Radiation therapy

Radiation therapy is the treatment of choice for brain tumours, nose tumours and head or neck tumours.

Overview

Radiation therapy is a treatment that is usually offered when a pet has been diagnosed with cancer. It works by killing cancer cells via a powerful x-ray or electron therapeutic beam while minimising effects on healthy tissue cells. X-ray beams are used for tumours deep within the body and electron beams are used for skin tumours. Occasionally CT or MRI images are used to help position a tumour and isolate the cancerous tissue. And pets undergo general anaesthesia for treatment.

Signs

Side effects can be categorised into immediate or late effects.

Common immediate side effects of radiation therapy:

• Skin redness
• Skin moistness and irritation
• Redness, ulceration or blistering of mucous membranes (gums, tongue, cheeks)
• Hair loss, flaky skin and shedding of the outer skin layer

Most immediate side effects require supportive care at home and resolve 3-4 weeks following treatment.

Common late side effects of radiation therapy:

• Scarring
• Ulcers
• Darkened skin
• Tissue death or shrinkage
• Nerve damage

These late side effects are rare and occur months to years after radiation therapy. Unfortunately, when these side effects occur they are progressive and irreversible.

Indications

Common cases where radiation therapy may be recommended:

• For tumours that cannot be accessed surgically such as the brain
• For tumours that cannot be fully removed surgically
• For tumours where cancer cells extend beyond the surgical site

Radiation therapy can be used alone or with other treatments such as chemotherapy. It is the treatment of choice for brain tumours, nose tumours and head or neck tumours.

Palliative Radiation Therapy

This type of radiation therapy is administered with the intent of reducing the pain associated with an incurable tumour. These pets typically would not benefit from a more aggressive definitive course of radiation treatment. This form of therapy is used widely in dogs with osteosarcoma where 75-90% of dogs experience pain relief and improvement in mobility around 14 days from starting treatment. Pain relief usually lasts around 3-4 months. Other cancers that have benefited from this include oral tumours, nasal tumours, thyroid carcinomas and soft tissue sarcomas.

Administration

Radiation therapy is administered under general anaesthesia and over multiple doses over multiple days, throughout a 3-4 week period.