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How does it work?

How does Brachytherapy work?

Brachytherapy works by placing a source of radiation directly in, or next to the cancerous tumor inside the body.

This allows the radiation to be precisely targeted to ensure the tumor receives the most effective dose to kill the cancer cells.1 This ‘tailored approach’ also reduces the risk of any unnecessary damage to healthy tissue and organs that are close to the tumor, therefore reducing potential side effects.1

Doctors plan and deliver brachytherapy by using computer software to determine how and where the radiation should be delivered in the body.1 The radiation is delivered precisely and accurately to the tumor by the use of special applicators. The applicators are carefully placed in the correct position by using various imaging techniques, such as ultrasound and magnetic resonance imaging (MRI) scans.1 A small source of radiation, usually held on the end of a wire, is delivered to the treatment site via the applicators.

Radiotherapy works by damaging the genetic material (also known as DNA) of cancerous cells.2 When brachytherapy is delivered to a tumor, the radiation damages the genetic material, which prevents the cancer cells from growing and multiplying.

Types of brachytherapy

The way the radiation is delivered with brachytherapy depends on a number of factors. These include:

  • The location of the cancer in the body
  • The size of the tumor
  • Whether the cancer has spread to other parts of the body or not

There are two main types of brachytherapy using radioactive sources:

Temporary brachytherapy - sources of radiation are placed inside or next to the tumor for a short amount of time, typically a few minutes.1 These sources of radiation usually use a high rate or ‘intensity’ of radiation, and are known as high dose rate (HDR) sources. Temporary HDR brachytherapy is often used to treat cancer of the cervix, lungs, breast and prostate.1 It is usually performed on an outpatient basis, meaning you won't need an overnight stay in hospital. A small number of sessions of treatment are typically needed, which can take place over a period of just a few weeks.3

Permanent brachytherapy - sources of radiation are placed inside the tumor on a permanent basis.1 This type of brachytherapy is mostly used in the treatment of prostate cancer -sometimes known as ‘seed therapy’. The radiation sources look like tiny seeds (about the size of a grain of rice). These seeds use a low rate or ‘intensity’ of radiation to kill the cancer cells. The seeds are known as low dose rate (LDR) sources. The level of radiation given out by the seeds gradually decreases over time to almost nothing (most of the radiation is released over 3 months, and by 9 months the seeds are inactive).1

In addition to LDR and HDR brachytherapy, radiation can also be delivered in short pulses of radiation (e.g. once an hour). This is termed ‘pulsed dose rate’ (PDR) brachytherapy and is a type of temporary brachytherapy. PDR brachytherapy is often used to treat gynecological and head and neck cancers. PDR brachytherapy is commonly used to simulate the overall rate and effectiveness of LDR treatment.4

New - Electronic brachytherapy:

Electronic brachytherapy (EBT) is a relative new form of brachytherapy using radiation generated by an x-ray tube instead of radiation from a radioactive source as described above. EBT is primarily used for the treatment of skin cancer. EBT can be applied by simply placing the device containing the x-ray tube over the skin tumor. A huge advantage of this type of brachytherapy is that the shielding requirements, for example for the treatment rooms, are less and patients do not have to be treated in a vault.

References

1. Patel RR and Arthur DW. Hematology/Oncology Clinics of North America 2006;20(1):97–118.
2. National Cancer Institute. Available at: www.cancer.gov/cancertopics/factsheet/Therapy/radiation. Accessed 2 February 2011.
3. Stewart AJ and Jones B. In: Brachytherapy: applications and techniques. Devlin PM (Ed). Philadelphia, PA, LWW. 2007.
4. Viswanathan AN, et al. In: Brachytherapy: applications and techniques. Devlin PM (Ed). Philadelphia, PA, LWW. 2007.