Vet Announcement : Feline Cutaneous Squamous Cell Carcinoma Study

Contrast-enhanced radiation therapy for cats with cutaneous squamous cell carcinoma on the face

The Southern Animal Referral Centre is inviting candidates for an investigational treatment of cutaneous squamous cell carcinoma on the face. The investigation aims to trial contrast-enhanced radiation therapy (CERT) of these tumours as an alternative to traditional therapies.

Right: Feline under external-beam radiation treatment

Introduction: Cutaneous squamous cell carcinoma is a very common cancer that occurs on the face, particularly on non-haired regions in cats that spend long periods of time in the sun. Currently-accepted treatment protocols include surgery, Strontium-90 plesiotherapy, full-course external-beam radiation therapy and cryotherapy. Disadvantages of each existing protocol exist. Surgery is often fairly radical and has associated postoperative pain, cost, cosmetic effects, relatively frequent recurrence and complications. Strontium-90 plesiotherapy involves several treatments with direct contact by a radioactive disc. It requires repeated anaesthetic episodes and there are significant regulatory issues related to the storage and use of radioactive isotopes. Full-course external-beam radiation therapy is effective, but is not widely available (The Southern Animal Referral Centre currently has the only external-beam deep radiation therapy for animals in Australia). It also requires 15 anaesthetic episodes, which are generally very well tolerated, but issues exists with some clients regarding cost and convenience. Cryotherapy is only effective for relatively small superficial lesions.

Proposed therapy and rationale: Normal radiographic contrast agents work by absorbing more radiation than the surrounding tissues. This led to the idea that if tumours are injected with contrast agents, they would absorb more radiation and become more sensitive to its lethal effect, while sparing normal surrounding tissues. This has been demonstrated in experiment protocols. “dose-amplification” of up to 30-40 times has been observed with some tumours. This may allow curative doses of radiation to be administered to tumours in a single dose, but is limited to fairly superficial tumours. We have experience in a limited number of cases where a single dose of contrast-enhanced radiation therapy has completely eliminated any trace of visible tumour.

Criteria for inclusion of cases: We are inviting candidates for this study. All cats must have biopsy-confirmed squamous cell carcinoma on the face of less than 2 cm in diameter, with no evidence of metastasis, and be otherwise healthy and expected to live at least 2 years. Preoperative blood work is required. Owners must be counseled that other accepted treatments exist and that the proposed treatment is investigational.

Cost to owners: The cost to the owners for consultation, general anaesthetic, radiation treatment, half-day hospitalisation and follow-up is $750 including GST. This does not include the pre-treatment biopsy, blood work or thoracic radiographs. Any further therapies will be charged separately.

Follow-up: We request monthly rechecks with us or the primary care veterinarian.

Results: When published, the owners will be provided with a summary of the study results.

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