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Today I am going to talk about a case I saw last week, in the Oncology department
Elli is a 6 year old, female neutered Rottweiler who has had a long history of intermittent lameness on her left hindlimb, which has previously been responsive to non-steroidals. 2 weeks ago her owners other dog pushed her out the car and she landed heavily on her left hindlimb, however this time the pain was not responsive to analgesia She has been using the limb well when walking and running but is particularly stiff following a period of rest.
When she presented to us she was 3/5 lame on her left hindlimb We found a firm sweeling on the medial aspect of her distal left tibia. No other abnormalities were found on physical examination.
These are the investigations her referring vet had already performed All her haematology and biochemistry results were within normal parameters. 3 radiographic views had been taken of her thorax, but were non-diagnostic quality. A radiograph of her left distal tibia revealed this lesion, with osteolytic and proliferative areas and a poorly defined border.
A bone tumour was top of our differential list at this stage, with osteosarcoma being the most common We couldn’t rule out another primary tumour. Another possibility was that this was a bone metastases from another distant tumour. Another differential was a bone infection, with a bacterial cause being most likely in the UK
Osteosarcoma is the most common neoplasm affecting bones in dogs. It has certain predilection sites mainly at the metaphysis of long bones, particularly the proximal humerus, distal radius, distal femur and proximal tibia, so away from the elbow and towards the knee, although it can affect any site. The forelimb is more often affected than the hindlimb. 75% of osteosarcomas affect the appendicular skeleton, with the rest occurring in the axial skeleton. Mainly affected middle aged to older large breed dogs. The mean age is 7 years old, although it can affect any age. Rottweilers and st bernards are thought to have a genetic predisposition to developing osteosarcomas Elli’s signalment is typical of an osteosarcoma case as she is a 6 year old rottweiler Osteosarcomas are extremely locally invasive tumours and metastasise early in the disease process, mainly haematogenously. Micrometastases are present at the time of first diagnosis in most cases and most dogs die due to this metastatic disease within a year despite treatment.
The dogs present lame, this lameness is often severe and acute in onset but may be more chronic or may follow a traumatic incident Pain is due to microfractures or distruption of the periosteum induced by the osteolysis of the cortical bone A swelling is usually present at the primary site, which may be soft to firm and varies in how painful it is.
The first step in investigating a lameness where osteosarcoma is a differential is to radiograph the limb. Typically there are osteolytic and osteogenic changes, creating a ‘sunburst appearance’ Another classic characteristic is a ‘Codman’s triangle’ which is a trianglular deposition of dense new one at the periphery of the lesion, where the periosteum has been elevated. There is a long transition zone between normal and affected bone. Osteosarcomas do not cross joints Bilateral thoracic radiography is important as lungs are the most common site for lung metastases. Metastatic lesions are only visible when 6-8mm in size If the metastatic disease is visible, generally we would not pursue further treatment Abdominal ultrasound should be performed, as it is possible for osteosarcomas to metastasise to the abdomen. For a definitive diagnosis, a biopsy needs to be analysed. A core biopsy is obtained using a jamshidi needle. A biopsy is superior over an aspirate as it shows the architecture of the lesion.
At the SAH we performed a thoracic CT. This was due to the radiographs taken by the vet to be of non diagnostic quality A CT would detect earlier metastatic disease, but in Elli’s case no evidence of metastatic disease was seen.
