Biomarker Testing

Testing may look at DNA, RNA, proteins, or other tumor characteristics. A tissue test uses a sample from a biopsy or surgery to study the tumor directly. A blood-based test, sometimes called a liquid biopsy, may look for tumor DNA circulating in the bloodstream. Liquid biopsy can be useful when tissue is hard to obtain, but it may not detect all findings, so the oncology team decides which test is most appropriate.

It is helpful to distinguish tumor testing from inherited genetic testing. Tumor testing looks for changes that developed in the cancer cells and are usually not passed down to children. Inherited, or germline, testing looks for genetic variants present in all cells of the body that may affect cancer risk in a family. Sometimes both types of testing are recommended, especially if tumor results suggest an inherited risk or if the patient’s personal or family history is relevant.

Common testing approaches include single-gene tests, panels that examine many cancer-related genes, immunohistochemistry to measure certain proteins, in situ hybridization to detect gene rearrangements or amplifications, and next-generation sequencing panels. The best test depends on the cancer diagnosis, stage, available tissue, prior treatments, and whether the result is likely to change management.

What Test Results Can Mean

Results may identify an actionable biomarker, meaning a finding that may guide an approved treatment, a treatment used in a specific cancer setting, or a clinical trial. Examples can include gene mutations, gene fusions, amplifications, mismatch repair deficiency, microsatellite instability, hormone receptors, or overexpression of specific proteins. The meaning of a biomarker depends strongly on the cancer type and the clinical situation.

A positive result does not automatically mean a targeted therapy will be recommended. The medicine must be suitable for the patient’s cancer type, stage, previous treatments, overall health, and treatment goals. In some cases, a biomarker is linked to a drug only for certain cancers. In other cases, a targeted medicine may be approved across multiple tumor types if a specific molecular feature is present.

A negative or inconclusive result can still be useful. It may rule out certain therapies, show that another treatment approach is better, or indicate that more tissue is needed. Some results are classified as variants of uncertain significance, meaning there is not enough evidence to use them for treatment decisions. Patients should avoid making major choices based only on a report without discussion with a qualified oncology team.

Treatment Matching and Care Planning

Treatment matching usually begins with a confirmed cancer diagnosis and staging. The oncology team reviews pathology results, imaging, blood tests, the patient’s medical history, and any prior treatments. If biomarker testing is indicated, the team selects the test method and sample type, then interprets the results in the context of current clinical guidelines and available medicines.

When a matched therapy is available, doctors discuss expected benefits, possible side effects, how the medicine is taken, monitoring needs, and alternatives. Some targeted medicines are tablets taken at home, while others are given by infusion. Regular follow-up may include physical exams, blood tests, imaging, heart monitoring, skin checks, or other evaluations depending on the treatment.

Sometimes the best option is a clinical trial, especially when a tumor has a rare biomarker, when standard treatments have already been used, or when a promising targeted approach is still being studied. Participation in a clinical trial is voluntary, and patients should receive clear information about the purpose of the study, possible risks and benefits, visits required, and available alternatives.

Benefits, Limits, and Resistance

The potential benefit of targeted therapy is that treatment can be selected based on a feature that is important to the cancer’s growth. For some patients, this can lead to meaningful tumor control and may avoid treatments that are less likely to work. Biomarker testing can also help identify patients who may benefit from immunotherapy or from treatments designed for DNA repair defects.

There are important limits. Not every cancer has an actionable target, and not every target has an available medicine. Even when a matched drug is used, responses vary. A tumor may contain different groups of cells, some more sensitive than others. Over time, cancer cells may develop resistance by acquiring new changes or using alternative growth pathways.

If resistance occurs, repeat testing may sometimes be recommended to look for new targets or resistance mechanisms. The care plan may change to another targeted medicine, immunotherapy, chemotherapy, radiation, surgery, supportive care, or a clinical trial. The goal is to adjust treatment based on how the cancer is behaving and what is safest and most appropriate for the individual patient.

