Understanding Chemotherapy vs Radiation Therapy at the National Cancer Centre Singapore

Chemotherapy and radiation therapy are two of the most widely used cancer treatments. Although both aim to control or eliminate cancer, they work in different ways and are used for different purposes. At the National Cancer Centre Singapore (NCCS), specialists evaluate each patient’s condition carefully to determine the most suitable treatment approach, whether chemotherapy, radiation therapy or a combination of both. This page provides an overview of how each treatment works, when they are used and what patients can expect throughout their care.

What Chemotherapy and Radiation Therapy Aim to Do

Cancer treatments are selected based on the type of cancer, the stage of the disease and the goals of care. While chemotherapy and radiation therapy may be used on their own, they often form part of a broader treatment plan designed to achieve the best possible outcome for patients, such as to:

• Treat cancer by destroying or damaging cancer cells 
• Control the disease by slowing its growth or preventing spread 
• Support other treatments, such as shrinking a tumour before surgery 
• Reduce symptoms and improve quality of life 
• Lower the risk of recurrence after primary treatment

Understanding the difference between chemotherapy and radiation therapy helps patients make sense of why certain treatments are chosen and how they fit into the overall management plan.

What Is Chemotherapy

Chemotherapy is a type of treatment that uses anti-cancer drugs to kill cancer cells. It stops cancer cells from growing and reproducing.

Chemotherapy drugs can be given orally (by mouth) or by injection where the drugs enter the blood stream to be distributed throughout the body to kill cancer cells.

Your treating doctor will tailor the type of chemotherapy and dosage based on your cancer type, stage of the disease, overall health, goals and preferences.

Intravenous chemotherapy

This is the most common method. The medicine is delivered directly into the bloodstream through a drip or injection, allowing it to reach cancer cells throughout the body quickly and effectively.

Oral chemotherapy

Some chemotherapy medicines are available as pills or capsules. The pharmacist will tell you how and when to take them, and how to handle the drugs safely.

Subcutaneous or intramuscular injections

In certain cases, chemotherapy may be injected under the skin or into a muscle. This is used for medicines that do not require full intravenous infusion but still need to enter the bloodstream. Intraperitoneal chemotherapy This approach delivers the chemo drugs directly into the peritoneal cavity, the area in the body that contains organs such as intestines, stomach and liver.

What Is Radiation Therapy

Radiation therapy (RT) or radiotherapy is the use of ionising radiation to treat patients with cancer and certain non-cancerous conditions. It works by damaging the DNA of cells and affecting their ability to multiply. Although radiation affects all cells, cancer cells are generally more sensitive to radiation damage. Each patient’s radiation treatment is carefully planned to minimise the radiation dose to nearby organs and healthy tissues.

Your treating doctor will tailor the type of radiation therapy based on your cancer type, stage of the disease, overall health, goals and preferences.

Radiation therapy may be recommended to:

• Treat localised cancers 
• Reduce the chance of cancer returning after surgery 
• Manage symptoms such as pain, bleeding or pressure 
• Treat tumours in areas where surgery is not suitable

Advances in radiation therapy technology allow specialists to map the tumour precisely, improving accuracy while protecting surrounding healthy tissues. Modern techniques enhance both the effectiveness and safety of treatment.

Intensity-Modulated Radiation Therapy (IMRT)

This is a form of 3D conformal radiation therapy that focuses multiple radiation beams onto the tumour. The beam intensities can be varied, so that the highest possible dose can be used to destroy cancerous tissue while sparing normal structures.

Image-Guided Radiation Therapy (IGRT)

IGRT uses imaging technologies to locate a tumour target before radiation therapy treatment. This process aims to improve treatment accuracy by reducing the need for large target margins. This minimises the amount of healthy tissue exposed to radiation and reduces side effects.

Volumetric Modulated Arc Therapy (VMAT)

VMAT refers to the delivery of IMRT in a volumetric arc fashion. Treatment is delivered as the machine rotates 360 degrees around the patient through one or more arcs delivering radiation. The shape of the beam varies as the machine rotates to achieve a complex high dose volume in 3D to encompass the tumour.

Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT)

This system of delivering radiation therapy combines the advantages of radiosurgery and IMRT with an image tracking guidance system to further enhance treatment accuracy.

Proton Therapy

An advanced type of radiation treatment, proton therapy targets cancer cells using positively charged subatomic particles called protons. The unique physical properties of protons enable tumours to be more precisely targeted compared to the x-rays used in conventional radiation therapy. This minimises damage to nearby healthy tissues and organs and therefore results in fewer treatment-related side effects. It is most beneficial for patients who have cancers in sensitive areas like the head or neck and paediatric cancers.

NCCS is the only public healthcare institution in Singapore to offer proton therapy at the Goh Cheng Liang Proton Therapy Centre. For more information on proton therapy, click here.

Chemotherapy vs Radiation Therapy: Key Differences

Although both treatments aim to control cancer, they differ in how they work, how they are given and the situations in which they are used.

How they work

Chemotherapy affects the entire body by circulating through the bloodstream, making it suitable for cancers that have spread. Radiation therapy targets a specific area, making it effective for localised tumours.

How they are delivered

Chemotherapy is given as systemic medication (oral or intravenous). Radiation therapy is delivered through precisely directed beams or implanted radioactive sources.

Treatment goals

Both may aim to cure, control or relieve symptoms. The choice depends on the cancer type, stage and overall treatment strategy.

Your NCCS team will explain why a particular treatment or combination is recommended and how each option contributes to the overall plan.

When Are Chemotherapy and Radiation Therapy Used Together

In some situations, chemotherapy and radiation therapy are used at the same time. This is known as chemoradiation. Chemotherapy enhances the effect of radiation therapy by making cancer cells more sensitive to radiation.

Chemoradiation may be used for localised cancers where tumours are extensive, deep or inoperable.

While this approach can be highly effective, it may also increase the likelihood of side effects, and patients are monitored closely throughout treatment.

What Patients Can Expect During Treatment

Throughout chemotherapy or radiation therapy, patients undergo regular reviews to assess progress, monitor for side effects and adjust treatment if needed. These reviews may include imaging tests, blood tests and physical examinations. Alongside the medical aspects of care, patients may also receive guidance on nutrition, rehabilitation and emotional wellbeing to support their overall health.

Side effects may vary depending on whether chemotherapy or radiation therapy is used. Chemotherapy travels throughout the body, so its effects are often systemic and may involve changes in blood counts, digestion, energy levels or hair growth. Radiation therapy targets a specific area, and its side effects tend to be localised to the region being treated, such as skin changes, irritation or temporary discomfort in nearby organs. Some reactions, such as fatigue, may occur with either treatment.

Early communication with the care team helps address concerns and supports a smoother treatment experience.

Support at NCCS

NCCS provides comprehensive support for patients receiving chemotherapy, radiation therapy or both. Depending on individual needs, support may include symptom management, nutritional advice, rehabilitation services and psychological support. Long-term follow-up is also provided to monitor recovery, detect potential late effects and guide patients through survivorship.

Patients are encouraged to take an active role in their care. Education and clear guidance help them recognise symptoms early, understand when to seek help and make informed decisions throughout treatment and recovery.

Guidance and Support

Understanding chemotherapy vs radiation therapy helps patients feel more prepared as they begin treatment. At NCCS, specialists are committed to providing clear explanations, personalised recommendations and ongoing care. Your team will discuss the most suitable treatment options, what to expect and how to manage your health throughout your cancer journey.

For more information, please speak with your NCCS care team or visit www.nccs.com.sg.