An abdominal ultrasound scan was performed to check for any other metastatic disease. None were detected in the kidney, liver or spleen. The only abnormality seen was this prominent left mesenteric lymph node. This change is consistent with a mild reactive lymphadenopathy, but neoplastic infiltration could not be ruled out. However osteosarcomas do tend to spread haematogenously, not via the lymphatics We then took an aspirate of the lesion using a needle. We did this as there is a reduced risk of developing a pathological fracture and also we obtained the results a lot quicker than if we had taken a core biopsy The next working day we received the cytology results which supported our diagnosis of an osteosarcoma
There are many different treatment options available – the individual patient needs to be taken into consideration when chosing which is the most suitable option. Euthanasia is a valid treatment option if the owner does not widh or cannot afford treatment This is a terminal condition, associated with a lot of pain NSAIDs are a good option to provide analgesia, and COX2 inhibitors have been found to have some direct or indirect antitumour properties Bisphosphonates can also offer a substantial improvement in comfort levels and inhibit osteoclast activity. Radiotherapy achieved short to medium term analgesia in 70-90% of osteosarcoma patients Amputating the affected limb removes the primary lesion, so provides analgesia. Does not tend to extend survival times as metastatic disease still develops rapidly. Most dogs cope well with 3 legs, but it is important to make sure it is a suitable option on a case by case basis Limb salvage surgery is an alternative to amputation. There are various different methods, but mainly involve removing the primary lesion from the bone and replacing it with an allograft or metal plate Case selection is very important – suits early lesions of the distal radius best Animals take longer to recover than amputation, at least 4-6 weeks and complication rates are higher. Preferred over amputation if there is also neurological / orthopaedic disease As with amputation, survival rate is not improved unless add on chemotherapy Chemotherapy agents delay the development of significant metastatic disease. However it does not have much effect on the primary sarcoma as it is slowly dividing, so chemotherapy must be used as an adjunct to primary lesion removal. Cisplatin used to be used, however carboplatin (another platinum compund) has been found to have the same efficacy but with fewer side effects and is easier to administer as cisplatin required concurrent diuresis The main sign of carboplatin toxicity is myelosuppression, so a haematology profile should be checked before each administration Doxorubicin can also be used in the treatment of osteosarcomas, but studies have found carboplatin to be associated with longer survival times Although logically it may make sense to use these two types of chemotherapy drug (platinum compounds and doxorubicin) together, as they have different mechanisms of action, studies suggest survival time is not improved over using a single and the risk of toxicity increases
We gave Elli analgesia – choosing previcox and famotidine as she has had previous GI upsets associated with metacam Also as previcox is a COX-2 inhibitor, it may have antitumour effects and can work synergistican=lly with platinum compounds. Amputation of the left hindlimb is planned for next week She is a good candidate for amputation as it is a hindlimb, which dogs seem to cope better without compared to a forelimb. Also she is a very active dog so should cope well on 3 legs We will start her on a carboplatin protocol about 2 weeks after surgery, at around the time of stitches out as this will give the would a chance to heal first.
Unfortunately the prognosis is poor for Elli With palliative treatment the expected survival is 3-5 months With chemotherapy, this is increased to 11 months, with only around 30% surviving a year
Osteosarcoma is the most common bone tumour affecting dogs It should be considered in any forelimb lameness in adult large breed dogs There are many treatment options, but which are used should be decided on a case by case basis The treatment is not curative, as metastases develop so early on in the disease process
Elli the Rottie
Lucy Taylor – Grand Rounds
“Elli” – History and Presentation
6 year old FN Rottweiler.
Intermittently lame on left hindlimb for several months.
2 weeks ago fell out of car.
Pain unresponsive to analgesia.
Particularly stiff after rest.
“Elli” - Examination
3/5 lame on left hind.
Firm swelling left distal tibia
No other abnormalities
“Elli” - Investigations
All haematology and biochemistry
results within normal limits.
Radiography of the Lesion
Radiographs sent from the referring
veterinary surgeons non-diagnostic.
“Elli” – Differential Diagnoses
Chondrosarcoma, fibrosarcoma, liposarcoma
Commonly from mammary / prostatic tumours (unlikely in this
Osteosarcoma – Overview
Most common bone tumour in dogs (85%)
“Away from the elbow, towards the knee”
Middle aged and older large breeds
Osteosarcoma – History & Presentation
Often severe, acute onset
Pain due to microfractures
Swelling at the primary site
Treatment not curative
Take Home Messages - Osteosarcoma
Common bone tumour
Large breed dogs predisposed
Many treatment options
Choose on individual basis
Treatment not curative
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