Once you have been told the horrible news that your dog has been diagnosed with cancer, so many thoughts start racing around your head. One of the common questions I get is, “How long will my dog live, Doc?”
Despite all my training and experience as an oncologist, this is so hard to answer.
During my residency training I had to learn lots of numbers and statistics related to a cancer. I’ve discussed some of the common terms in a previous post, The Oncologist’s Perspective on Statistics: Part Three. In that post I discuss median survival times, response rates, metastasis rates. These are important facts to learn about for your dog’s cancer.
How does treatment impact how long your dog will live — and how likely is he to respond to that treatment?
How high is the metastasis rate?
These are very complicated questions for an oncologist to answer. For example, for a low or intermediate grade soft tissue sarcoma (STS), incomplete surgical margins (aka “dirty”), make recurrence (the tumor regrowing in that same area) 10X more likely, and so additional surgery or post-op radiation is recommended if there is a recurrence. BUT … with low or intermediate STS, the metastasis rate (how often that tumor spreads to other areas of the body) is 10-15%, so chemotherapy, which treats the entire body, is not typically recommended. In contrast, let’s look at a high grade STS. For these tumors, the metastasis rate climbs up to 40% — so chemo may be recommended to delay metastasis.
That’s a lot of numbers to juggle, and if you’re a little confused, it’s because it’s confusing. And then there is this:
Numbers Are Just Numbers — Not Your Dog!
I’ve blogged before about how stats are helpful, but don’t predict the way individual cases turn out in that series on statistics, but I bring it up again because my cases this week drove this home, both good and bad.
Case: Osteosarcoma in Blackie’s Wrist
Blackie is a mixed breed dog with osteosarcoma (OSA) of his left metacarpal bone. This is one of the bones in the paw just below the wrist (carpus).
I met Blackie after his front leg amputation, and we reviewed all the stats for OSA. Osteosarcoma is the most common bone tumor — 85% of dogs with cancer in the bone will be diagnosed with osteosarcoma.
Statistics tell us that three-quarters of these tumors develop in the limbs, with the front legs twice as likely develop this tumor. The most common locations are towards the knee and away from the elbow – the top of the shoulder, the wrist, and the knee (bottom of femur or top of tibia). The metacarpal location is less common but it is reported.
Here are those numbers, or stats: survival times for OSA cases with amputation and no other treatment is about four to five months, with 90-100% dying by one year, and only 2% still alive at two years. In contrast, the median survival times for OSA cases with amputation and chemotherapy increase to ten to twelve months, with 20-25% of dogs are still alive at two years.
We also discussed that chemotherapy is well tolerated. 80% of dogs that receive chemo have no side effects. About 15-20% have side effects and most are mild and self-limiting — they recover on their own with little intervention – maybe some nausea and/or diarrhea, which is treated at home with meds or antibiotics. 5% or less are severe and may lead to hospitalization.
So back to Blackie. He had 3 doses of chemo, with very little side effects, but when he came in for his 4th treatment, he was not doing well. His legs were swollen and he was reluctant to walk. His right front leg was most significantly swollen, and considering he only has 3 legs, I was very concerned.
My training made me suspicious he had developed lung mets (metastasis) and a very uncommon condition related to that called HO, or hypertrophic osteopathy, which is when new bone develops along the shafts of long bones. HO is most commonly seen with metastatic disease to the lungs, especially OSA. Blackie’s chest X-rays confirmed the metastasis. Plus he had a skin met near his thigh and another met deeper under his skin by his right humerus.
This was only 3 months after his amputation! I took a few deep breaths before I went in the room to tell his dad that the statistics I gave him at the initial appointment had not predicted poor Blackie at all. His tumor has turned out to be way more aggressive than the statistics would have led us to believe. This week, we need to shift gears to make him more comfortable and see if we can slow the progression of the mets with a new therapy.
Case: Daisy Mae’s Splenic Osteosarcoma
The other case I saw this week where the stats were less than helpful was Daisy Mae. You can see her picture on my Dr. Sue Facebook page – she’s pretty darn cute!)
Daisy Mae was diagnosed with OSA of her spleen, called extraskeletal OSA (because it is outside the skeleton). It’s an uncommon tumor in the spleen (hemangiosarcoma and benign hemangiomas are more common). There’s limited data in the literature. In one report, the median survival time with surgery alone was 1 month, and 5 months with surgery plus chemotherapy.
After surgery, we decided to give Daisy Mae conventional IV chemo followed by anti-angiogenic oral chemo. This week she is 18 months out and tumor free at her checkup! I always say I love when I am “wrong”, and my patients outlive the stats.
Bottom Line: Use the Stats, Don’t Live By Them
So should you ignore statistics and published studies? Of course not! They can help you to make treatment decisions.
But you must realize that stats will never predict the individual. I personally hope your pet outlives the stats, but my advice — after all my training and years of clinical experience — is this:
Learn the facts, and then be hopeful.
Live longer, live well,