Radiation Therapy — Using Targeted Rays to Treat Cancer

Radiation therapy is a localised clinical treatment modality that delivers ionising radiation, such as high-energy X-rays, gamma rays, protons, or electrons, to targeted tissues. The radiation works by inducing single- and double-strand breaks in the DNA of cells within the target area. Because cancer cells typically exhibit defective DNA repair pathways compared to normal cells, they are unable to replicate and undergo apoptotic or mitotic cell death.

Radiotherapy can be administered externally or internally. External beam radiation therapy (EBRT) utilises linear accelerators to direct precise beams into the body from multiple angles. Internal radiation, or brachytherapy, involves placing sealed radioactive capsules or seeds directly into or adjacent to the tumour mass. Radiotherapy is tailored via advanced imaging to conform closely to tumour geometry.

Roughly half of all cancer patients receive radiation therapy at some stage during their illness. It serves critical roles: it can eliminate early-stage tumours entirely, shrink tumours before surgery, destroy residual cancer cells after an operation, or control symptoms such as bone pain and bleeding in advanced disease. Understanding radiotherapy helps patients prepare for daily treatment schedules, actively manage expected side effects, and engage confidently with their care plans.

Radiotherapy does not rely on a standalone blood test for delivery; rather, treatment planning requires high-resolution imaging, such as CT simulation, MRI, and PET scans, to accurately map target volumes. Tumour biopsies provide histological confirmation and molecular details, such as HPV status in oropharyngeal cancer or microsatellite stability, which help determine radiation sensitivity and fractionation schedules.

Radiation therapy is utilised across almost all cancer types. It is central to treating breast, lung, prostate, and head and neck cancers, where it can provide definitive curative treatment or post-operative risk reduction. It is also used in brain tumours, gynaecological malignancies like cervical and endometrial cancer, gastrointestinal cancers, lymphomas, and soft tissue sarcomas.

Radiotherapy is frequently combined with other treatments to maximise therapeutic benefit. It may be administered alongside concurrent chemotherapy as a radiosensitiser, used preoperatively (neoadjuvantly) to downstage tumours, or postoperatively (adjuvantly) to clear microscopic disease. It also interfaces with modern immunotherapy and can be delivered in palliative regimens using short courses to rapidly alleviate localised discomfort.