Is targeted therapy the same as chemotherapy?

No. Chemotherapy generally attacks rapidly dividing cells, while targeted therapy is designed to block a specific molecule or pathway that the cancer depends on. Some targeted drugs are tablets taken daily, and some are IV infusions. In practice, doctors may use targeted therapy alone or combine it with chemotherapy depending on the cancer type and stage.

How do doctors know if targeted therapy will work for my cancer?

Doctors usually need biomarker testing to look for a matching target such as HER2 amplification, an EGFR mutation, an ALK fusion, or a BRCA-related DNA repair defect. The test may be done on tumour tissue using IHC, FISH, PCR, or next-generation sequencing, and sometimes on blood through a liquid biopsy. If the target is absent, the drug is often much less likely to help.

Does targeted therapy have fewer side effects than chemotherapy?

Sometimes, but not always. Targeted therapy is often more selective than chemotherapy, yet it can still cause serious problems such as rash, diarrhoea, high blood pressure, liver injury, heart dysfunction, bleeding, or lung inflammation depending on the drug. Because many agents are taken for weeks to months, regular blood tests, scans, blood pressure checks, or heart monitoring may be needed.

Can targeted therapy stop working over time?

Yes. This is called resistance, and it can happen after an initial good response. Cancer cells may develop a new mutation, activate another signalling pathway, or change enough that the original drug no longer controls them. When this happens, oncologists may repeat a biopsy, order liquid biopsy testing, or switch to a next-generation targeted drug or another treatment type.

Is targeted therapy available in India?

Yes, many targeted therapies and the tests needed to guide them are available in India, especially in tertiary cancer centres and larger private or academic hospitals. Availability varies by city, cancer type, and cost, and some patients may need to send samples to specialised molecular laboratories. If targeted therapy is being considered, ask whether your tumour should be tested and whether a generic, biosimilar, or assistance programme is available.

Targeted therapy — Glossary | India Cancer Guide

What it is

Targeted therapy is cancer treatment that acts on specific molecular targets, with imatinib's 2001 approval marking a major milestone. In plain language, these medicines are designed to block a gene, protein, receptor, or signalling pathway that helps cancer cells grow, survive, spread, or make new blood vessels. The most important practical fact is that targeted therapy usually works best only when the tumour has the matching target, so biomarker testing is often needed before treatment starts.

Targeted therapy is a treatment modality, not a single drug. It includes oral small-molecule drugs and intravenous monoclonal antibodies. Compared with traditional cytotoxic chemotherapy, targeted therapy is usually more selective, but it is not side-effect free and it is not automatically better for every cancer.

Common examples include drugs aimed at EGFR, HER2, ALK, BCR-ABL, VEGF/VEGFR, PARP, CDK4/6, BTK, FGFR, MET, KRAS G12C, and NTRK fusions. In India, access increasingly depends on pathology and molecular testing such as immunohistochemistry, FISH, PCR, or next-generation sequencing, which may be done in larger cancer centres and reference laboratories.

Main form	How it is given	Typical target example
Small-molecule inhibitor	Usually oral tablets/capsules	EGFR, ALK, BCR-ABL, PARP, CDK4/6
Monoclonal antibody	Intravenous infusion	HER2, EGFR, VEGF

How it works

Cancer cells often depend on abnormal molecular signals called driver alterations. These may be mutations, gene fusions, amplifications, or overexpressed receptors. Targeted therapy tries to interrupt those signals.

A few common mechanisms are:

Blocking growth signals at the cell surface. Antibodies can bind receptors such as HER2 or EGFR and stop activation.
Inhibiting enzymes inside the cell. Tyrosine kinase inhibitors can block signalling pathways that tell cancer cells to divide.
Cutting off tumour blood supply. Some drugs target VEGF or VEGFR and reduce angiogenesis.
Exploiting DNA repair weakness. PARP inhibitors are used in cancers with defects in homologous recombination, including some BRCA-related cancers.
Slowing the cell cycle. CDK4/6 inhibitors reduce cell division in selected breast cancers.

This is why targeted therapy is closely linked to precision oncology. The same cancer organ site can contain very different molecular subtypes. For example, lung cancer may be driven by EGFR mutations, ALK rearrangements, KRAS mutations, MET alterations, or other changes, and the treatment choice can differ accordingly.

Evidence and uses

Targeted therapy has changed outcomes in several cancers, but benefit depends on choosing the right drug for the right target. One classic example is imatinib for chronic myeloid leukaemia with the BCR-ABL fusion, which helped establish the modern model of molecularly matched treatment.

