Targeted Therapy for Cancer

Introduction

If you or someone close to you has been told that targeted therapy is part of the cancer treatment plan, you are likely trying to understand what this means in practical terms. How is it different from chemotherapy? Why does it depend on testing the tumour? How long will treatment last, what will daily life look like, and what should you watch for?

Targeted therapy is a broad family of cancer treatments designed to interfere with the specific molecules and signals that a particular cancer depends on to grow and spread. It is not one drug. It is dozens of drugs, each matched to a particular molecular feature of a tumour. Which targeted therapy — if any — is suitable depends on the type of cancer, its stage, and the results of tests done on the tumour itself.

This article explains what targeted therapy is, how oncologists decide who may benefit, the main drug classes and how they are given, what the treatment journey usually looks like, the side effects that come with these drugs, and what living with long-term targeted therapy can be like. It is written for patients and families who have a cancer diagnosis and are now planning the next phase of care.

What Is Targeted Therapy?

Targeted therapy is a type of cancer treatment that uses drugs to block specific proteins, genes, or signalling pathways that help cancer cells grow, divide, repair themselves, or form new blood vessels. Because these treatments are aimed at molecular features of the cancer, they are also called molecular targeted therapy or, more broadly, precision oncology.

Traditional chemotherapy works by damaging any cell that divides quickly. This includes cancer cells, but also healthy fast-dividing cells in the bone marrow, hair follicles, mouth, and gut — which is why chemotherapy can cause hair loss, low blood counts, and mouth sores. Targeted therapy takes a different approach. It tries to attack the specific molecular machinery the cancer relies on, while leaving most normal cells largely alone.

The targets of these drugs vary. Some block signals that tell a cancer cell to keep dividing. Others stop tumours from growing the blood vessels they need to expand. Some interfere with the cancer’s ability to repair its damaged DNA. Others mark cancer cells for destruction by the immune system, or carry a toxic payload directly to a cancer cell.

One important point: targeted therapy is not the same as immunotherapy. Immunotherapy works by changing how the immune system responds to cancer. Targeted therapy works directly on cancer-cell biology. The two can sometimes be combined, but they are distinct strategies.

How Targeted Therapy Works

Cancer happens, in simplified terms, when genetic changes inside a cell switch on growth signals that should be off, or switch off the brakes that should keep growth in check. These changes can make a cell divide endlessly, ignore signals to die, invade nearby tissues, or spread through the bloodstream.

• Blocks a growth signal. Some cancers have an abnormal protein on their surface, or an overactive switch inside the cell, that constantly tells the cell to divide. Targeted drugs can attach to this protein or jam this switch so the signal can no longer be sent.
• Cuts off the blood supply. Tumours need new blood vessels to grow beyond a small size. Anti-angiogenic targeted drugs block the signals tumours use to recruit blood vessels, starving the cancer of oxygen and nutrients.
• Interferes with DNA repair. Some cancers have weaknesses in how they repair damaged DNA. Targeted drugs (such as PARP inhibitors) can exploit this weakness so the cancer cell accumulates damage it cannot fix, and dies.
• Triggers cell death. Healthy cells have built-in programmes that tell them when to die. Many cancers have switched these programmes off. Some targeted drugs work by reactivating these natural self-destruct pathways.
• Delivers a toxin directly to the cancer. Antibody-drug conjugates are targeted drugs linked to a powerful chemotherapy agent. The antibody finds the cancer cell, attaches to it, and releases the toxin inside — sparing most healthy tissue.
• Flags the cancer for the immune system. Some monoclonal antibodies attach to cancer cells and signal the immune system to destroy them.

Because each targeted drug works on a specific mechanism, the question oncologists ask is: does this tumour actually depend on that mechanism? That is what biomarker testing answers.

Who Receives Targeted Therapy?

Eligibility for targeted therapy depends on three things: the cancer type, the cancer stage and prior treatments, and the results of biomarker testing on the tumour.

