WEB Vetnews May 2015

Lead Article I Hoofartikel

C ancer T reatment <<< 6

Soft tissue sarcomas are derived from the mesenchymal cells There are many tumours in

(9 different sizes and

male/female are available) together with a long acting 8 hour sunscreen.

this category, e.g. liposarcoma, chondrosarcoma, fibrosarcoma , peripheral nerve sheath tumours and more. Biologically they generally behave in a similar way; usually they are found in the subcutaneous tissue, they grow slowly, usually do not metastasise, but often recur after surgical excision. These tumours require very wide surgical margins as they are surrounded by a pseudocapsule that allows the cancer cells to escape. If they are radiated pre-operation (consolidation), they are easier to remove in their entirety. It is easy to make the radiation field very much larger than the surgical field and if the area is also radiated post-surgery, the success of the treatment is greatly enhanced. Because these tumours grow more slowly than carcinomas, they require a higher total dose of radiation. Although in humans the radiation doses have different limits for the different types of tissue, this has not yet been described in the dog and cat. For successful treatment of cancer in dogs and cats remember the following: • Early diagnosis is essential • Educate pet owners to recognise the following - small non-healing skin lesions specially in non-pigmented skin - lumps in abnormal locations The most gratifying effect of radiation for the animal and their owner is that of the palliation of pain. The previously depressed animals start eating, playing and grooming again. Acknowledgements • Colleagues for your referals and the care of your patients. • Liesl du Raan (radiation therapist) for expertise, interest and unfailing care for each patient. • Scientists whose work I have read. • You, the reader for your interest. v

Cats are naturally nocturnal

Histiocytoma The first photograph shows the tumour at presentation, patient not eating. Treated with radiation therapy (12 x 2 Gys). Second photograph taken 80 months later, no recurrence.

animals, so the cats that are at risk should be confined to the sunniest room

Squamous cell carcinomas (SCC) in dogs and cats This cancer is caused by high levels of exposure to the B-fraction of ultra- violet radiation (UVB), on susceptible non-pigmented animal skin. South Africa has one the highest UV levels recorded in the world. Factors that influence UVR levels across the globe include altitude, intensity and duration of sunlight, and the thickness of the ozone layer. The UVB energy enters the basal cell of the epidermis and mutates the DNA, which results in the uncontrolled proliferation of the squamous cells. The normal histology of the well-ordered squamous cell tissue changes from its regular pattern to one of disintegration, ultimately leading to the development of a SCC. Typically the clinical lesions are treated with linear accelerator electron radiation therapy with/without surgery. The earlier this condition is recognised and treated the better the prognosis. To prevent the solar exposure in dogs, ultra violet Lycra body suits are worn

in the house, with a special plastic film that blocks the UV, but allows the visible light and infrared energy to pass through. The cats are fed in this room at 08:00 and released at 17:00. Cutaneous Mast Cell Tumours (MCT) MCT are visibly the most difficult tumours to judge and a fine needle aspirate of any suspicious “lump” should be examined; confirmation using a biopsy may be needed . The pathology report is useful for understanding how aggressive the tumour is, by its mitotic index and the description of the cells. Often the pathologists do not grade the tumour, as the prognosis and the eventual outcome are vastly different. Radiation for the primary cutaneous tumour is a most effective way to consolidate the tumour before surgery. If the tumour has metastasized (detected by use of ultrasound examination) both radiation for the primary and chemotherapy for the secondary tumours is necessary. The MCT patient shown in the photo­ graphs was graded as Grade 3 and yet did not

metastasise; some of the Grade 2 MCT did meta­ stasise.

Mast Cell Tumour, Grade 3 The first photograph shows the MCT at presentation; the second photograph was taken three years later, after radiation, surgery and post- surgery radiation (total radiation 10 x 3 = 30 Gys)

vet nuus • news

7

Mei/May 2015