Dr. Deenadayalan T on how cancer treatment has changed in 25 years (Tamil).
Modern cancer treatment is no longer chosen only by where the tumour sits. It is chosen by what is driving it. Genetic and molecular testing of the tumour now identifies the specific mutation fuelling its growth, and treatment — targeted therapy, immunotherapy, or chemotherapy — is matched to that mutation. This approach is called precision oncology.
Twenty-five years ago, an oncologist had three tools: surgery, radiation and chemotherapy. Two patients with the same tumour in the same organ got broadly the same treatment. Today those two patients may receive entirely different drugs, because their tumours turn out to be different diseases at the genetic level.
What is precision oncology?
Precision oncology is the practice of selecting cancer treatment based on the genetic and molecular profile of a patient’s tumour rather than its anatomical location alone. Instead of asking only “where is the cancer?”, the oncologist also asks “what mutation is driving this cancer?” — and prescribes a drug designed to block that specific mechanism.
The practical consequence is significant. A lung cancer with an EGFR mutation and a lung cancer without one are treated differently. A breast cancer that is HER2-positive and one that is triple-negative are treated differently. Same organ. Different disease. Different drug.
Cancer treatment: then and now
| 25 years ago | Today | |
| Treatment chosen by | Organ and stage | Organ, stage, genetics, biomarkers |
| Main options | Surgery, radiation, chemotherapy | Plus targeted therapy, immunotherapy, hormone therapy |
| Diagnostics | Microscope, basic staining | Immunohistochemistry, NGS, biomarker panels |
| Delivery | Long inpatient admissions | Oral tablets, short day-care infusions |
| Side-effect profile | Broad — healthy cells hit alongside cancer | Narrower, but with new toxicities of its own |
| Advanced disease | Often rapidly fatal | Often a manageable long-term condition |
What made this possible: NGS and the Cancer Genome Atlas
Two developments turned precision oncology from theory into daily practice.
Next-Generation Sequencing (NGS)
Next-Generation Sequencing is a laboratory test that reads the DNA of a tumour and identifies the mutations driving it. A single NGS panel can screen hundreds of genes at once and report actionable targets, resistance mutations, tumour mutational burden and other biomarkers that determine which drugs will work.
Sequencing the first human genome took over a decade and cost billions of dollars. The same work now takes days and costs a fraction of that. That collapse in cost is what put genomic testing within reach of an ordinary patient in an ordinary clinic.
The Cancer Genome Atlas (TCGA)
The Cancer Genome Atlas was a landmark research programme, run by the US National Cancer Institute and National Human Genome Research Institute, that molecularly characterised more than 20,000 primary tumours across 33 cancer types. Its central finding reshaped oncology: cancers that look identical under a microscope are often genetically distinct diseases requiring different treatment.
Targeted therapy explained
Targeted therapy is a class of cancer drug that blocks a specific protein or molecular pathway the cancer depends on to grow. Conventional chemotherapy attacks all rapidly dividing cells, which is why it damages hair follicles, bone marrow and the gut lining. Targeted therapy attacks a mechanism that is largely unique to the cancer cell, so it spares far more healthy tissue.
Three drugs that changed oncology
| Drug | Target | Used in |
| Imatinib | BCR-ABL fusion protein | Chronic Myeloid Leukaemia (CML) |
| Trastuzumab | HER2 receptor | HER2-positive breast and gastric cancer |
| Rituximab | CD20 protein on B-cells | Non-Hodgkin Lymphoma (NHL) |
Imatinib is the clearest illustration of what precision medicine achieved. Before it, chronic myeloid leukaemia was a fatal disease with a median survival measured in a few years. With imatinib — a daily tablet — most patients now have a life expectancy approaching that of the general population. One drug, one target, one disease transformed.
Immunotherapy explained
Immunotherapy does not attack the cancer directly. It removes the brakes the cancer has placed on your own immune system, so your T-cells can recognise and destroy the tumour themselves. Cancers survive partly by switching off the immune response against them; checkpoint inhibitors switch it back on.
The impact has been most dramatic in cancers that were previously close to untreatable at an advanced stage — metastatic melanoma, some lung cancers, kidney and bladder cancers. A subset of these patients now achieve durable, long-lasting remissions. The discovery of immune checkpoint therapy was recognised with the 2018 Nobel Prize in Physiology or Medicine.
