Radiotherapy

What it is

Radiotherapy, also called radiation therapy or radiation treatment, is a cancer treatment that uses high-energy radiation to damage cancer cells, and more than half of people with cancer receive it at some point during care. It is used to cure some cancers, lower the chance of cancer coming back, shrink tumours before surgery, or relieve symptoms such as pain, bleeding, or pressure in advanced disease. The radiation most often used is high-energy X-rays, but treatment can also use electrons, gamma rays, or protons.

Radiotherapy is usually a local treatment, meaning it targets a specific part of the body rather than the whole body. The main aim is to deliver enough dose to the tumour while limiting dose to nearby normal tissues. Modern planning uses imaging and computer-based dose calculations to shape treatment precisely.

Common forms include:

Type	What it means	Typical use
External beam radiotherapy (EBRT)	Radiation is delivered from a machine outside the body	Most common form for many cancers
Brachytherapy	A radioactive source is placed in or near the tumour	Cervix, prostate, some head and neck and gynecologic cancers
Systemic radiotherapy	A radioactive medicine is swallowed or injected	Selected cancers such as thyroid cancer or some metastatic disease
Proton therapy	Uses protons instead of X-rays	Selected cases where dose sparing is especially important

In India, radiotherapy is a core part of cancer treatment in tertiary cancer centres and many regional oncology units, though access to advanced techniques can vary by city and hospital.

How it works

Radiotherapy works mainly by damaging the DNA inside cells. Cancer cells are generally less able than normal cells to repair this damage, so they are more likely to stop dividing and die. Normal tissues can also be affected, which is why treatment is carefully planned and divided into sessions called fractions.

Fractionation is important because giving the total dose over several treatments allows normal tissues time to repair between sessions while still injuring tumour cells. Some cancers are treated with many small daily fractions over several weeks, while others can be treated with shorter courses or a few larger fractions, depending on the cancer type, location, and treatment goal.

Modern radiotherapy often includes techniques such as:

1. 3D conformal radiotherapy (3D-CRT): shapes beams to the tumour.
2. Intensity-modulated radiotherapy (IMRT): varies beam intensity to better spare normal tissue.
3. Image-guided radiotherapy (IGRT): uses imaging during treatment to improve accuracy.
4. Stereotactic radiotherapy/radiosurgery (SBRT/SRS): gives very precise, high-dose treatment in a small number of sessions.

These methods help reduce dose to organs at risk, but they do not remove side effects completely.

Evidence and uses

Radiotherapy is used in the treatment of many cancers, including breast, cervix, head and neck, prostate, lung, brain, rectal, and skin cancers, as well as lymphomas and some childhood cancers. It may be used alone or combined with surgery, chemotherapy, targeted therapy, immunotherapy, or hormone therapy.

Common treatment settings include:

• Definitive treatment: used as the main treatment to try to cure cancer.
• Neoadjuvant treatment: given before surgery to shrink a tumour.
• Adjuvant treatment: given after surgery to lower recurrence risk.
• Concurrent chemoradiation: given with chemotherapy to improve tumour control in selected cancers.
• Palliative radiotherapy: used to relieve symptoms such as bone pain, bleeding, swallowing difficulty, or pressure on nerves.

Evidence from decades of clinical trials shows that radiotherapy improves local control and, in many cancers, survival. Technological advances have made treatment more precise, with better targeting and lower exposure to surrounding tissues than older methods. Still, benefit depends on the cancer type, stage, exact location, and the person's overall health.

Radiotherapy is not the right choice for every patient or every tumour. Some cancers are more sensitive to radiation than others. In some situations, surgery or systemic therapy may be preferred, and in others radiotherapy is part of combined treatment.

Safety and interactions

Radiotherapy is not a medicine you swallow, but it still has important safety issues. Side effects depend strongly on the body part treated, total dose, dose per fraction, and whether chemotherapy or other drugs are given at the same time.

Common short-term side effects can include:

• Fatigue
• Skin redness, dryness, or peeling in the treated area
• Sore mouth or throat for head and neck treatment
• Difficulty swallowing
• Nausea or diarrhoea for abdominal or pelvic treatment
• Hair loss only in the treated area
• Urinary or bowel irritation for pelvic treatment

Possible long-term effects vary by site and may include fibrosis, dry mouth, bowel or bladder changes, infertility, lymphedema, nerve injury, or rarely a second cancer years later. These risks are usually weighed against the expected benefit of treatment.

Radiotherapy can interact with other cancer treatments. Chemotherapy, targeted drugs, and immunotherapy may increase both effectiveness and side effects when given together. Some medicines can worsen skin reactions or affect healing. Patients should tell the radiation oncology team about all prescription drugs, over-the-counter medicines, supplements, and herbal products. If you are pregnant or might be pregnant, this must be discussed before treatment because radiation can harm a fetus.

External beam radiotherapy does not make most patients radioactive after a session. With brachytherapy or systemic radioactive treatments, temporary radiation precautions may be needed, depending on the method used.

When to see a clinician

A radiation oncologist should assess whether radiotherapy is appropriate if a cancer has been diagnosed, if symptoms from cancer need relief, or if surgery alone may not be enough. During treatment, contact the care team promptly for fever, severe pain, inability to eat or drink, uncontrolled vomiting or diarrhoea, worsening breathlessness, heavy bleeding, confusion, or skin breakdown in the treated area.

It is also reasonable to ask practical questions before treatment starts, such as the goal of treatment, number of sessions, expected side effects, fertility implications, work and travel restrictions, and whether supportive care such as nutrition, dental review, or speech and swallowing therapy is needed. In India, patients may also need guidance on where treatment planning, simulation, and daily sessions will be done, because these may require repeated visits over days to weeks.

Limitations and open questions

Radiotherapy is highly effective, but it has limits. Some tumours are resistant, some are too close to critical organs for full-dose treatment, and microscopic spread elsewhere in the body usually requires systemic treatment rather than local radiation alone. Access to advanced technologies such as IMRT, SBRT, and proton therapy is uneven across regions and can affect convenience, cost, and treatment options.

Research continues on better imaging, adaptive radiotherapy, particle therapy, biomarkers that predict radiation response, and safer combinations with immunotherapy and targeted drugs. Evidence is strong for radiotherapy overall, but the advantage of newer technologies over standard approaches can vary by cancer type and outcome measured. For patients, the key question is not whether a technique is newer, but whether it is likely to improve tumour control, reduce side effects, or both in their specific case.