Samarium Treatment

Palliative treatment of Canine Osteosarcoma using Samarium-153 Osteosarcoma is a malignant disease of bone often seen in large and giant breed canines. Unfortunately it has a very poor prognosis because approximately 90% of dogs with osteosarcoma are thought to have micro-metastatic disease at the time of diagnosis. Therefore the main goal of treatment is to relieve the pain associated with the tumour and, if possible, slow down the progression of the primary tumour and metastatic disease.

A promising option for canine osteosarcoma that we offer at the Gladesville Veterinary Nuclear Centre is treatment using Samarium 153. It is important to note that there are several “treatment” options available for osteosarcoma and the final decision should be based on each individual case such as: size, general health, degree of lameness, cancer sites and other medical problems of the dog.

Samarium-153 is a “bone-seeking” radio-isotope which emits both gamma and beta rays. The dual radiation characteristic of Samarium is important in that the gamma ray activity allows the use of scintigraphy to track uptake of the radioisotope and the beta ray activity gives it the ability to cause localised tissue destruction.

When injected in conjunction with a bone-seeking pharmaceutical, it is selectively taken up by rapidly metabolising bone cells as are found in steosarcoma. Thus at a cellular level a dose of radiation is given to the tumour itself.

Use in human medicine Samarium has most often been used in human patients for treatment of painful bone metastases from malignancies such as rostatic and breast carcinoma.

It has been shown to reduce the requirement for analgesics in these patients and is considered to be an effective palliative measure to relieve pain.

Generally, pain relief has occurred within one week of administration.

Use in Canine Osteosarcoma

There have been several studies done to determine the overall effectiveness of this treatment, but the evidence is mounting that Samarium is capable of providing good pain relief and slowing the progression of the disease.

In patients where the tumour was localized within the skull or mandible, Samarium can actually be curative. In a study that evaluated 15 dogs with Osteosarcoma, the median survival time for dogs receiving Samarium was 5 months compared to 1-2 months for dogs receiving no therapy.(1) This positive effect on survival was likely due to increased time to metastasis and a slowing of the tumour growth, which was noted radiographically.

Importantly, pain relief was evaluated as well. More than half of the dogs experienced some pain relief and five of the dogs were assessed to be pain-free after treatment.

Frequently asked questions

When can I have my dog treated with Samarium?

Samarium is generally obtained from the Lucas Heights nuclear reactor here in Sydney, however it must be ordered in advance and is only available once a fortnight. We will need to check the next availability date when you ring to make an appointment.

What can I expect when my dog is being treated with Samarium?

After a consultation here at Gladesville Veterinary Hospital the dog, if a suitable candidate, will be admitted to hospital for treatment with Samarium.

The actual procedure is quite fast, the dog is sedated and given an intravenous injection containing the Samarium. Depending upon the situation, the dog may be then scanned using the gamma camera to determine the amount and distribution of uptake. Once the imaging is complete, the dog will then spend the next 4 – 5 days at our nuclear ward whilst the radioactivity level declines. The rate of decline is based on the half life of Samarium-153.

Elimination of any Samarium-153 not taken up by bone is through the urine and faeces. We are specially equipped here at the Gladesville Veterinary Nuclear Centre to deal with radioactive patients and waste products. The dogs are monitored twice daily and measured with a Geiger counter to determine when they safely can be sent home based on government standards. The dogs are still slightly radioactive for a few days and we advise owners not to have prolonged close (less than 1metre) contact with the dogs for another 4 days and to discourage them from having the dog share the bed or couch.

How many treatments will my dog require?

Each dog will vary. Our general recommendation is that if the dog shows a clinical response to the first dose it should be treated repeatedly when the bone marrow has recovered as determined by blood tests. This is approximately every 6-8 weeks.

What aftercare is required post treatment?

A complete blood test should be performed by the referring Veterinarian two weeks after treatment. In addition, the dog should be closely monitored for any signs of illness or primary bleeding disorder as they will low white blood cells and platelets after treatment. If the dog shows any sign of illness in this 2 week period Veterinary advice should be sought immediately.

What is the cost for a treatment of Samarium?

As at April 2013 the cost is approximately $4000 which includes a consultation with Professor Max Zuber and 4 days in our Nuclear Medicine Ward. Cost will vary from case to case.