Cancers where targeted therapy is commonly used

Targeted drugs are now part of standard care across many cancer types, including:

• Lung cancer, particularly non-small cell lung cancer with mutations such as EGFR, ALK, ROS1, KRAS, BRAF, MET, RET, and NTRK
• Breast cancer, particularly HER2-positive disease and hormone receptor-positive disease, and breast cancers with BRCA mutations
• Colorectal cancer, particularly those with specific RAS, BRAF, HER2, or microsatellite instability profiles
• Chronic myeloid leukaemia (CML) and certain acute leukaemias, where targeted drugs have transformed outcomes
• Lymphomas, including some B-cell lymphomas treated with anti-CD20 antibodies and BTK inhibitors
• Melanoma, particularly those with BRAF mutations
• Kidney cancer (renal cell carcinoma), where anti-angiogenic targeted drugs are central to treatment
• Liver cancer (hepatocellular carcinoma)
• Ovarian cancer, particularly with BRCA mutations or homologous recombination deficiency
• Prostate cancer, including some advanced cases with BRCA or related mutations
• Gastrointestinal stromal tumours (GIST), which respond strongly to KIT-targeted drugs
• Thyroid cancers with certain mutations
• Pancreatic, bladder, head and neck, and certain brain tumours in selected molecular subgroups

Targeted therapy is particularly important when cancer is advanced or has spread (metastatic), when it has come back after earlier treatment (recurrent), or when standard chemotherapy is not working or not suitable. In some cancers, targeted drugs are also used in earlier stages and after surgery to reduce the risk of recurrence.

Biomarker testing: the key step

Before targeted therapy is chosen, the cancer is usually tested for the specific molecular features that the drug attacks. This is sometimes called biomarker testing, molecular profiling, genomic testing, or tumour profiling. It is typically done on a sample of the cancer obtained through biopsy or surgery, or sometimes on a blood sample (a “liquid biopsy” that looks for tumour DNA in the bloodstream).

Common biomarker tests include:

• Tests for specific gene mutations (for example, EGFR, KRAS, BRAF, BRCA1/2)
• Tests for gene fusions or rearrangements (for example, ALK, ROS1, NTRK)
• Tests for protein expression on the cancer’s surface (for example, HER2, PD-L1, CD20)
• Broad next-generation sequencing panels that look at many genes at once
• Tests for microsatellite instability (MSI) or mismatch repair status

Major oncology guidelines, including those of NCCN, ASCO, and ESMO, recommend biomarker testing routinely in many cancer types because it directly determines which treatments are likely to work. If the cancer does not carry the relevant target, the matching drug will usually not be effective, and a different approach is chosen.

Types of Targeted Therapy Drugs

Small molecule inhibitors

These are usually taken as tablets or capsules by mouth. They are small enough to enter cells and block signalling proteins inside them. Many of the best-known targeted drugs — for example, those used in CML, EGFR-mutant lung cancer, BRAF-mutant melanoma, and HER2-positive breast cancer — are small molecule inhibitors. The names of many end in “-ib” (such as imatinib, erlotinib, palbociclib).

Monoclonal antibodies

These are larger, protein-based drugs that attach to a specific target on the outside of cancer cells (or on supporting cells like blood vessels). They are usually given as an intravenous infusion or, in some cases, a subcutaneous injection. Their names typically end in “-mab.” Examples include drugs targeting HER2 in breast cancer, CD20 in lymphoma, and VEGF (a blood vessel growth signal) in several cancers.

Antibody-drug conjugates (ADCs)

An ADC links a monoclonal antibody to a potent chemotherapy molecule. The antibody finds the target on cancer cells and delivers the chemotherapy directly inside them. ADCs are now used in HER2-positive breast cancer, certain lymphomas, urothelial cancer, and a growing list of others.

Other classes

• Angiogenesis inhibitors block the growth of new blood vessels that feed tumours.
• PARP inhibitors exploit weaknesses in DNA repair, especially in BRCA-mutated cancers.
• Hormone-based targeted therapies block hormone-driven cancer growth in breast and prostate cancer (some clinicians group these separately from targeted therapy; others include them).
• Proteasome inhibitors, used in multiple myeloma, interfere with how cancer cells break down proteins.

The right class — and the right specific drug — depends entirely on what the tumour testing shows and what is approved or supported by guidelines for that cancer.

The Treatment Plan and What to Expect

Once a targeted therapy has been chosen, your oncology team will discuss the practical details: how the drug is given, how long it is expected to continue, what monitoring is needed, and what side effects to watch for.

How targeted therapy is given

• Oral tablets or capsules taken at home, usually once or twice a day, often continuously. Many small molecule inhibitors fall in this category.
• Intravenous (IV) infusions given in a hospital or day-care oncology unit, often every one to three weeks. Most monoclonal antibodies and antibody-drug conjugates are given this way.
• Subcutaneous injections for a few drugs, given just under the skin.

