Electron beam radiation for cutaneous lymphoma
Radiation therapy uses x-rays and electrons to treat skin tumours. The mycosis fungoides variant of cutaneous T-cell lymphoma (CTCL) is one of the first type of cancers to be treated with radiation therapy only a few years after x-rays were discovered at the end of the 19th century.
Today, radiation therapy can be used to treat individual CTCL lesions (local) or the entire skin surface (total skin).
What is electron beam radiation?
Electron beam radiation is a special type of radiotherapy that consists of very tiny electrically charged particles generated in a machine called a linear accelerator and directed towards the skin.
Orthovoltage (low energy) x-ray therapy has been gradually replaced by electron beam radiation therapy in many centers treating CTCL.
Advantages of electron beam radiation over conventional x-rays
Orthovoltage (low energy) x-rays can effectively treat recurrent cutaneous lymphoma lesions, but its penetration to underlying tissues (blood vessels, muscles, bone marrow) can prove to be a distinct disadvantage if more widespread disease is evident.
In contrast, electron beam therapy delivers radiation primarily to the superficial layers (epidermis and dermis) of involved skin and spares the deeper tissues and organs any radiation effects.
Electron beam radiation is very damaging to the tumour cells but is fairly well tolerated by the surrounding normal skin cells.
How is electron beam radiation administered?
Electron beam radiation can be applied in two ways:
Localised electron beam therapy
- Small areas of the skin to be treated are defined and the electron beam is aimed only at these few areas of the skin surface.
- Typically, between 10 and 15 treatments are delivered and the mycosis fungoides (MF) lesions can be destroyed about 90 percent of the time.
- This type of treatment is valuable in people who have on1y a few problem areas on their skin and is usually used in addition to other types of treatment such as nitrogen mustard ointment, phototherapy or chemotherapy.
Total skin electron beam therapy
- The other way of applying electron beam radiation is to direct it at the entire skin surface of the body. This is also known as total skin electron beam therapy (TSEB). TSEB is used whenever there are large areas of the skin which are problematic.
- Treatment with TSEB is commonly accomplished by the person receiving therapy standing in front of the radiation machine and in a series of positions designed to expose all areas of the body to the radiation beam.
- Alternatively, the patient may stand on a platform which slowly rotates in front of the electron beam.
- A standard approach is to deliver a total of 3,600 cGy in small fractions three times a week for approximately 10 weeks.
- During the course of treatment, measurements of the amount of radiation reaching different parts of the body are made. Some areas of the body such as the hands and feet are prone to receive too much radiation and may need to be shielded during portions of the treatment. In addition, it is often necessary to "boost" small areas on the skin with extra treatments if these areas have not received enough radiation with the TSEB treatment.
There is no sensation or discomfort with electron beam treatment. Most people are able to tolerate the treatments well with minimal or moderate side effects.
How does electron beam radiation work?
- Electron beams kill tumour cells by causing damage to their DNA.
- DNA is the most important part of the cell, because it carries the entire code that makes the cell function and multiply.
- Electron beams can cause breaks in the DNA and make it impossible for the cell to multiply.
- Most of the normal cells in the body don’t multiply fast. But tumour cells do and are more sensitive to damage by electron beam radiation.
- Radiation therapy aims to maximize the number of cancer cells destroyed, while minimizing the damage to nearby normal cells.
Side effects of electron beam radiation for cutaneous lymphoma
- During or soon after therapy, electron beam radiation can cause acute effects, such as fatigue, itching, tanning, and burns (like moderate or severe sunburn).
- Although these acute side effects are occasionally severe, they are self-limited if appropriate supportive therapy is administered in a timely fashion.
- Long-term effects include dry skin, decreased sweating, skin colour changes, loss of scalp hair, and the development of dilated blood vessels (telangiectasis).
- Electron beam radiation may also increase a person's risk of developing skin cancer.
- In addition, the psychological impact resulting from the altered physical appearance (hair loss) due to TSEB is often substantial.