My dog was diagnosed with osteosarcoma yesterday. What are…

Hello there , I am DrD.I will try my best to answer your questions.I am sorry to hear you and your dog is going through this.It is my understanding that the biopsy and chest x ray results are not in yet. Osteosarcoma can develop in any bone but the limbs account for 75-85% of affected bones. Osteosarcoma of the limbs is called appendicular osteosarcoma. It develops deep within the bone and becomes progressively more painful as it grows outward and the bone is destroyed from the inside out. The lameness goes from intermittent to constant over 1 to 3 months. Obvious swelling becomes evident as the tumor grows and normal bone is replaced by tumorous bone.

The location and radiographic appearance of the osteosarcoma in the limb are quite classic but there are a few outside possibilities that should at least be mentioned. There are only a few other possible conditions that cause lytic lesions in bone: the chondrosarcoma, or the squamous cell carcinoma, or the synovial cell sarcoma or fungal bone infection.

So let's wait until we get the biopsy results.Keep in mind that dogs are usually euthanized due to the pain in the affected bone. Treating the pain successfully will allow a dog to live comfortably.Amputation of the affected bone is recommended for any tumor involving bone. When the malignant structure has been removed, it is submitted for biopsy and the diagnosis confirmed at that time. Biopsy before amputation is felt to simply add a painful procedure and, if possible, is reserved for tissue already amputated.Removal of the affected limb resolves the pain in 100% of cases. Unfortunately, many people are reluctant to have this procedure performed due to misconceptions.Median survival time for dogs who do not receive chemotherapy for osteosarcoma is 4 to 5 months from the time of diagnosis regardless of whether or not they have amputation.

Osteosarcoma is unfortunately a fast-spreading tumor. By the time the tumor is found in the limb, it is considered to have already spread. Osteosarcoma spreads to the lung in a malignant process called metastasis. Prognosis is substantially worse if the tumor spread is actually visible on chest radiographs, so if chemotherapy is being considered, it is important to have chest radiographs taken.

• Chemotherapy is the only meaningful way to alter the course of this cancer.
• Young dogs with osteosarcoma tend to have shorter survival times and more aggressive disease than older dogs with osteosarcoma.
• Elevations of alkaline phosphatase, one of the enzymes screened on a basic blood panel, bode poorly. These dogs have approximately 50% of the survival times quoted below for each protocol.
• The presence of tumor in lymph nodes local to the leg being amputated also bodes poorly. In the study by Hillers et. al published in the April 15th, 2005 issue of the Journal of the AVMA, median survival was significantly longer (318 days vs. 59 days) in dogs where the tumor was not evident in local lymph nodes at the time of amputation.

Radiotherapy for Pain Control
Radiation doses can be applied to the tumor in three doses (the first two doses should be given 1 week apart, the second two doses 2 weeks apart.) Improved limb function is usually evident within the first 3 weeks and typically lasts 4 months (many oncologists report a range of 0 to 19 months.) When pain returns, radiation can be re-administered for further pain relief if deemed appropriate based on the stage of the cancer at that time.

• When pain is relieved in the tumorous limb, there is an increase in activity that can lead to a pathologic fracture of the bone.
  
• Radiotherapy does not produce a helpful response in about one-third of patients. (Remember, amputation controls pain in 100% of cases but if amputation is simply not an option, there is a two out of three chance that radiotherapy will control the pain.)

Drugs
At this time there are numerous analgesic medications available for dogs with this tumor. No single medication, however, is a match for the pain involved in what amounts to a slowly exploding bone. A combination of medications is needed to be reasonably palliative and should be considered only as a last resort if amputation or radiation therapy will not be pursued. There are several types of drugs that can be combined.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
These are anti-inflammatory pain relievers developed for dogs: carprofen, etodolac, deracoxib, meloxicam, firocoxib, and tepoxalin. These are typically given once or twice daily in tablet form at home. The patient should have good liver and kidney function in order to take medications of this class.

Bisphosphonates
This class of drug has become the standard of care in humans with bone tumors yet bisphosphonates have not become a common part of veterinary practice for this condition. Bisphosphonates act by inhibiting bone destruction, which in turn helps control the pain and bone damage caused by the bone tumor. The most common bisphosphonate in use for dogs is pamidronate, which is given as an IV drip over two hours in the hospital every 3 to 4 weeks. In humans, an assortment of potential side effects have emerged (fever, muscle pain, nausea all lasting 1 to 2 days in up to 25% of patients, renal disease in certain situations, low blood calcium levels, jaw bone cell death); these issues so far have not panned out as problems for dogs and cats. Because bisphosphonate seem to be well tolerated, relatively inexpensive, and useful in numerous bone-destroying cancers, we expect to see this class of drug used more and more in small animal practice.