Duration of treatment

Targeted therapy is often very different from chemotherapy in its rhythm. Chemotherapy is usually given in fixed cycles over a defined period. Targeted therapy, particularly in advanced cancer, is often continued for as long as the cancer is responding and the side effects remain manageable. This may be many months or several years. In some early-stage cancers, targeted drugs are given for a defined period (for example, one year of HER2-directed therapy after breast cancer surgery), as recommended by current guidelines.

Monitoring during treatment

While on targeted therapy, you will have regular reviews. These usually include:

• Clinical consultations to check on symptoms and side effects
• Blood tests to monitor blood counts, liver and kidney function, thyroid function (with certain drugs), and other markers
• Imaging scans (CT, MRI, or PET) every few months to see whether the tumour is shrinking, stable, or growing
• Heart function tests (echocardiogram or similar) for drugs that can affect the heart
• Tumour marker blood tests where relevant

If the cancer progresses on a targeted drug, the team may repeat biomarker testing to look for new mutations that have emerged, and use that information to choose the next line of treatment.

Adherence with oral targeted therapy

When the drug is a tablet you take at home, taking it correctly — the right dose, at the right time, with or without food as instructed — matters a great deal. Missing doses, doubling up, or stopping without medical advice can reduce effectiveness and may increase side effects. Many oral targeted drugs also have important interactions with other medicines, herbal supplements, and even grapefruit. Telling your oncology team about every other medication and supplement is important.

Side Effects and How They Are Managed

Targeted therapy is often described as “gentler” than chemotherapy, but this is only partly accurate. Targeted drugs avoid many classic chemotherapy side effects, such as hair loss and severe drops in blood counts, but they have their own distinct side-effect patterns. Some of these can be serious if not recognised and managed early.

The exact side effects depend on the drug. Your oncology team will give you a specific list for your treatment. The general patterns are below.

Common side effects

• Skin changes, including acne-like rash, dryness, itching, sensitivity to the sun, and changes to nails. These are especially common with EGFR inhibitors.
• Diarrhoea, which can be mild or, with some drugs, more severe.
• Fatigue, often persistent rather than dramatic.
• High blood pressure, particularly with anti-angiogenic drugs.
• Mouth sores and changes in taste.
• Nausea, usually milder than with chemotherapy.
• Hand-foot syndrome (redness, soreness, peeling on palms and soles) with certain drugs.
• Hair thinning rather than full hair loss with many targeted drugs.
• Changes in blood counts, varying by drug.

Less common but serious side effects

• Liver inflammation shown by abnormal blood tests
• Heart problems, including weakened heart pumping or rhythm changes, with specific drug classes
• Lung inflammation (pneumonitis), which can present as new cough or shortness of breath
• Blood clotting problems, including bleeding or clots, with anti-angiogenic drugs
• Wound healing problems, which is why some drugs must be paused around surgery
• Thyroid problems, which is why thyroid function is monitored on some drugs
• Severe skin reactions, which require prompt medical review

How side effects are managed

Most side effects of targeted therapy are predictable and can be managed when they are caught early. The main approaches include:

• Supportive medications, such as anti-diarrhoeal drugs, blood pressure medication, topical treatments for skin reactions, and mouth-care regimens
• Dose reduction, where the drug is continued at a lower dose to make side effects tolerable while preserving benefit
• Temporary treatment breaks to allow side effects to settle before restarting
• Switching to a different drug in the same class if available
• Lifestyle measures, including skincare routines, sun protection, dietary adjustments, and hydration

It is important to report new or worsening symptoms early, even if they seem minor. A rash, a cough that has not gone away, new shortness of breath, swelling in the legs, or a rise in home blood pressure readings can all matter. Most targeted-therapy side effects are easier to manage at the start than after they have become severe.

Response and Monitoring

How well targeted therapy works depends on many factors, including:

• Whether the cancer carries a clear, actionable molecular target
• The cancer type and stage
• What other treatments have been used
• How well the body tolerates the drug
• Whether the cancer develops resistance over time

In cancers driven by a strong, identifiable target — such as CML driven by BCR-ABL, EGFR-mutated lung cancer, HER2-positive breast cancer, BRAF-mutated melanoma, or GIST with KIT mutations — targeted therapy has substantially changed outcomes, with many patients experiencing meaningful tumour shrinkage and long periods of disease control. In other cancers, the benefit is more modest, but still important.

Specific numbers (such as response rates or progression-free survival figures) vary widely by cancer type, drug, and individual situation. Your oncology team can give you realistic estimates based on the published evidence for your particular cancer and the results of your biomarker tests.

