Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. Radiation therapy is a crucial component of cancer treatment and has been employed for many years. External-beam radiation therapy involves directing high-energy beams from outside the body onto the tumor. Internal radiation therapy (brachytherapy) is another approach where a radioactive source is placed directly inside or very close to the tumor. The choice between these methods depends on the type, location, and stage of the cancer.

Radiation therapy is often used with other cancer treatments, such as surgery, chemotherapy and immunotherapy. The combination of these treatments is known as a multidisciplinary approach, and the specific combination depends on the individual characteristics of the cancer and the patient.

While radiation therapy is effective in targeting and destroying cancer cells, it can also affect normal, healthy cells in the process. This is why careful planning and precision are crucial to minimize damage to surrounding tissues. Advances in technology and techniques have improved the precision and reduced side effects associated with radiation therapy over time.

At high doses, radiation therapy kills cancer cells or slows their growth by damaging their DNA. Cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and removed by the body.

Radiation therapy does not kill cancer cells right away. It takes days or weeks of treatment before DNA is damaged enough for cancer cells to die. Then, cancer cells keep dying for weeks or months after radiation therapy ends.

The main types of radiation therapy include:

1. External-Beam Radiation Therapy (EBRT) :This is the most common form of radiation therapy, where high-energy beams are generated by a machine outside the body and directed towards the tumor. The patient typically lies on a treatment table, and the radiation machine is adjusted to target the tumor from various angles.
   1. Conventional RT : involves delivering a uniform dose of radiation to the entire area where the tumor is located using simple techniques.
   2. 3 D Conformal RT (3DCRT) : Multiple radiation beams are then directed from different angles to conform more closely to the shape of the tumor, reducing exposure to healthy surrounding tissues.
   3. Intensity-Modulated Radiation Therapy (IMRT): IMRT is a more advanced form of external-beam radiation therapy where the intensity of the radiation beams is modulated to conform to the shape of the tumor, minimizing exposure to surrounding healthy tissues.
   4. Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT): These techniques involve delivering very precise and intense doses of radiation to small tumors or specific areas in the body. Despite the names, these procedures are non-surgical and are often used for tumors in the brain (SRS) or in other parts of the body (SBRT).

2. Brachytherapy : In this approach, radioactive sources are placed inside or very close to the tumor. This can be achieved by using implantable devices or by directly inserting radioactive material into body cavities, such as the cervix or the breast. Brachytherapy allows for a more targeted delivery of radiation.

Radiation therapy can be used in various types of cancer like brain, head and neck, lung, breast, gyanecological and genitourinary cancers.

Curative Intent:

Primary Treatment: Radiation therapy can be the primary treatment for certain types of cancer. It is often used with curative intent, aiming to eliminate the cancer or reduce the tumor size ,for example cervical cancer and some head and neck cancers.

Neoadjuvant Therapy:

Pre-Surgery: In some cases, radiation may be administered before surgery to shrink tumors and make them more manageable for surgical removal, for example Esophageal cancers.

Adjuvant Therapy:

Post-Surgery: After surgical removal of a tumor, radiation therapy may be used as adjuvant therapy to target any remaining cancer cells in the surrounding area. This helps reduce the risk of cancer recurrence, for example breast cancer.

Palliative Care:

Symptom Relief: Radiation therapy is often used to relieve symptoms and improve the quality of life for patients with advanced cancer. It can help shrink tumors that are causing pain, bleeding, or other issues.

Combination with Other Treatments:

Multimodality Approach: Radiation therapy is frequently combined with other cancer treatments, such as surgery, chemotherapy, precision oncology (targeted therapies), and immunotherapy, to create a comprehensive and effective treatment plan.