Examples of where targeted therapy is commonly used include:

Breast cancer: HER2-targeted drugs such as trastuzumab for HER2-positive disease; CDK4/6 inhibitors for many hormone receptor-positive advanced cancers.
Non-small cell lung cancer: EGFR, ALK, ROS1, MET, RET, KRAS G12C, and NTRK-directed therapies in selected patients.
Colorectal cancer: EGFR antibodies in selected RAS wild-type tumours.
Ovarian, breast, prostate, pancreatic cancers: PARP inhibitors in selected biomarker-defined settings.
Leukaemias and lymphomas: BCR-ABL inhibitors, BTK inhibitors, PI3K inhibitors, and others in specific diseases.
GIST and kidney cancer: multi-kinase inhibitors and other targeted agents.

Targeted therapy may be used alone or with chemotherapy, endocrine therapy, radiation, or immunotherapy. In some cancers it is used in early-stage treatment; in others it is mainly used for advanced or metastatic disease.

It is important to separate targeted therapy from immunotherapy. Some articles discuss them together under systemic therapy, but in routine oncology they are usually treated as different categories. A drug can still have immune-related effects indirectly, and combinations are being studied and used in some settings.

Targeted therapy is often described as less toxic than chemotherapy, and that can be true in some situations, but the comparison is incomplete. These drugs can cause serious toxicities of their own, and some require close monitoring for heart, liver, lung, skin, blood pressure, eye, or blood count problems.

Safety and interactions

Side effects depend on the drug and target. Common patterns include:

Drug group/example	Common or important risks
EGFR inhibitors	Acne-like rash, diarrhoea, nail and skin changes, rare lung inflammation
HER2-targeted therapy	Infusion reactions, diarrhoea with some agents, possible heart dysfunction
VEGF/VEGFR inhibitors	High blood pressure, bleeding, clotting, poor wound healing, proteinuria
ALK/other TKIs	Liver test abnormalities, swelling, diarrhoea, fatigue, rhythm effects with some drugs
PARP inhibitors	Nausea, fatigue, anaemia and other low blood counts
CDK4/6 inhibitors	Neutropenia, diarrhoea, liver abnormalities, QT prolongation with some drugs
BTK inhibitors	Bleeding, atrial fibrillation, infections, diarrhoea

Drug interactions matter because many targeted therapies are taken by mouth and are metabolised through liver enzymes such as CYP3A4. Other prescription drugs, antifungals, antibiotics, anti-seizure medicines, acid-suppressing drugs, and some supplements can change drug levels. Grapefruit and grapefruit juice can interact with certain agents. Patients should tell their oncologist and pharmacist about all medicines, including Ayurvedic products, herbal supplements, and over-the-counter tablets.

Do not start, stop, crush, split, or combine a targeted therapy without oncology advice. If you miss doses, have severe diarrhoea, fever, new breathlessness, chest pain, uncontrolled blood pressure, unusual bleeding, or a widespread rash, contact your treatment team promptly.

Diagnosis / how it's measured

Targeted therapy is usually chosen after finding a relevant biomarker in the tumour or blood. Tests may include:

Immunohistochemistry (IHC) for protein expression, such as HER2.
FISH for gene amplification or rearrangement.
PCR-based tests for specific mutations.
Next-generation sequencing (NGS) panels for multiple genes at once.
Liquid biopsy in some settings, especially when tissue is limited or resistance is suspected.

The exact test depends on the cancer type. For example, HER2 testing is standard in breast cancer, while broad molecular profiling is increasingly used in advanced lung cancer. In India, testing availability and cost vary by centre, and patients sometimes need referral to a tertiary cancer hospital or accredited molecular lab.

A tumour can also change over time. If cancer grows after an initial response, doctors may repeat a biopsy or use liquid biopsy to look for a resistance mutation, such as EGFR T790M in some lung cancers.

When to see a clinician

Ask your oncologist about targeted therapy if you have a new cancer diagnosis, recurrent cancer, or cancer that has stopped responding to treatment. It is especially relevant when guidelines recommend biomarker testing for that cancer type.

Seek urgent medical advice during treatment if you develop:

fever or signs of infection
sudden shortness of breath or new cough
chest pain or palpitations
severe diarrhoea or vomiting
heavy bleeding or black stools
severe headache or very high blood pressure
yellowing of the eyes, dark urine, or marked fatigue

Limitations and open questions

Targeted therapy is not a universal solution. Many cancers do not have an actionable target, and even when a target is present, the response may be partial or temporary. Resistance is a major limitation: cancer cells can acquire new mutations, activate bypass pathways, or become less dependent on the original target.

Another limitation is tumour heterogeneity. Different parts of the same cancer, or different metastases, may not carry exactly the same molecular changes. This can make treatment response uneven.

Evidence is strong for some matched drug-target pairs, but weaker or still emerging for others, especially rare mutations and off-label use. Access, cost, and testing quality also affect real-world benefit. Ongoing research is focused on better biomarker selection, combination strategies, treatment after resistance, and ways to make precision oncology more available in routine care.

Targeted therapy