The challenge of resistance

One of the most important things to understand about targeted therapy is that cancers can adapt. Over time, cancer cells may develop new mutations that allow them to grow despite the drug. This is called acquired resistance. When it happens, the cancer that had been stable or shrinking may start to grow again.

Resistance is an active area of research. In some cancers, scientists have developed next-generation targeted drugs that work against the common resistance mutations of earlier drugs. Repeating biomarker testing on a new biopsy or a blood sample can help identify what has changed and guide the next step. In other situations, the team may switch to chemotherapy, immunotherapy, or a combination approach.

The possibility of resistance is not a reason to avoid targeted therapy. Many patients benefit for long periods, and even when resistance emerges, the time gained is usually worthwhile and may open up further treatment options.

Combining With Other Treatments

Targeted therapy is rarely the whole story. In most cancers, it is part of a broader plan that may include:

• Surgery to remove the primary tumour where possible. Some targeted drugs are paused around surgery because they affect wound healing or bleeding risk.
• Chemotherapy, either before, alongside, or after targeted therapy depending on the cancer and stage.
• Radiation therapy for local control of the tumour or to treat specific metastatic sites such as the brain or bones.
• Immunotherapy, sometimes given together with targeted drugs and sometimes used sequentially.
• Hormone therapy in breast and prostate cancer, often combined with newer targeted agents.
• Stem cell transplantation in certain blood cancers.

The exact combination and sequence depends on the cancer, its stage, biomarker results, the patient’s overall health, and current guidelines. In many situations, treatment is reviewed by a multidisciplinary team that includes a medical oncologist, surgical oncologist, radiation oncologist, pathologist, radiologist, and other specialists.

Living During Treatment

Because targeted therapy is often long-term, daily life with it is more like managing a chronic condition than recovering from a one-off event. Most people receive treatment as outpatients, take oral medication at home, and continue many normal activities, with adjustments as needed.

Daily routines

If your treatment is a tablet, building a stable daily routine helps with adherence. This might mean linking the dose to a regular meal or to brushing teeth, using pill organisers, or setting a phone alarm. Some drugs need to be taken at consistent times relative to food.

Skin and mouth care

Because skin and mouth side effects are common, a gentle daily routine can help: mild moisturisers, broad-spectrum sun protection, a soft-bristled toothbrush, alcohol-free mouth rinses, and avoiding very hot or spicy foods if mouth sores develop. Your team can recommend specific products for your situation.

Diet and supplements

There is no single “cancer diet” that suits everyone on targeted therapy. The general guidance is to eat a balanced diet, stay well hydrated, and manage specific symptoms (such as diarrhoea or nausea) with practical adjustments. Some targeted drugs interact with grapefruit, certain herbal products, or other medications, so it is important to discuss any supplements with your oncology team before starting them.

Activity, work, and travel

Many people on targeted therapy continue to work, exercise, and travel, particularly when side effects are mild. Fatigue is common, and pacing is often more useful than pushing through. If you plan to travel, your team can advise on timing around infusions, supply of oral medication, and what to do if you become unwell away from home.

Emotional and family support

Long-term cancer treatment carries an emotional load that is sometimes underestimated. Anxiety around scan results (sometimes called “scanxiety”), uncertainty about the future, changes in body image, and the strain on family and caregivers are all common. Counselling, peer support groups, and clear information about what to expect can help. Many oncology teams now include psychologists, social workers, and palliative care specialists who focus on quality of life alongside cancer treatment.

Fertility and contraception

Several targeted drugs can harm a developing fetus, and many are not safe during breastfeeding. If pregnancy is possible, reliable contraception is usually advised during and for some time after treatment. If having children in the future is important, fertility preservation should be discussed before treatment starts wherever possible.

Targeted Therapy in Children

Targeted therapy is also used in childhood cancers, although the range of approved drugs is narrower than in adult oncology. Areas where targeted drugs are part of paediatric care include:

• Certain childhood leukaemias, particularly those with specific genetic changes such as the Philadelphia chromosome
• Some lymphomas
• Neuroblastoma, where targeted antibodies are part of standard high-risk treatment in many countries
• Selected brain tumours, including some low-grade gliomas with BRAF mutations
• Rare tumours with NTRK gene fusions, where dedicated targeted drugs can be effective across many tumour types

Paediatric oncology has some distinct features. Cancers in children often have different driver mutations than adult cancers, so adult biomarker findings do not always translate directly. Drug doses are calculated by body weight or surface area. Side effects on growing tissues — including bones, teeth, heart, and reproductive organs — need particular attention, and long-term follow-up into adulthood is important. Decisions about targeted therapy in children are typically made by specialist paediatric oncology teams, often in the context of clinical trials or international treatment protocols.

