External Radiotherapy

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Radiotherapy, also called radiation therapy or Xray treatment is a type of treatment procedure for cancers in which special rays called ionizing radiation is passed through cancerous cells to kill them.

The ionizing rays destroys the genetic material of the cells making it impossible for them to recover. During therapy, the rays also destroy normal cells, but these cells can usually recover again to function normally since they are healthy cells.

Radiotherapy is generally combined with surgery or chemotherapy. It is usually given after surgery to prevent any recurrence of tumors. It can also be given before surgery to help shrink the tumor and improve surgical outcome. In certain cases, it is also given during surgery (IORT or Intra-operative radiation therapy)

Post-surgery radiotherapy can decrease the risks of recurrence of the tumor by almost 50% and improve the chances of survival.

All types of breast cancers, including Ductal carcinoma in situ (DCIS), Invasive ductal cancer, Invasive lobular cancer and Paget's disease are treated with radiotherapy, usually combined with surgery.

Types of Radiotherapy: There are two main type of radiotherapy depending on how the rays are delivered.

  • External Radiotherapy
  • Internal Radiotherapy (Brachytherapy)

This page is on External radiotherapy. Read about Internal Radiotherapy here - Internal Radiotherapy.

External Radiotherapy

External radiotherapy is the procedure of choice in breast cancer. The rays are delivered from outside the body and targetted carefully at the cancerous area. This type of radiotherapy is also useful in women whose breast cancer has spread to other organs and who require treatment to decrease the pain and discomfort.

The ionizing rays are painless and invisible. The patient does not become radio-active after the treatment procedure.

In most cases, a large machine called a linear accelerator is used to aim a beam of high-energy radiation at the breast affected by the cancer. The radiation beams are arranged tangentially to limit the exposure to underlying heart, lung, and the other breast. The image below shows external radiotherapy to the breast.

External Radiotherapy of the Breast

Procedure of External Radiation: Since there are many methods of delivering radiation, treatment planning is a very important first step.

  • If radiation is given after surgery, the theray is usually started 3-4 weeks after surgery.

    After a lumpectomy, radiotherapy is given to the remaining breast tissue on that side. Radiotherapy is usually given to the whole breast. But sometimes, if the risk of the cancer coming back is low and hormone therapy is planned for at least five years, only a part of the breast tissue around the tumor area may be treated. This is known as partial breast radiotherapy. Lumpectomy, with or without radiation therapy is often referred to as breast conservation therapy.

    After a mastectomy, radiation may be given to the chest wall and the lymph nodes in the armpit (axilla) on that side. This is especially so if the tumor was close to the chest wall or had spread to the lymph nodes or if there is a high risk of recurrence.

    Radiation may also be given to the lymph nodes at the base of the neck or to those behind the sternum (breastbone).

  • The amount of radiation necessary for that particular patient is calculated. The dose is calculated according to the size of the tumor, the stage of the breast cancer and the degree of risk to the surrounding tissue and lymoh nodes. Different tissues can tolerate different amounts of radiation.

  • Before the actual treatment procedure is started, a process called simulation is started to define where to aim the radiation. The patient lies under a large machine called a CT simulator. This machine helps to plan exactly where on the body the rays are directed.

    The areas to receive radiation are marked with either a temporary or permanent marker, tiny dots or a 'tattoo' showing where the radiation should be aimed. Marks may also be drawn on the body with a felt-tipped pen. These should not be washed off for the duration of the treatment. If they do, they are redrawn.

  • The dose of radiation is delivered in divided doses since a single dose may be too strong for the patient. Normally, the doses are given once daily from monday to saturday allowing the patient to rest on weekends. But there are different protocols - in some cases, the doses may be given every alternate day, or in others, the dose may be given 3 days a week. The radiation team decides the best method.

    Treatment takes only a few minutes. There is no pain or itching in the skin or any symptoms felt during or after the procedure although the skin may look slightly red and inflamed. Usually, radiation is given over a 3 - 6 week period.

Besides the usual external radiotherapy, there are two special types of external radiotherapy:

  • Intra-Operative Radiation Therapy(IORT): This type of external radiation is given on the OT table during surgery. It is used to treat localized cancers that cannot be completely removed or that have a high risk of recurring (coming back) in nearby tissues. The healthy tissue is first shielded with special covers and a high energy single blast of radiation energy delivered to the cancerous tissue.

  • Prophylactic cranial irradiation (PCI) : This type of radiation is given to the brain when there is a high risk of spread to the brain.

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