Electron beam radiation for cutaneous lymphoma

Introduction

Radiation therapy uses x-rays and electrons to treat skin tumours. The mycosis fungoides variant of cutaneous T-cell lymphoma (CTCL) was one of the first types of cancers to be treated with radiation therapy only a few years after x-rays were discovered at the end of the 19th century.

Radiation therapy can be used to treat individual CTCL lesions or the entire skin surface.

What is electron beam radiation?

Electron beam radiation is a type of radiotherapy that consists of very tiny electrically charged particles generated in a linear accelerator and directed towards the skin.

Electron beam radiation therapy has replaced orthovoltage (low energy) x-ray therapy in many centres treating cutaneous T-cell lymphoma.

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) is a disadvantage if the disease is widespread. In contrast, electron beam therapy delivers radiation primarily to the superficial layers of the skin.

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 localised or applied to the entire skin surface.

Localised electron beam therapy

• The electron beam is aimed at localised areas of cutaneous lymphoma.
• Typically, between 10 and 15 treatments are delivered clearing about 90% of mycosis fungoides (MF) plaques.
• Localised electron beam therapy is used for localised disease in addition to nitrogen mustard ointment, phototherapy or chemotherapy.

Total skin electron beam therapy

• Total skin electron beam therapy (TSEB) directs radiation at the entire skin surface of the body and is used for large areas of cutaneous lymphoma.
• 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.

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.
• Electron beams can cause breaks in the DNA preventing cell function and proliferation.
• Tumour cells are more sensitive to damage by electron beam radiation because of their rapid cell turnover.
• Radiation therapy aims to maximize the destruction of cancer cells while minimising 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 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.
• The psychological impact resulting from the altered physical appearance (hair loss) due to TSEB can be substantial.