For families, the daily care of a child on targeted therapy often falls on parents: giving oral medications correctly, watching for side effects, supporting school attendance where possible, and balancing treatment with the rest of childhood. Paediatric oncology teams usually include nurses, social workers, play therapists, and educators to help with this.

Clinical Trials

Because targeted therapy is one of the fastest-moving areas of cancer treatment, clinical trials are an important option for many patients. Trials may offer access to new drugs that target mutations for which no standard treatment yet exists, or to combinations that are not yet routinely used. They may also be relevant when standard targeted therapy has stopped working.

Trials have careful eligibility criteria, structured monitoring, and clear informed-consent processes. Whether a trial is suitable depends on the cancer, biomarker results, prior treatments, overall health, and what trials are currently open. Discussing trial options with the oncology team early can be worthwhile, even if a standard treatment is also available.

Frequently Asked Questions

Is targeted therapy the same as chemotherapy?

No. Chemotherapy damages any quickly dividing cell. Targeted therapy is aimed at specific molecules or pathways that a particular cancer relies on. Side effects are different, although both can be powerful treatments. The two are sometimes used together.

Is targeted therapy the same as immunotherapy?

No. Immunotherapy changes how the immune system responds to cancer. Targeted therapy acts directly on cancer-cell biology. They are sometimes combined.

Why does my tumour need to be tested before treatment?

Targeted drugs only work if the cancer carries the molecular feature the drug attacks. Biomarker testing identifies which features your specific cancer has, and which drugs match. Without this testing, the wrong drug could be used.

Can I take targeted therapy tablets at home like normal medicine?

Yes, many targeted therapies are oral tablets or capsules taken at home. They are, however, powerful drugs with strict timing, food, and interaction rules. They need to be stored and handled carefully, and missed or doubled doses should be discussed with your team rather than corrected on your own.

How long will I need to stay on targeted therapy?

It depends on the cancer and the situation. In advanced cancer, targeted therapy is often continued as long as it is working and tolerable, sometimes for years. In some early-stage cancers, a defined treatment period is used. Your oncology team will explain what is expected for your case.

What happens if the cancer becomes resistant to my targeted therapy?

Resistance is common over time. When the cancer progresses, options include repeating biomarker testing to look for new mutations, switching to a different targeted drug, adding or switching to chemotherapy or immunotherapy, considering a clinical trial, or using local treatments such as radiation for specific sites of progression.

Are targeted therapies safe long-term?

Many people stay on targeted therapy for years with manageable side effects. Some drugs carry longer-term risks — for the heart, lungs, thyroid, or other organs — which is why monitoring with blood tests and scans continues throughout treatment. Long-term safety also depends on the specific drug and on the individual.

Can I work and travel while on targeted therapy?

Many people do. Fatigue, infusion schedules, and side-effect flares may require adjustments. For oral drugs, you can usually travel with planning. Discuss specific situations — flights, time-zone changes, vaccinations, time off work — with your team.

Do I still need other treatments like surgery or radiation?

Often yes. Targeted therapy is usually part of a broader plan. Surgery, radiation, chemotherapy, immunotherapy, and hormone therapy may all play a role depending on the cancer.

Is targeted therapy available for every cancer?

No. Targeted therapy is available for many cancers, but not all, and only when the cancer carries the right molecular target. For cancers without a clear targetable mutation, other treatments remain the mainstay.

Conclusion

Targeted therapy has changed the picture for many cancers. By aiming at the specific molecules and pathways that drive a tumour’s growth, it offers an approach that is more precise than traditional chemotherapy and, for the right cancers with the right molecular features, can produce strong and sustained responses.

It is also a treatment that asks something of the patient. It depends on careful testing of the tumour, regular monitoring, attention to daily dosing of oral drugs, prompt reporting of side effects, and a willingness to think of cancer care as a long-term partnership with the oncology team. Resistance can develop, side effects need management, and the plan may evolve over time.

If targeted therapy is part of your cancer treatment plan, the most useful conversations to have with your oncologist will be about what your specific biomarker results mean, which drug or combination is being recommended for your cancer, what side effects to watch for, how progress will be measured, and what the options are if the cancer changes its behaviour over time. Those answers will be specific to your cancer, your testing, and your circumstances — and they are the foundation of treatment decisions made well.