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Bone Cancer
Introduction Symptoms Prognosis Treatment
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Summary
This info sheet
kindly provided by M J Brearley MA VetMB MSc(Clin Onc) FRCVS
Bone
tumours in dogs
Introduction
Bone tumours tend to affect the larger and giant breeds
more than small dogs. Irish Wolfhounds, Great Danes,
Rottweilers and German Shepherd dogs appear to be at
particular risk. To date, no familial or genetic factors
have been identified although it has been postulated that
the growth characteristics of the at-risk breeds are
important. The tumours tend to arise in the limb bones
with the most active growth plates i.e. distal radius,
proximal humerus, distal femur, proximal tibia and distal
tibia. The combination of the relatively rapid growth and
the weight of the individual is implicated. (See The Dog's
Skeleton for information
on the canine skeleton).
Symptoms
Middle-aged dogs are more commonly affected and the first
clinical sign that is noticed is either sudden onset
lameness or a swelling at one of the characteristic
sites. Bone tumours can be intensely painful, so much so
that the dog can be severely affected by this and
lameness, inappetence, 'grumpy' and generally poorly are
common signs. As the tumour grows, the swelling and
lameness increase and routine painkillers give little or
no relief. Obviously not all sudden lameness and
swellings are bone tumours - joint injuries such as
sprains or ruptured ligaments can also cause the clinical
signs. Veterinary attention should be sought at an early
stage in all cases.
The majority of bone tumours are of the type known as
osteosarcoma - this is a malignant tumour arising from
the bone cells themselves. Other tumours include
fibrosarcoma (tumour arising from fibrous tissue),
chondrosarcoma (cartilage origin), and haemangiosarcoma
(blood vessel tumour). Whilst x-rays can be used to
detect a bone tumour, laboratory examination of a biopsy
is necessary to determine the exact nature of the
problem.
Prognosis
The prognosis for any bone tumour has to be grave.
Without treatment, the primary tumour will become so
painful that euthanasia will be the only option. Almost
all bone tumours of the legs are malignant (cancerous)
and therefore have the potential to spread. Most tumours
of the bone will have spread long before the primary
tumour is first noticed. Therefore, even when the primary
tumour is cured the secondary tumours eventually grow to
such a size that severe breathlessness and general
malaise become over-whelming.
Treatment options
There is no simple treatment for bone tumours in dogs. It
is a very serious disease and therefore requires
aggressive therapy to achieve any chance of success.
However in recent years, progress has been made:
Analgesics
either with drugs or by radiotherapy to the
primary site. The pain relief achieved by
radiotherapy tends to be better and of longer
duration than by drugs but even so the pain is
likely to start up again within the next 6 - 9
months. However, not all bone tumours are
suitable for radiotherapy as destructive tumours
are likely to fracture. Radiotherapy has no
effect against the secondaries.
Limb
salvage by removal of the affected bone and
replacing this with a bony graft, a large metal
plate and fusion of joint. This option is fraught
with complications and even in the best hands
there is a 30% - 40% failure rate.
Amputation
is the only certain way of controlling the pain
and primary tumour problem. Most dogs will cope
very well with amputation including Rottweilers
and Great Danes with the loss of a forelimb. The
pain associated with the primary tumour is often
so severe that the dog is walking on three legs,
if they can manage at this stage they will be so
much happier and pain-free without that leg.
Anti-cancer
drugs can be used as an additional treatment with
the last two options (ie: limb salvage and
amputation) to control the rate at which
secondaries develop. Following removal of the
primary tumour by whatever means, but without use
of drugs, 60% of dogs will develop secondaries
(and have been put to sleep) by six months and
only 1 in 10 survive to one year. With the use of
chemotherapy (carboplatin infusion) the six
months survival is about 60%, with 4 in 10 alive
at one-year survival and about 20% alive at two
years. Earlier diagnosis and more aggressive
treatments may improve on this. Carboplatin
treatment is not without its occasional problems;
some nausea and vomiting may occur after the
treatment but this usually resolves within a
couple of days. Currently the drug is
administered once every 3 weeks for three doses.
Summary
Bone tumours in dogs tend to affect the large and giant
breeds. They are almost always malignant and secondary
spread is a serious problem. Treatment is directed
against the severe pain of the primary and amputation
offers the best control - most large dogs can cope
extremely well on three legs. Chemotherapy can slow down
the rate at which secondaries grow and about 15 to 20% of
dogs with osteosarcoma can now be cured. Further research
and new drugs will help improve on this in the future.
If you have any further questions about bone
cancer or any other aspect of cancer in dogs you should
speak to your veterinary surgeon who will be able to
discuss this with you more fully.
If you are concerned about the health of your pet you
should contact your veterinary surgeon.
See also http://www.vetspecialists.co.uk/Information
sheets/canine_osteosarcoma.htm
M J Brearley MA VetMB
MSc(Clin Onc) FRCVS
RCVS Specialist in Veterinary Oncology
Manor Farm Business Park, Higham Gobion,
Hitchin, Herts, SG5 3HR
Tel: 01582 883950 Fax: 01582 883946
Veterinary Radiology Ltd Regd in England 3058672
www.vetspecialists.co.uk
This page last updated 24 March 2002
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