Narcotic Pain Relievers
While these drugs do not have anti-inflammatory properties, they are well-known analgesics and have been used in an assortment of forms for thousands of years. They are particularly useful in chronic pain because they do not interact negatively with other pain relievers. Drowsiness is a potential side effect. Tramadolhas been particularly popular as part of a drug combination for bone cancer pain but there are other narcotics that might also be considered.

Miscellaneous Supplemental Pain Relievers
There are two drugs that have surfaced as additional pain relievers for animals with chronic pain: gabapentin and amantadine. Gabapentinworks on neurologic pain and is rapidly surfacing in the treatment of arthritis, surgical pain, and other chronic pain states. Amantadineworks by reducing what is called wind up, a phenomenon where nerves become sensitized to pain leading to the experience of pain from stimuli that normally do not cause pain.

These different drugs are often given together to create meaningful pain relief to the osteosarcoma patient when amputation and radiotherapy are not going to happen.

How do we Treat the Cancer?

Osteosarcoma is unfortunately a fast-spreading tumor. By the time the tumor is found in the limb, it is considered to have already spread. Osteosarcoma spreads to the lung in a malignant process called metastasis. Prognosis is substantially worse if the tumor spread is actually visible on chest radiographs, so if chemotherapy is being considered, it is important to have chest radiographs taken.

• Chemotherapy is the only meaningful way to alter the course of this cancer.
• Young dogs with osteosarcoma tend to have shorter survival times and more aggressive disease than older dogs with osteosarcoma.
• Elevations of alkaline phosphatase, one of the enzymes screened on a basic blood panel, bode poorly. These dogs have approximately 50% of the survival times quoted below for each protocol.
• The presence of tumor in lymph nodes local to the leg being amputated also bodes poorly. In the study by Hillers et. al published in the April 15th, 2005 issue of the Journal of the AVMA, median survival was significantly longer (318 days vs. 59 days) in dogs where the tumor was not evident in local lymph nodes at the time of amputation.

Cisplatin (given IV every 3 to 4 weeks for 3 treatments)

• The median survival time with this therapy is 400 days.
• Survival at 1 year: 30% to 60%
• Survival at 2 years: 7% to 21%
• Giving less than 3 doses does not increase survival time (i.e., if one can only afford one or two treatments, it is not worth the expense of therapy)
• Cisplatin can be toxic to the kidneys and should not be used in animals with pre-existing kidney disease.

Carboplatin (given by IV every 3 to 4 weeks for 4 treatments)

• Similar statistics to cisplatin but carboplatin is not toxic to the kidneys and can be used if the patient has pre-existing kidney disease.
• Carboplatin is substantially more expensive than cisplatin.

Doxorubicin (given IV every 2 weeks for 5 treatments)

• The median survival time is 365 days.
• 10% still alive at 2 years.
• Toxic to the heart. An ultrasound examination is needed prior to using this drug as it should not be given to patients with reduced heart contracting ability.

Doxorubicin and Cisplatin in Combination (both given IV together every 3 weeks for four treatments)

• 48% survival at 1 year
• 30% survival at 2 years
• 16% survival at 3 years.

What Exactly is “Median” Survival Time?

When a population is evaluated statistically, there are a number of ways the central tendency of the group can be evaluated. The median is the value at which 50% of the group falls above and 50% of the group falls below. This is a little different from the average of the group, though more people are familiar with this term. When you evaluate median survival times, you are looking at a 50% chance of surviving longer than the median (and a 50% chance of surviving less than the median).

What Does Chemotherapy Put my Dog Through?

Most people have an image of the chemotherapy patient either through experience or the media and this image typically includes lots of weakness, nausea, and hair loss. In fact, the animal experience in chemotherapy is not nearly as dramatic. After the pet has a treatment, you should expect 1 to 2 days of lethargy and nausea. This is often substantially palliated with medications like Zofran® (a strong antinausea drug commonly used in chemotherapy patients). These side effects are worse if a combination of drugs is used but the pet is typically back to normal by the third day after treatment.

Effectively, you are trading 8 days of sickness for 6 to 12 months of quality life. Hair loss is not a feature of animal chemotherapy.

As far as the cost , this could depend what is going to be done.Nonsteroidal pain killers with narcotic pain killers and new pain management drugs like Amantidine, Gabapentin would help If no radiation theraphy and surgery is not an option. Please do not hesitate to ask if you have more questions.All the best. DrD.