Radiation therapy

What it is

Radiation therapy uses focused high-energy rays (photons, or in some centers protons) or radioactive sources to kill cancer cells while sparing as much healthy tissue as possible. Most is delivered from outside the body (external-beam), shaped to the tumor with techniques like IMRT (intensity-modulated) and image guidance. Stereotactic approaches (SBRT / SRS, e.g., Gamma Knife) deliver very high, pinpoint doses in a few sessions. Brachytherapy places radioactive sources inside or next to the tumor (used in prostate, cervical and some other cancers). Radiation is often combined with surgery and/or chemotherapy (chemoradiation).

Why it's done

• Curative treatment for many localized cancers (e.g., early prostate, head & neck, cervix)
• Before surgery to shrink a tumor, or after surgery to destroy remaining cells (adjuvant)
• With chemotherapy (chemoradiation) for cancers such as lung, esophagus and rectum
• Palliation — to relieve pain from bone metastases, bleeding, or pressure symptoms

How it’s given

After a planning (“simulation”) CT scan and careful mapping, treatment is usually delivered in short daily outpatient sessions (fractions) over days to weeks; stereotactic courses use 1–5 sessions. Each session itself is painless and takes minutes. Brachytherapy is a separate procedure to place the radioactive sources.

What to expect

Side effects build up over a course and are mostly local to the treated area (e.g., skin changes, fatigue, sore throat or bowel/bladder irritation), usually easing over weeks after treatment ends. Some late effects can appear months to years later.

Risks & side effects

• Fatigue and skin reactions in the treated area
• Site-specific effects (mouth sores, diarrhea, urinary symptoms, etc.)
• Long-term effects such as fibrosis, or (rarely) a second cancer years later
• Effects on nearby organs — planning aims to minimize these

Alternatives