How Does Radiation Work?

Radiation therapy, also known as radiotherapy, is a common cancer treatment that uses radiation to kill cancer cells. These rays are directed precisely to the tumor or affected area, sparing the surrounding healthy tissues as much as possible. The goal is to deliver enough radiation to damage or destroy cancer cells while minimizing the impact on normal cells nearby.

How Does Radiation Work?

Radiation therapy acts by damaging the DNA inside the targeted cancer cells. When the high-energy rays pass through the cancerous tissue, they interact with the DNA molecules, causing breaks in the strands. These breaks interfere with the cells' ability to replicate and divide, effectively stopping the growth and leading to the death of cancer cells.

Normal cells also experience some radiation damage, but unlike cancer cells, they have an advantage in recovery. Healthy cells can repair themselves better than cancer cells, allowing them to bounce back from the radiation's effects. The treatment is typically planned to allow time for healthy cells to recover between radiation sessions, reducing the risk of long-term damage to healthy tissues.

Types of Radiation Therapy

External Beam Radiation Therapy is the most common type of radiotherapy. With EBRT, a machine directs beams of high-energy radiation toward the tumor. The energy may be X-rays (most common), electrons or protons. Precision is vital with EBRT. Your radiation oncologist will design a treatment plan to target the tumor with radiation while avoiding your healthy tissue.

There are many forms of EBRT:

• 3D conformal radiation therapy uses CT scans and computer software to create a 3D model of the tumor. Using the model as a guide, the machine directs radiation beams that target the cancer site while sparing healthy tissue.
• Intensity-modulated radiation therapy (IMRT) is a more advanced form of radiation therapy. IMRT uses many radiation beams that vary the dose intensity. It delivers a higher radiation dose to the tumor and lower doses to healthy tissue.
• Arc-based radiotherapy is a form of IMRT. It directs energy beams of varying intensity in a rotational arc-like pattern. This method delivers radiation faster than traditional IMRT. Volumetric modulated arc therapy (VMAT) and tomotherapy are two forms of arc-based radiotherapy.
• Image-guided radiotherapy (IGRT) is a form of EBRT in which the radiation machine obtains a low-dose X-ray or mini CT scan before each treatment. This image helps align the treatment site, resulting in more precise radiation delivery.
• Particle therapy uses radiation therapy that consists of protons instead of photons (X-rays). For certain people, protons can deliver the same radiation dose to the tumor and reduce radiation dose to healthy tissues.
• Stereotactic radiosurgery, or Gamma Knife radiosurgery, uses high doses of focused radiation to destroy small brain tumors with surgical precision. Unlike surgery, it doesn’t require cutting. Typically, this treatment takes one to five days.
• Stereotactic body radiation therapy (SBRT) uses high doses of focused radiation to destroy tumors outside of your brain. Like stereotactic radiosurgery, it eliminates tumors with surgical precision but without actual surgery.
• Intraoperative radiation (IORT) delivers radiation during surgery. After a tumor has been removed surgically, IORT destroys any remaining cancer cells that aren’t safe to surgically remove.

Internal Radiation Therapy (Brachytherapy): In this approach, radioactive sources are placed directly inside or very close to the tumor, delivering a higher dose of radiation to the cancer cells while sparing surrounding tissues. Brachytherapy is often used in cancers of the prostate, cervix, and certain other organs.

• Brachytherapy implants a solid radioactive source, or “seed,” inside or beside a tumor. The source releases radiation to a small area to kill cancer cells. Some implants release low doses for longer periods (weeks). Others may release high doses for shorter periods (minutes). Some implants used in brachytherapy are temporary. Others stay in your body forever. Eventually, they stop releasing radiation.
• Systemic therapy sends liquid radioactive material through your blood to find and destroy cancer cells. Some forms are swallowed. For others, you’ll receive an injection through a vein (IV). Treatments include radionuclide therapy (radioimmunotherapy). With radioimmunotherapy, a radioactive protein recognizes specific cancer cells, attaches to them, and then releases radiation to kill them.

Radiation therapy may cause side effects, depending on the treated area and the individual's overall health. Common side effects include fatigue, skin changes, and localized reactions. The radiation oncology team at Arizona Blood and Cancer Specialists works closely with the patient to manage and alleviate any side effects that may arise during the treatment process.