What is Radiation Therapy?

Radiation therapy (or radiotherapy) is a form of cancer treatment that damages or kills cancer cells by ionizing radiation, high-energy particles or waves, usually X-rays. Radiation works through direct and indirect damage to the genes that control cancer cells’ growth and division.

The goal of radiotherapy is to limit the spread of cancer cells while minimizing harm to nearby healthy tissue. It can be used to shrink tumors, reduce pressure, and treat other symptoms of cancer.

About 4 out of 10 patients with cancer receive some type of radiation therapy in their prescribed treatment plan. This can be an effective treatment by itself, but other types of cancer are best treated through a combination of procedures, which may include surgery, chemotherapy and immunotherapy.

Radiotherapy can be administered in a number of ways, from external machines, to the insertion of radioactive material. Refer below for the list of radiation therapy treatment techniques commonly used in Asian Alliance Radiation & Oncology.

This technique uses 3-dimensional scans to determine the exact shape and size of the tumour. The radiation beams are shaped by tiny leaves (multi-leaf collimator) that are arranged to fit the tumour shape, minimising the side effects to health tissue. Click here to find out more.

Brachytherapy, or internal radiation therapy, refers to the placement of a radiation source close to or into the tumour through the insertion of applicators into the body. Brachytherapy is used to treat cancer sites such as cervix, uterus, vagina, prostate, breast, and skin cancers. Click here to find out more.

Image-guided radiation therapy (IGRT) is the use of imaging during radiation therapy to improve the precision and accuracy of treatment delivery. IGRT is used to treat tumors in areas of the body that move, such as the lungs and liver. Radiation therapy machines are equipped with imaging technology to allow your doctor to image the tumour before and during treatment. By comparing these images to the reference images taken during simulation, the patient’s position may be adjusted to more precisely target the radiation dose to the tumour. Click here to find out more.

Intensity modulated Radiation Therapy (IMRT) is a type of conformal radiation, which shapes radiation beams to closely approximate the shape of the tumor. The intensity of the radiation in IMRT can be changed during treatment to spare more adjoining normal tissue than is spared during conventional radiation therapy. Because of this an increased dose of radiation can be delivered to the tumor using IMRT. Click here to find out more.

Stereotactic Body Radiation Therapy (SBRT) is a radiation therapy approach which delivers high dose radiation to a target within the body, usually up to five treatment sessions. It is able to determine the beam direction and intensity using the treatment-planning software, accounting for tumour motion and anatomy changes during the treatment procedure. Click here to find out more.

Stereotactic Radiosurgery (SRS) is a type of radiotherapy that allows precise and high dose radiation beams to be delivered to a small, localised area of the body, mostly in the brain to destroy a lesion with a single radiation dose. Click here to find out more.

Side Effects of Radiation Therapy

There are common side effects associated with undergoing Radiation Therapy treatment. For more information on Radiation Therapy side effects, click here.

Our Cancer Specialists


Dr. Jonathan Teh Yi Hui

Medical Director (CSR) & Senior Consultant Radiation Oncologist

Stereotactic Radiosurgery (SRS/SBRT), Head & Neck, Pediatric, Urologic, Gastrointestinal Cancers & Sarcoma


Dr Daniel Tan Yat Harn

Director & Senior Consultant Radiation Oncologist

Stereotactic Radiosurgery (SRS/SBRT), Brain and Spine, Breast and Prostate Cancers


Dr David Tan Boon Harn

Medical Director (AARO) & Senior Consultant Radiation Oncologist

Stereotactic Radiosurgery (SRS/SBRT), Gynaecological, Gastrointestinal & Lung Cancers


Dr Michelle Tseng Shu Fen

Women's & Children Program Director & Consultant Radiation Oncologist

Women’s & Children’s Cancer, Breast and Gynae-oncology and Paediatric