Radiotherapy, or radiation therapy, is a medical treatment that uses high-energy radiation, such as X-rays, to target and kill cancer cells or shrink tumors. It works by damaging the DNA inside cells, which prevents them from growing and dividing. While it can affect both cancerous and healthy cells, cancer cells are generally more sensitive to radiation.

Radiotherapy can be used in different ways:

• Curative treatment: To try to completely remove or shrink a tumor.

• Palliative treatment: To reduce symptoms and improve quality of life, especially in advanced cancer cases.

• Adjuvant treatment: After surgery to destroy any remaining cancer cells and reduce the chance of cancer coming back.

There are two main types of radiotherapy:

1. External beam radiotherapy: This is the most common type, where radiation is delivered from outside the body, targeting the tumor.

2. Internal radiotherapy (Brachytherapy): This involves placing a radioactive source directly inside or very close to the tumor.

The treatment is typically given in several sessions over a period of weeks, and while it can cause side effects like skin irritation or fatigue, these are usually temporary and depend on the treatment area.