Preparing for Testing and Treatment

Patients can prepare by asking what type of testing is being ordered, whether it uses tumor tissue or blood, and how long results may take. It is also useful to ask whether the test may reveal inherited risk information and whether genetic counseling is recommended. Patients should tell their doctor about all medicines and supplements, allergies, other medical conditions, and any family history of cancer.

Helpful questions include:

• What biomarkers are being tested for this cancer type?
• Could the results change the treatment plan?
• Is there enough tissue from the biopsy, or is another sample needed?
• What are the possible targeted therapy options and side effects?
• Are clinical trials available if no standard matched therapy is found?

During targeted therapy, patients should report side effects early rather than waiting for the next appointment. Many side effects can be managed with dose adjustments, supportive medicines, temporary treatment breaks, or specialist input. Patients should not stop or change a cancer medicine without medical advice unless they have been given specific instructions for urgent symptoms.

When to See a Doctor

People diagnosed with cancer should ask their oncology team whether biomarker or genetic testing is recommended for their cancer type and stage. This is especially important for cancers where testing commonly guides treatment, such as certain lung cancers, breast cancers, colorectal cancers, ovarian cancers, melanomas, gastrointestinal stromal tumors, thyroid cancers, and some blood cancers. Testing recommendations continue to evolve as new evidence becomes available.

Patients should also seek medical advice if they have a strong family history of cancer, cancer diagnosed at a young age, multiple primary cancers, or tumor test results that may suggest an inherited condition. In these situations, referral to a genetic counselor or specialist genetics service may help patients understand personal and family implications.

Acibadem International’s multidisciplinary oncology specialists and JCI-accredited hospitals diagnose and treat cancer for international patients, including the use of molecular testing when clinically appropriate. Decisions about targeted therapy should always be individualized after review by qualified cancer specialists, with clear discussion of benefits, risks, alternatives, and patient preferences.

Frequently asked questions

What is targeted cancer therapy?

Targeted cancer therapy uses medicines designed to interfere with specific molecules, proteins, or genetic changes that help some cancers grow. It is different from standard chemotherapy because it is selected based on a cancer’s biological features. It may be used alone or together with surgery, radiation therapy, chemotherapy, immunotherapy, or hormone therapy.

Does every patient with cancer need genetic testing?

Not every patient needs the same testing. The need for genetic or biomarker testing depends on the cancer type, stage, pathology, treatment goals, and whether results are likely to guide care. An oncology team can explain which tests are recommended and why.

Is tumor genetic testing the same as inherited genetic testing?

No. Tumor genetic testing looks for changes in the cancer cells that usually occurred during a person’s lifetime. Inherited genetic testing looks for variants present in all cells of the body that may affect cancer risk in a family. Sometimes both are recommended, and genetic counseling may be helpful.

What happens if no target is found?

If no actionable target is found, the oncology team may recommend other evidence-based treatments such as chemotherapy, immunotherapy, hormone therapy, radiation, surgery, or supportive care. A negative result can still be useful because it helps narrow the most appropriate options. In some cases, a clinical trial may also be considered.

Can targeted therapy cure cancer?

Targeted therapy can be very important for some cancers, but its purpose depends on the cancer type and stage. In some settings it may be part of curative treatment, while in others it aims to control cancer, reduce symptoms, or delay progression. The treating oncologist can explain the realistic goals for an individual situation.

Are targeted therapies free of side effects?

No. Although targeted therapies are more focused than many traditional treatments, they can still affect healthy tissues. Side effects vary by medicine and may involve the skin, digestive system, liver, heart, lungs, blood pressure, or other organs. Regular monitoring and early reporting of symptoms help the care team manage problems safely.

How should patients read a biomarker test report?

Biomarker reports can be technical and should be reviewed with an oncologist. The most important points are whether an actionable finding was identified, whether there is an approved therapy or clinical trial, and how the result fits the patient’s diagnosis and treatment history. Patients should avoid interpreting uncertain variants as clear treatment targets without expert guidance.

References

• National Cancer Institute
• American Society of Clinical Oncology
• European Society for Medical Oncology
• World Health Organization
• National Comprehensive Cancer Network

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.