Canine Osteosarcoma – Our Experience Part II
Today I want to cover Maggie’s diagnosis and the first phase of her treatment.
As I mentioned in Part I of our series on Osteosarcoma, Becca was diagnosed with OSA based on her xrays. They displayed what is a typical “sunburst” pattern in her shoulder. Her vet eventually performed a needle aspirate of the tumor and confirmed the diagnosis during her first radiation treatment. This image is not Becca’s xray, but it does demonstrate what hers looked like and the sunburst pattern they talk about as it relates to OSA.
Maggie’s diagnosis was not as easy to confirm. Our regular vet and the radiologist they consulted were uncertain whether what they saw in the xray was OSA or possibly something else. He convinced us to run a series of fungal tests on Maggie in order to rule out another cause. While we waited for the results – they took five days – we went ahead and made an appointment with a veterinary oncologist. He reviewed Maggie’s xrays and felt certain OSA was the only explanation. That is one thing that I would recommend if you get a diagnosis of OSA or any type of cancer – if there is any question, see a specialist. Their level of knowledge and expertise can’t be matched. It’s the same with human ailments – much as I might like my GP, if I’m diagnosed with cancer or a heart condition – I’m getting a 2nd opinion and treatment from a specialist.
Normal diagnostic tools used by veterinarians for OSA would begin with xrays of the affected limb. As I mentioned above, there is a typical pattern to be seen, that starburst pattern. If it’s obvious, it’s a fairly straightforward diagnosis. Your vet may run a series of other neurological and orthopedic test to rule out other potential causes of lameness – just as we did with the fungal tests.
If a definitive diagnosis cannot be made from the xrays, a bone biopsy is likely to confirm it. There is always the chance of a false positive, but with both our Becca and Maggie it was confirmed with the bone aspirate.
From diagnosis, you move on to treatment options. Given the aggressive nature of OSA, this should be done as quickly as possible. We made the decision to move forward with our treatment option the same day the Oncologist made his diagnosis. There is no time to waste.
The most common treatment for OSA is amputation of the affected limb. This is a curative measure – you are removing the tumor. It also offers the best survival times for your dog. Care will be taken to examine your dog for metastasis of the tumor. Additional xrays of the lungs and possibly ultrasound of the abdominal and lymph nodes may be recommended to rule out obvious spread of the cancer. If tumors are apparent in other bones, or in the lungs, the amputation may not be recommended and purely palliative (pain relief) care suggested. If amputation is indicated, it is likely your vet will suggest supplemental chemotherapy as there is likely micrometastasis of the tumor already as we noted in our first post.
The decision whether amputation is a viable option depends on a number of factors: the location of the tumor, the age and condition of your dog, and most important, the quality of life they may have after the amputation. Neither Becca or Maggie were considered good candidates. Becca’s tumor was in her shoulder and she had multiple orthopedic issues including a fused spine. Maggie’s tumor is a bit lower in her leg, but she also has severe arthritis in her opposite leg. They were both seniors. Our vets felt removal of the leg would have impacted their mobility negatively and their quality of life been greatly reduced and recommended alternatives.
The other common treatment for OSA, if amputation is not viable, focuses on palliative measures – treatments designed to alleviate the pain of the tumor. For Becca, we opted with radiation treatment of her shoulder and chemotherapy. The radiation would not cure the tumor, but it is designed to slow the growth and thereby help with pain relief. The chemo was designed to limit or kill the cancer spreading to her other organs. Becca responded well to the radiation and her limp improved and she regained some strength. Unfortunately, she had a negative reaction to the chemo regime and became quite sick. We stopped the medication immediately, but Becca lived only a few more weeks. You can read more of her story here.
Radiation treatment is administered in multiple doses over a period of time. Since the radiation is designed to attack the DNA of cells and it doesn’t discern between cancerous cells and healthy cells, care must be taken to minimize the damage to healthy tissue surrounding the tumor. That’s why it is administered in small doses, over time, to allow for recovery and reduce potential damage.
Maggie’s vet offered us a newer, innovative treatment only introduced for dogs in the last several years. The treatment is a specialized form of radiation therapy called Stereotactic RadioSurgery (SRS) or CyberKnife radiation. It has been used to treat humans for many years. The benefits of this treatment over regular radiation is the ability to isolate the tumor from health bone and concentrate heavy doses of the radiation on the tumor alone – thereby stopping it’s growth and potentially eliminating it without harming the healthy tissue around it. Because of the high concentration of the delivery, it can be administered in more frequent sessions, so treatment time is accelerated. Accurate mapping of the tumor in order to isolate it from healthy bone is done immediately preceding the SRS using a CT Scan. Maggie is sedated for the treatment, but the full procedure lasts only about an hour, so she is only very lightly sedated.
In addition to the radiation, the vet recommended a dosage of Pamidronate, a bone strengthener designed to strengthen her bones and help defend against a pathogenic fracture.
There are several different chemotherapy protocols that may be administered to address OSA. Your vet will determine which drug or combination is most suitable for your pet. I don’t recall the exact protocol of Chemotherapy given to Becca. I do remember she received Carboplatin, but I believe she was given something else too. I think Becca’s age and overall condition impacted her ability to handle the chemo and that contributed to her body’s bad reaction. Maggie is younger and her overall physical condition much better than Becca’s and I’m hoping, if we decide to also treat her with chemo that she will handle it better.
It’s wise to read up on the drugs, their side effects to be aware of what to look for in your pet’s reaction and what you can do to alleviate any discomfort. I’ve provided some links below that I found helpful.
Maggie finished her SRS treatment on August 19th and we had our one-week follow-up on the 28th. She is doing quite well and is eating & sleeping normally. Her limp is gone and she is back to enjoying her daily walks and games. Our vet recommended we begin to cut back on her pains meds as she was on the max doses, so we started that and so far so good. We met with the Medical Oncologist yesterday to discuss chemotherapy treatments. I’ll cover more about that in our next installment. Stay tuned.
Osteosarcoma (bone cancer)
Treatment targets canine cancer
CyberKnife RadioSurgery in Pets
Stereotactic Radiation Therapy
Osteosarcoma in dogs – current treatment protocols
Cancer & Chemotherapy