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Radiation therapy is a type of therapy that uses the energy of ionising radiation to kill abnormal, usually cancer, cells. Although it is also used in the treatment of non-malignant (not cancerous) conditions, its main use is in the treatment of cancer. Cancer radiation therapy can be used as curative, adjuvant, neoadjuvant or palliative therapy and is usually administered in conjunction with chemotherapy. The doctors that specialise in cancer radiation therapy are called radiation oncologists. The radiation oncologist decides the requirement, dosage, frequency and duration of the cancer radiation therapy required based on the type, stage and extent of cancer. After the decision has been made to subject the patient to cancer radiation therapy, a radiation simulation is conducted. The patient is made to lie on a table and their position is adjusted such that the linear accelerator machine is able to aim optimum ionising emission beams to the tumour. The skin overlying the target spot in this position is marked with a small tattoo. Usually, each radiation therapy session lasts 10 to 30 minutes. Side effects after cancer radiation therapy are expected to arise but normally disappear two months after completion of therapy. However, some may persist for longer.

(Read more: Difference between tumour and cancer)

  1. What is radiation therapy?
  2. How cancer radiation therapy works
  3. Preparation for cancer radiation therapy
  4. How radiation therapy is administered
  5. Aftercare following cancer radiation therapy
  6. Contraindications of radiation therapy
  7. Complications of radiation therapy

Radiation therapy is a modality of treatment used to kill abnormal, generally cancerous, cells with the energy of ionising radiation that is usually delivered by a linear accelerator. Radiation therapy is used in the treatment of non-malignant neurological conditions like trigeminal neuralgia and acoustic neuroma and dermatological conditions like keloids and cosmetic hair removal. However, the role of radiation therapy in non-malignant conditions is limited due to the plethora of possible side effects. Radiation therapy is often given in conjunction with other cancer treatments like surgical resection, chemotherapy and even immunotherapy. The doctors that specialise in cancer radiation therapy are called radiation oncologists. Radiation therapy of cancer can be:

  • Curative radiation therapy: In some cancers, radiation therapy is the mainstay of treatment and superior to other methods in terms of clinical outcomes.
  • Adjuvant radiation therapy: Adjuvant radiation therapy refers to the radiotherapy given after surgical treatment or chemotherapy to prevent the cancer from returning.
  • Neoadjuvant radiation therapy: This type of radiation therapy is given to a tumour before surgical resection or chemotherapy, with the aim to shrink it and improve the clinical outcome of the main treatment.
  • Palliative radiation therapy: Cancer radiation therapy can be used in palliative (end of life) care of a cancer patient. The aim of radiation therapy in palliative care is not to give high curative doses but rather small doses of radiation that do not produce any discomfort or side effects. The aim of this radiation therapy is to:
    • Relieve bone pain due to metastasis to the skeletal system
    • Treat spinal cord and nerve compression
    • Address the symptoms of cancer within the brain
    • Shrink a tumour to relieve pressure or a blockage
    • Stop bleeding
  • Total body irradiation (TBI) radiation therapy: Ionising radiation is administered to the entire body of the patient except for the lungs, which are shielded to protect them from radiation-induced lung injury, before conducting a bone marrow replacement procedure. This type of radiation therapy suppresses the body’s immune system and reduces chances of rejection of the donor bone marrow or blood stem cells being transplanted by an immunological reaction.
  • Brachytherapy radiation therapy: Brachytherapy is also known as internal radiation therapy. In this type of cancer radiation therapy, a sealed source of radiation (like brachytherapy beads used in prostate cancer) is placed inside or next to the site of cancer that has to be treated. This method of cancer treatment has proven highly effective in some cancers (like cervical cancer, breast cancer, prostate cancer, etc.) and equivalent in efficacy to surgical management. Brachytherapy implants can be permanent or temporary.

In order to reduce radiation exposure to the organs surrounding the cancer or tumour site, i.e. the organs through which radiation emission must travel to reach the target sites, the ionising radiation beams are shaped and aimed from several angles of exposure to intersect at the tumour. This way, the tumour or target site receives the maximum ionising radiation and the surrounding healthy tissue is spared. The ionising radiation emitted by the linear accelerator causes damage in the DNA of target cancer cells. The DNA damage produced prevents cancer cells from undergoing replication, thus halting their growth and spread. Lymph nodes adjacent to the target organ that receive its lymphatic drainage may also need to be subjected to ionising radiation. A margin of safety is taken into consideration and a small extent of surrounding seemingly healthy tissue is also radiated.

