The Dog Cancer Survival Guide (101 page)

As we’ve discussed, microscopic lesions – micrometastasis – are present in 90% of dogs with OSA. While chest CT scans can sometimes pick up these smaller lesions, the test requires anesthesia and is expensive. Also, current treatment recommendations and prognoses are based on results of chest X-rays, not CT scans, so if small and early metastasis is detected on CT, its effects on prognosis and survival are not known. Even if metastasis is not found, I recommend proceeding as if metastasis were likely and chemotherapy necessary.

Full blood panels, including a CBC and chemistry panel, should be run, and a urinalysis performed. Regional lymph nodes should be aspirated or biopsied to check for metastasis, even if they appear to be normal. Although lymph node spread is uncommon (occurring in fewer than 5% of dogs), its presence is a negative prognostic factor; treated dogs that also have lymph node involvement live only two months, compared to eleven months for those without. Knowing whether OSA has spread to the lymph nodes can help you make treatment decisions. (Make sure that your vet or surgeon requests the lymph node evaluation when submitting the amputation, because these are not routinely evaluated at all labs.)

Tumors spreading to other bones are the second most common site of metastasis, so if there are signs of pain or lameness in another area of the body, regional X-rays should be taken to look for lesions. I do not typically recommend whole body X-rays, because of the added cost (it takes a lot of X-rays in a big dog to get this done) and the overall low probability that a dog has bone metastasis at diagnosis (about 6%). However, when a dog is lame or hurting in more than one secondary area, whole body X-rays can be considered.

In a few cases, nuclear bone scans can be helpful, although they are not widely available and there is some conflict over their usefulness, because they detect any active bone growth. Growth can, of course, be bone metastasis, and it may also be evidence of osteoarthritis or infection. If a positive site is found on a nuclear bone scan, a bone biopsy will still be required to make an accurate diagnosis.

Although metastasis to the abdominal organs is uncommon, I still recommend an abdominal ultrasound for dogs confirmed for or suspected of OSA. It’s not painful or invasive, and it can be used to evaluate the dog’s overall state of health, before embarking on extensive and expensive treatments.

I provide a staging system for other cancers in this book, usually based on the World Health Organization’s (WHO) official system. Unfortunately, the WHO’s human-based staging system is not particularly useful for OSA, because most dogs are already in an advanced stage when we discover the cancer. For this reason, I have chosen not to include it.

In general, OSA is a fast-moving, aggressive dog cancer, with 95% eventually metastasizing. Without treatment, most dogs with OSA are euthanized within two months because of progressive pain, poor quality of life, a pathologic fracture, or the possibility of one.

Dogs treated with amputation alone have a median survival time of four to five months, with at least 90% succumbing by one year and only 2% surviving to two years.

Dogs treated with amputation
and
chemotherapy experience a lengthened median survival time of ten months to one year, with 20-25% of dogs still alive at two years.

Clearly, dogs who receive amputation and chemotherapy experience a better prognosis. There are also other well-established and reliable predictors to help you determine your dog’s prognosis.

Dogs with smaller tumors; dogs with no lung, bone or lymph node metastasis at the time of diagnosis; dogs with normal alkaline phosphatase (ALP) levels and dogs whose biopsies indicate a low grade of cancer, all have a better prognosis.

A dog whose ALP level returns to normal within forty days of surgery has a better prognosis than a dog whose levels remain elevated.

Dogs who undergo limb-spare procedures (techniques which are designed to avoid amputation)
and
are treated with antibiotics for infections at the surgical site, actually experience improved survival rates. This is likely due to the activation of immune cells and their response to stimulated inflammatory chemicals.

Conventional treatment for OSA targets the primary tumor with local treatment (surgery and/or radiation) and targets the likely micrometastasis with systemic treatment (chemotherapy).

The main goal of local treatment is to prevent recurrence and control the pain that dogs inevitably feel with OSA. Amputation, as radical as it may sound, is usually the best treatment option. The complete removal of the affected limb prevents a possibly sudden and painful fracture and effectively removes the source of deep, aching bone pain.

If it is hard for you to contemplate amputation, you are not alone – most owners simply cannot imagine how their dogs could live a good life without all four limbs. It’s important to know that they are usually happy after having made the choice to amputate. Dogs typically adapt very well to the loss of a limb and can still run, play and even swim. Many dogs have already started bearing more weight on the unaffected limbs, so their recovery time post-amputation is often just a few days. You can purchase a harness or sling a towel under his belly to assist your dog during recovery.

