What is radiation therapy?

Radiation therapy is a type of treatment for cancer, which involves the use of beams of high-energy ionizing radiation rays to target and destroy the cancer cells and stop their uncontrolled growth. X-rays, Gamma rays, and Charged particles are used for radiation in treating cancer.

Radiation therapy also referred to as radiotherapy is a treatment for cancer that uses high doses of radiation that kill the cancer cells and shrink the tumors.

The use of radiation in the treatment of cancer forms a very important part of cancer management. It may be used alone or in combination with cancer surgery or with chemotherapy or with both to cure cancer.

Though radiation treatment has its side effects, it has done more good than harm in the treating of cancer. Its benefits and effectiveness far outweigh the risks.

More than half of cancer patients are given radiation therapy for their malignancy, either for cure or to give symptomatic relief. That means, more than one million cancer patients are given radiation treatment every year. This radiation statistic only signifies its importance in cancer therapy.

Types of Radiation

More than half of all people with cancer receive radiation therapy as part of their cancer treatment. Doctors use radiation therapy to treat every type of cancer either as treatment or to give symptomatic relief.

Also referred to as radiotherapy for cancer, radiation can be external or internal. Each of these types of radiation has its indications and sometimes both types of radiation may be used to cure the patient.

Internal radiation for cancer, also called brachytherapy, involves placing an implant or “seed” containing radioactive isotopes inside the tumor or near it. The patient is required to be hospitalized for this type of radiation treatment.

External radiation makes use of a radiation machine to give radiation treatment from the outside to the patient.

The type of radiation therapy that your doctor chooses for you depends on the following factors:

  • The type of your cancer
  • The tumor’s size and  stage
  • Its location in the body
  • Your general health and medical history such as your age and other accompanying medical conditions
  • Whether you will also be treated with other types of cancer treatments

External Beam Radiation Therapy

External beam radiation therapy (EBRT) is the most commonly used form of radiation oncology treatment. It delivers a beam or several beams of high-energy x-rays to a patient’s tumor.

This therapy is called external because the beams are generated outside the patient, usually by a linear accelerator and targeted at the cancer site.

Radiation does not hurt, or burn when it enters the body. Typically, people have prescribed treatment sessions 5 times per week,

External beam radiation therapy is a local cancer treatment and not systemic, which means its effect is localized to a specific part of your body, which has developed cancer. For example, for lung cancer, radiation is given only to your chest, not to your whole body.

Internal Radiation Therapy

In internal radiation therapy, a radioactive implant, which is the source of radiation is embedded inside your body. The radiation source can be solid or liquid.

Internal radiation therapy that has a solid source is called brachytherapy. The solid source of radiation may be in the form of seeds, ribbons, or capsules and are placed in your body, usually in or near the malignant tumor.

This treatment may require a brief hospital stay and it is carried out under anesthesia to block the pain you may feel when the radioactive sources are implanted inside your body.

Like external beam radiation therapy, brachytherapy is a local treatment and treats only the specific part of your body, which has cancer.

With brachytherapy, the radiation source in your body will give off radiation for a while.

Brachytherapy is often indicated to treat cancers of the head and neck, breast, cervix, prostate, and eye.

How does radiation work to treat cancer?

Radiation destroys the genetic composition (the DNA) of the cancer cells, thereby making it impossible for them to grow and multiply. Radiation does this either by a direct destructive action on the DNA or by the creation of free radicals inside the cancer cells, which destroy the DNA.

Once the DNA of the cancer cells is destroyed, they stop proliferating and die. They are then removed by the body.

Radiation therapy does not kill cancer cells immediately at the start of therapy. It takes days or sometimes weeks of radiotherapy before DNA in the cancer cell is damaged enough for cancer cells to die. They keep dying for several weeks or months even after radiation therapy is completed.

The draining lymph nodes are also targeted if there is the slightest suspicion of their involvement. This procedure is performed by a trained radiation oncologist and is painless.

Besides the cancer tissue, radiation also destroys the neighboring healthy tissue. The healthy tissue cells, however, recover after radiation and begin their normal function. To allow time for the normal cells to recover, radiation is given at intervals.

Giving radiation has to be precise. Digital radiological reports of studies (such as CT scans, MRIs, PET, ultrasound ) are referred to before treatment, to chalk out the area to be radiated. Exactly the same area has to be targeted at each radiation treatment. The patient has to be in the same position and angle. Skin marks or skin tattoos are used to mark out the area for the purpose.

Radiation for cancer is used for almost all tumors such as tumors of the brain, lung, breast, uterus, cervix, prostate, pancreas, and stomach. This treatment is also useful to treat lymphoma and leukemia.

Indications of radiation treatment in cancer

In treating cancer,

  • Radiation may be used before cancer surgery to shrink the tumor for better results of surgery. This radiation therapy is called neoadjuvant radiation.
  • Radiation may be given during surgery. This is called intraoperative radiation and is indicated when the normal tissues close to the tumor, are extra sensitive to radiation and cannot be risked to radiation exposure. At such times, the normal tissues close to the tumor are covered and shielded from radiation to avoid damage to them. The tumor is then radiated.
  • Radiotherapy may be given after cancer surgery, for a better prognosis. This is called postoperative radiation or adjuvant therapy.
  • Radiation is at times, also used alone in treating cancer as the only (primary) treatment for cancer.
  • Most of the time, radiation for cancer is used in combination with chemotherapy for treating cancer. Though more cancer cells are destroyed with this therapy, the side effects are also more. This type of cancer therapy is called chemoradiation.
  • At times, radiation for cancer is used as palliative treatment for giving symptomatic relief to the patient. Such examples are metastasis to the brain, spinal cord compression due to a tumor, and occlusion of the esophagus by a tumor.

Dose and Unit of Radiation

Doses of radiation to treat cancer are measured in a unit called gray. One gray is the amount of radiation that is absorbed by one kilogram of human tissue. Doses of radiation differ depending on the indication of radiation.

The dose of radiation depends on the following data:

  • The general condition of the patient
  • Type of cancer
  • Stage of cancer
  • Sensitivity of the type of tumor to radiation
  • Sensitivity of the normal tissue adjacent to the tumor
  • Whether radiation is being given for cure or prevention.

Fractionation is giving radiation therapy over intervals of time. Radiation is normally given at weekly intervals, but there may be variations as required. Radiation therapy is spread out with the purpose of giving normal tissue that has been damaged during radiation, time to recover.

What is the success rate of radiation therapy?

Patients with early stages of the disease do well with either brachytherapy or external beam radiation. Success rates of around 90% or higher are achieved with either approach.

With stereotactic radiation treatment, more than eight in ten patients (84%) survived at least 1 year, and four in ten (43%) survived 5 years or longer. The average overall survival period was 42.3 months.