Radiation Therapy

Radiation therapy works by directing precisely aimed energy at cancer cells. The radiation damages the genetic material (DNA) inside those cells, making it impossible for them to reproduce. Over the course of treatment, the tumor shrinks as damaged cells die off. Healthy surrounding cells can also be affected, but they typically have a stronger ability to repair themselves than cancer cells do.

Most people receive external beam radiation therapy, where a machine called a linear accelerator delivers beams from outside the body. Treatments are usually given five days a week over several weeks, with each session lasting only a few minutes. Other forms include brachytherapy — where radioactive seeds or wires are placed inside or near the tumor — and newer techniques like stereotactic radiosurgery, which delivers very high doses with pinpoint accuracy in just one to five sessions.

Side effects depend on the area being treated and the dose used. Fatigue is common for many people. Skin in the treatment area may become red or sensitive, similar to a sunburn. Your care team can guide you through managing these effects and will monitor your response throughout the course of treatment. Many people are able to maintain normal daily activities during radiation therapy.

Radiation therapy is one of the most widely used cancer treatments — it plays a role in treating roughly half of all cancer cases at some point. For breast cancer in particular, radiation after a lumpectomy significantly reduces the risk that cancer will return in the same breast, making it a key part of breast-conserving treatment.

Advances in imaging and treatment planning now allow radiation to be delivered with remarkable precision, sparing more healthy tissue than was possible even a decade ago. Understanding what radiation therapy involves can help ease anxiety and make it easier to have informed conversations with your care team about whether it is the right choice for your situation.