Amputation is not right for every dog. Dogs with very severe arthritis and some neurological conditions may not be able to walk well after an amputation; older dogs with average, moderate arthritis, usually do well on three legs. In any case, it is worth checking the opposing limb carefully to make sure it seems capable of bearing the added weight. It’s also worth noting that lesions confined to the scapula can often be removed by just removing the scapula, not the whole leg.

For dogs whose owners are reluctant to amputate, and for dogs with pre-existing conditions that preclude amputation, a limb-sparing procedure might be a good approach. These procedures vary, depending upon the case, and usually involve removing only the affected bone and then replacing it with a bone from a donor, or from the patient, himself (in these cases, the cancerous bone is removed, radiated with high doses, and replaced). The new implant should be plated and fused, which may not be possible in every location; the ends of the radius and ulna bones at the wrist are the best locations for limb-sparing procedures. To be a candidate, your dog should have less than 50% of the bone involved in OSA, no fractures, minimal soft tissue involvement and a lesion that does not wrap around the whole bone.

Limb-sparing surgeries are more involved than amputations, more expensive and require a specialty hospital with the ability and experience to perform the advanced techniques involved. Survival times remain the same and these dogs have higher recurrence rates (20-30%). Limb-sparing techniques also do not address metastasis or micrometastasis, so chemotherapy is still needed for longer survival times.

Complications, including fractures and infections, are more likely to occur in limb-sparing surgeries than in amputations. These may require additional surgeries or even the very amputation that we were trying to avoid. As an interesting aside, dogs who develop infections are more likely to have overall successful surgeries and live longer – this is likely because the immune system’s response is strengthened by fighting the bacterial infection.

Some dogs are candidates for surgery to remove metastasized OSA lung tumors. When the primary tumor is under control and the metastasis is isolated and detected more than ten months after the original diagnosis, there is no other disease present, fewer than three or four metastatic lesions are visible and there are no new lesions after a month’s time, your dog may be a candidate for surgery. In one study, the mean survival time after lung metastasis surgery was six months, with a range of one month to four years.

Radiation therapy may also be used to treat OSA. The most common use is palliative intent therapy, which is aimed at reducing pain and increasing quality of life in dogs that do not get an amputation. The palliative protocol usually involves two to four once-per-week treatments. Radiation can reduce inflammation, lessen pain, improve the dog’s ability to walk and aid in the healing of micro-fractures. The majority of dogs do well on radiation: 75-90% experience good effects, usually after one or two treatments. For some dogs, these effects last only months, while for others they last over a year. During this time these dogs need less pain medication or no pain medications at all; the reason is not completely understood: it seems that radiation therapy releases pain-killing endorphins. Chemotherapy treatments given in addition to palliative radiation have been associated with better results, also.

The conventional treatments Dr. Ettinger recommends for osteosarcoma should be considered part of step one of Full Spectrum cancer care (
Chapter 11
). Please review that chapter for more general information about surgery, radiation and chemotherapy and how to handle their common side effects.

For more information on all other Full Spectrum steps, including nutraceuticals, immune boosters, dietary changes and brain chemistry modification strategies, review Full Spectrum cancer care, which begins on
page 103
.

You will also find information about specific chemotherapy agents in
Chapter 41
.

Radiosurgery can also be used as a limb-sparing technique – an alternative to the surgery described above – when amputation is not possible or not desirable. This is an advanced radiation therapy technique, available only at certain specialty hospitals (my hospital has the CyberKnife unit, which can focus high doses of radiation at very specific tumor sites with minimal radiation going to surrounding tissues). A CT scan is required to evaluate the extent of bone destruction from the OSA tumor and to carefully plan the radiosurgery, if it is indicated. Only one radiosurgery is required for limb OSA, and most dogs do well afterwards, with about 30% experiencing some form of complication. Complications depend upon the case (one is a bone fracture); the risk increases when the tumor has destroyed a lot of cortical bone (the very dense, hard outer shell of most bones). Radiosurgery is a fairly new technique; so far, the results at my hospital show that dogs receiving radiosurgery and chemotherapy to control metastasis have a median survival time of about one year, similar to the median survival time for dogs treated with amputation and chemotherapy. If you want to save your dog’s limb, you can afford radiosurgery, you can get to a hospital which offers it and your dog is a good candidate, this may be a good option to consider.

Surgery and radiation techniques offer local control of the primary OSA tumor (and sometimes of isolated metastasized tumors); local therapy is not enough to keep OSA metastasis at bay. Because most dogs (90%) have micrometastasis at the time of diagnosis and 95% of dogs will develop detectable metastasis, you should use a systemic therapy – in other words, chemotherapy. Without it, dogs without amputation live only two months and dogs with amputations live four to five months (median survival times).