Cancer is a major cause of illness and death in dogs.

Whilst some forms of cancer, for example mammary tumors, are ubiquitous in the dog population, other types of the disease seem to show predispositions for different breeds of dog.

In the past, cancer of the lymphoid system and blood forming organs (lymphosarcoma and lymphoid leukemia) have been documented as showing a familial incidence in the Bullmastiff. There is also concern that the breed may suffer from other tumors including those affecting bone (osteosarcoma) and the skin (mast cell tumor).

In order to evaluate the importance of such problems in the breed we seek to collect information on affected dogs. The aim of this study is to establish whether a problem truly exists and to provide a basis for more detailed research into any problems identified.

We can only undertake this study with the full support and co-operation of Bullmastiff Owners & Breeders.

HOW CAN YOU HELP?

I. If you have lost a Bullmastiff as a result of cancer in the past.

The details of your dog could be of value to the study. Please complete the study form providing as much detail as possible. Your veterinary surgeon may be able to assist with medical details.

2. If your Bullmastiff develops cancer.

In the unfortunate event of your animal becoming ill, you must obviously seek advice from your veterinary surgeon, but, once a diagnosis is established we would ask you to complete the survey form with the assistance of your veterinary surgeon.

If a tumour is suspected, we would be pleased to discuss the case with your veterinary surgeon and we will process biopsy material to assist in establishing a diagnosis free of charge.

For a study form : mailto:Morvern@aol.com alternatively, by post from addresses at bottom of page

Study results to November 1997

FURTHER POINTS

A fundamental necessity of the investigation is an accurate diagnosis of each recorded cancer or illness. We will be pleased to discuss tumor related problems with your veterinary surgeon where necessary.

Any information given will be completely confidential.

The information will be held at Cambridge Veterinary School where it will be confidential to the Oncology staff.

The results will only be analysed collectively and no individual will be identifiable from any report.

PLEASE HELP WITH THIS IMPORTANT STUDY

OSTEOSARCOMA

(PRIMARY MALIGNANT BONE TUMORS) OSTEOSARCOMA is a relatively common tumor which affects the long (limb) bones of the larger breed of dog. The incidence of these tumors increases proportionally with the size of dog and the problem is most significant in the giant breeds.

The most common sites for the development of such tumors in order of frequency are:

Lower radius or forearm just above the 'wrist'

Upper humerus just below the shoulder

Lower femur and upper tibia just above and below the stifle / knee

Lower tibia just above the hock

Proximal femur just below the hip

These tumors usually arise in the 'metaphysic' of the bone, the site where most growth occurs during development of the pup to adulthood. This may be a significant factor in the cause of bone tumors.

The growth of the tumor within the bone results in destruction of the normal architecture (and strength) of that bone. Eventually this process may lead to a fracture of the bone at the tumor site. The tumor may attempt to produce new bone but this is generally haphazard and poorly structured.

THE SIGNS of a bone tumor are:

Pain, leading to a progressive lameness, many animals are eventually unable to bear weight on the affected limb swelling of the bone at the site of the tumor.

On an X-ray of the affected bone, these tumors produce characteristic changes: there is a mixture of bone destruction and irregular new bone production.

DIAGNOSIS: The diagnosis is usually made on the basis of X-ray findings and this is sufficient in the classical case, but a bone biopsy may be indicated if the presentation or appearance of the lesion is unusual in any way.

(The majority of such tumors actually originate from osteocytes and are therefore osteosarcoma. Fibrosarcoma, chondrosarcoma haemangiosarcoma and other sarcomas on occasion present in a similar fashion, hence, in the absence of a histological diagnosis the term 'primary malignant bone tumor' is preferred.)

TREATMENT AND PROGNOSIS

Unfortunately the prognosis for osteosarcoma in the dog is poor.

At the primary site the tumor causes significant pain and weakening of the bone which may progress to a pathological fracture.

These tumors are also highly malignant and frequently spread via the blood stream to distant tissues and organs. The lungs are the most common site for development of secondary tumors (metastases) and this occurs in over 90 percent of cases usually within 6 months of diagnosis.

The local problems can be addressed by amputation of the limb but post-amputation survival times are short, on average 3 - 6 months. A more recent alternative to amputation is local resection of the affected bone and placement of a bone graft.

Limb salvage is only feasible in a small number of carefully selected cases, criterion for selection depending upon the site of the tumor (radius most favourable), the extent of the tumor within the bone, and the absence of soft tissue invasion. Limb salvage is not an "easy option" the animal will require intensive treatment and monitoring for several months following the surgery. Repeated surgeries may be required to stabilise the graft or plate. Finally although, this procedure saves the limb it does not address the problem of metastatic disease.

CHEMOTHERAPY Cytotoxic drugs such as Doxorubicin and Cis-platin have little to no effect on the primary tumor but have been shown to delay the development of pulmonary metastases following surgery and in some cases may extend post-amputation/grafting survival times by several months (mean survival times of 9 - 18 months have been reported). Both these agents are expensive and have potentially harmful side effects. In practice they are usually quite well tolerated by healthy dogs but they do require careful administration and monitoring of the patient.

RADIATION may palliate the pain and temporarily delay the progression of the primary tumour but in our experience radiation is only truly beneficial in less than 50% of cases, and then only for a short period of time (usually about 6 months). Radiation is not advisable in cases where the tumor has destroyed greater than 50% of cortical bone, because there is a very high risk of pathological fracture in such cases. Radiation also seems to be of little value in dogs which are not able to bear weight on the limb prior to therapy.

PALLIATION in the absence of an effective treatment for these devastating tumors many owners chose to use pain-killing (anti-inflammatory / analgesic) drugs to relieve the local discomfort caused by the tumor, until such time that they feel the animal's quality of life is compromised. At this point euthanasia is the humane course of action.

PLEASE HELP US WITH THIS IMPORTANT STUDY

Further information and study forms may be obtained from :

Dr. Jane Dobson - Department of Clinical Veterinary Medicine - University of Cambridge - Madingley Road - Cambridge - CB3 0ES - UK

or

Angela McInnes - Gatehouse Cottage - Calow Green - Chesterfield - Derbyshire - S44 5XQ - UK

Tel : +44 (0)1246 - 209323

or by email from : mailto:Morvern@aol.com