The radiation oncologist will meet with the patient and assess them medically. The doctor will take a medical history, conduct a physical examination and look at reports of laboratory investigations and radiological imaging films. Taking into consideration the type, stage and extent of the cancer, as well as the patient's general health, the doctor will decide what dosage and frequency of cancer radiation therapy is best suited for the treatment of the patient’s cancer. Radiation therapy may even be reserved for use at a later stage and other types of cancer treatment may be tried first.

Once it has been decided that the patient is to undergo cancer radiation therapy, they will undergo radiation simulation.

In radiation simulation, the patient will be made to lie on the table they will lie on in all future sessions. They will be positioned in such a manner as to make the tumour most accessible to the ionising radiation emission beams. This position may require the use of pillows, cushions, other supportive structures and restraints to achieve. CT scans or X-rays will be taken in this position to evaluate the optimal position. After this is determined, a small tattoo (the size of a freckle) is made on the skin to signify the tumour spot. In some cases, this tattoo may not be permanent.

The dosage, frequency and duration of cancer radiation therapy needed depend on the type, stage and extent of cancer. Patient tolerance may also be a factor in this decision. Usually, each cancer radiation therapy lasts 10 to 30 minutes and although variable, typically five sessions per week for 1 to 10 weeks is the norm.

In each session, the patient is made to lie on the table and, with the help of supportive structures and restraints, positioned in the exact same manner as that in the radiation simulation. The patient is made to wear protective covering, shields and goggles that help spare the surrounding tissue and protect it from harmful and unnecessary radiation exposure.

After positioning, the linear accelerator machine used in radiation therapy is fired up. This machine focuses beams of ionising radiation directly at the tumour or target site. The machine may rotate around the table to aim radiation emission beams from all angles. The machine produces a buzzing sound and can be disconcerting for the patient. No pain is anticipated in the cancer radiation therapy session. The radiation oncology team is present in an adjoining room and can be spoken to, if necessary, through the intercom.

Cancer radiation therapy can leave the patient feeling tired, emotionally distressed and with sensitivity around the treatment site. To manage these symptoms, it is recommended for the patient to remain well hydrated by drinking plenty of fluids, eating a healthy and balanced diet, talking with friends and family and staying out of the sun to avoid possible photosensitivity reactions.

(Read more: Diet for cancer patients)

Skin care while cancer radiation therapy is recommended as follows:

  • Avoid sun exposure, especially of site being treated
  • Wash the skin over the treatment site daily with a mild soap and warm water
  • Keep the skin over the treatment site dry
  • Avoid extremes of temperature to the skin over the treatment site
  • Avoid applying any lotions, creams, deodorants, perfumes, aftershaves and cosmetics on the site where radiation is being given
  • Do not rub or remove the treatment marks

While some of these contraindications are absolute (which means if they’re present, cancer radiation therapy can not be done at all), some are relative and do not necessarily imply a complete impossibility of the procedure. Contraindications to cancer radiation therapy include, but are not limited to:

  • Pregnancy
  • Connective tissue disorders (CTDs): The use of cancer radiation therapy may not be contraindicated with all types of connective tissue disorders (CTDs). In case of a CTD with significant vasculitis, cancer radiation therapy is absolutely contraindicated. Some examples of connective tissue disorders in which cancer radiation therapy is contraindicated include:
  • Significant pre-existing lung disease: In case the diffusion capacity of the lungs is severely reduced, cancer radiation therapy is contraindicated.
  • Prior radiation therapy in the same part of the body
  • Presence of a pacemaker in the cancer radiation therapy field

Irrespective of the type of cancer radiation therapy received, certain side effects are expected. While most of these disappear two months after completion of cancer radiation therapy treatment, some can linger for longer. Any complications following cancer radiation therapy treatment should be reported to the doctor immediately. Common side effects in the early phase include, but are not limited to:

Sometimes complications of cancer radiation therapy can linger for six months or longer after completion of cancer radiation therapy. Sometimes these can appear years later as well. These include, but are not limited to:

  • Mouth problems
  • Joint problems
  • Lymphoedema, or tissue swelling
  • Infertility
  • Possible secondary cancer, like rectal cancer

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