An honest caveat: immunotherapy does not work for everyone, and it carries its own risks. Because it activates the immune system, it can cause immune-related side effects affecting the thyroid, lungs, liver, skin or bowel. Biomarker testing (such as PD-L1 expression) helps identify who is most likely to benefit.
Chemotherapy vs targeted therapy vs immunotherapy
| Chemotherapy | Targeted therapy | Immunotherapy | |
| How it works | Kills rapidly dividing cells | Blocks a specific cancer protein or pathway | Activates the patient’s own immune system |
| Selects patients by | Cancer type and stage | Presence of a specific mutation | Biomarkers such as PD-L1, MSI, TMB |
| Typical delivery | IV infusion cycles | Often a daily oral tablet | IV infusion every 2–6 weeks |
| Common side effects | Hair loss, nausea, low blood counts, infection risk | Rash, diarrhoea, fatigue; drug-specific toxicities | Immune-related inflammation of thyroid, lung, liver, bowel |
| Still essential? | Yes — remains the backbone of many regimens | Only when a matching target is present | Only when biomarkers predict benefit |
These are not competing options where one is simply “better”. They are different tools. Many patients receive a combination — for example, chemotherapy plus immunotherapy, or surgery followed by targeted therapy.
What this means for a patient in practice
The change patients notice most is not the science. It is the logistics.
- Many treatments are now tablets taken at home rather than week-long hospital admissions.
- Day-care infusions mean patients come in, receive treatment, and go home the same day.
- Many patients continue working through treatment.
- Advanced cancer is increasingly a chronic condition — controlled over years rather than measured in months.
None of this is possible without an accurate diagnosis first. Genomic testing requires tumour tissue, which means a biopsy is the gateway to every one of these treatments. Delaying the biopsy delays access to precision medicine.
Frequently asked questions
Is chemotherapy outdated?
No. Chemotherapy remains a cornerstone of cancer treatment and cures several cancers outright, including testicular cancer, many lymphomas and childhood leukaemias. It is now used more precisely, often alongside targeted therapy or immunotherapy — not replaced by them.
Is targeted therapy better than chemotherapy?
Not automatically. Targeted therapy only works if the tumour carries the specific target the drug is designed to block. If your tumour has no actionable mutation, targeted therapy will do nothing, and chemotherapy may be the more effective choice. The right answer depends entirely on your tumour’s biology.
Does every cancer patient need genetic testing?
No. Molecular testing is standard for some cancers — such as lung, colorectal, breast and ovarian — where the results directly change treatment. For others, it may add cost without changing the plan. Your oncologist should be able to explain exactly what decision the test would inform.
Are these treatments available in India?
Yes. Targeted therapy, immunotherapy and NGS testing are all available in India, and several targeted drugs now have Indian generic or biosimilar versions at substantially lower cost than the originators. Availability and affordability still vary, and cost should be discussed openly with your oncologist before treatment begins.
Can advanced cancer really be controlled long-term?
For a growing number of cancers, yes. Patients with advanced disease driven by an actionable mutation, or responsive to immunotherapy, can live for years with good quality of life. This is not true for every cancer or every patient, and no honest oncologist will promise it — but it is now a realistic outcome where it was not two decades ago.
Key takeaway
Cancer treatment has moved from one-size-fits-all to one-patient-at-a-time. The tumour is sequenced, the driver mutation is identified, and the drug is matched to it. The goal of modern oncology is simple to state and hard to achieve: the right treatment, for the right patient, at the right time.
Consult a medical oncologist in Madurai
Dr. Deenadayalan T is a Consultant Medical Oncologist in Madurai practising precision oncology, targeted therapy, immunotherapy, chemotherapy and personalised cancer treatment. For a treatment plan or a second opinion on an existing one, you can book a consultation below.
Sources
- National Cancer Institute — The Cancer Genome Atlas Program (TCGA)
- National Cancer Institute — Targeted therapy to treat cancer
- National Cancer Institute — Immunotherapy to treat cancer
Medically reviewed by Dr. Deenadayalan T, MD, DM (Medical Oncology). Last reviewed: 15 July 2026. This article is for general information only and is not a substitute for professional medical advice, diagnosis or treatment. Treatment decisions must be made with your treating oncologist.