What is Radiation Therapy
Radiation therapy is a painless cancer treatment using high-energy particles or waves such as x-rays, gamma-rays, electron beams, or protons to kill or shrink cancer cells.
Radiotherapy breaks the DNA inside the cancer cells which controls cell growth leading to cell death. While both healthy and cancerous cells are damaged by radiation therapy, the goal is to destroy as few healthy cells as possible through precise radiation aim during treatment. Potential damage to normal cells are considered when planning a course of treatment by understanding the amount of radiation that normal tissue can safely receive thus minimising the potential side effects. Often, radiation therapy is combined with chemotherapy for better treatment outcome. . Radiation is delivered by a machine outside the body (external-beam radiation therapy), or come from a radioactive material placed in the body near cancer cells (Brachytherapyradiation therapy). Systemic radiation therapy uses radioactive substance which travel in the blood to kill cancer cells.
Radiation can be used to cure or shrink early-stage cancer (curative radiotherapy), to stop cancer from recurring or treat symptoms caused by advanced cancer (palliative radiotherapy). It can also be combined with chemotherapy (chemoradiation) or before surgery (neo-adjuvant radiotherapy) as synergistic treatment. Oncologist prescribes type of radiotherapy depends on factors such as: type and size of cancer, location of cancer, general health of patients and many more.
Types of radiotherapy
- External radiotherapy (external beam radiation)
External radiotherapy is delivered through a machine whereby beams are directed into the tumour. Linear accelerator (also known case LINAC) uses electricity to form a stream of fast-moving subatomic particles to kill cancer cells. Other modalities of external beam radiation includes Intensity-modulated radiation therapy (IMRT), Image-guided radiation therapy (IGRT), Tomotherapy, Stereotactic radiosurgery (SRS) and Proton therapy.
- Brachytherapy/ Internal radiotherapy (radiotherapy implants)
Brachytherapy delivers radiation from radioactive implants placed inside or on the body area requiring treatment. It can deliver high dose of radiation while causing less damage to normal tissue as it can be precisely placed at the site of the cancerous tissue.
- Radioisotope therapy (systemic radiotherapy)
Systemic radiation therapy requires patient to receive injection or swallows of radioactive substance or radioactive substance bound to a monoclonal antibody which can travel throughout the body. Radioactive iodine is a systemic radiation commonly used to treat certain thyroid cancer. A monoclonal antibody combined to a radioactive substance helps to target, locate and kill cancer cells. Radioactive drugs such as samarium-153-lexifronam (Quadramet) and strontium-89 chloride (Metastron) are a type of palliative radiation therapy.
At Beacon Hospital’s Cancer Centre, a system called the LINAC is employed to carry out the Intensity Modulated Radiation Therapy (IMRT) and Image Guided Radiotherapy (IGRT).
These are the latest methods of delivering radiotherapy in a very precise manner. It has the advantage of treating cancer with a high dose of radiation while sparing the normal cells or tissues, hence reducing the treatment-related side effects or complications. The LINAC system allows IMRT and IGRT to be customised to treat tumours of different shapes and in different locations throughout the body.
Side effects of radiation therapy
The side effects pf radiation therapy depends on the location of the treated area, dosage of radiation, duration of treatment, patient’s general medical conditions and other treatments given at the same time.
Side effects are divided
- early (acute)
- late (chronic) side effects
- Predictable and expected.
Acute side effects are caused by damage to the rapidly dividing normal cells at the area being treated. These include skin irritation, hair loss, urinary problems, mouth and throat ulcers, and damage to the salivary gland. Chronic side effects occur months to years after treatment and is often localised to the treatment site, examples of chronic side effects are:
- fibrosis (scarring of tissues)
- cognitive decline
- damage to the bowel (radiation enteropathy)
- secondary cancer
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