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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Why Test For Heartworm But Not Cancer?

Updated: January 20th, 2020

I was recently thinking about a little problem us veterinary professionals are faced with.

We seem to have forgotten about relative risks.

A relative risk is simply the risk of something in comparison to something else.  Take the risk of cancer versus the risk of heartworm in a dog on heartworm preventative.

Now, I am a practicing veterinarian and I do annual heartworm tests on my patients.  Granted, I live in an area that has one of the highest heartworm rates in the country. However, guess how many heartworm positive dogs I diagnose in patients receiving their heartworm preventative?

Almost zero. I think I had one case in my career, maybe two.  I have over 5000 canine patients registered at my hospital. That’s pretty low odds.

Okay, let’s switch it up.  How about how many patients do I see with cancer?  A lot.  Cancer is the number one pathological killer of dogs today, with mortality higher than trauma, diabetes, kidney disease and any other disease state.

Depending on who you believe, somewhere between one in four to one in six dogs will die of cancer.

Clearly there is something wrong with this picture.  Why is the public accepting of annual heartworm tests and unaware of cancer as a threat?  Why are dog lovers not demanding that every lump and bump be checked?

What about blood work,  urinalysis, X-ray and ultrasound for the internal cancers?

One argument is cost.  A heartworm test is $40-60 dollars.  The screens I mentioned for internal cancers are crude and costly. But, they are what we have.

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So, how would one test for internal cancer, in a way that make sense?  Well, it is tough to test for each internal cancer, since there are many types.

There is a specific cancer test for lymphosarcoma made by Pet-Screen, which is in England.  Your vet can contact them and arrange for sample processing, although it is not cheap. So that’s one, and they are working on a hemangiosarcoma test next.

And the fact is that our cure rate for truly malignant cancers is quite low these days, so it would seem that we need a slightly different approach. When we diagnose cancer currently, we are late in the game.

Carcinogens, family traits, free radical excess, viruses, and more alter healthy genes, turning them into cancer-causing genes.

Testing for these altered genes that set up cancer is going to be quite complex and costly.  There are many of them and they are not clarified yet.  Sure, we are aware of gene sites of mutations leading to cancers like ras, erk, trk, myc, the b proteins, and the huge family of the protein kinases, among others.

The problem is that the number of these genes quite high, so I believe it makes less sense to test for the mutations leading to cancer.

There are other factors, aside from damaged genes, that are responsible for cancer development.  These include metabolic abnormalities, many involving sugar.

In addition to abnormal metabolism setting the stage, we have factors creating immune system suppression.

For more helpful tools and information, get a copy of the Dog Cancer Survival Guide

And a major one, I believe perhaps the biggy, is inflammation in the body, and the chemical signals that are tied to it.

Ongoing chemical signals in inflammation increase free radicals (which promote mutations), suppress the immune system, and are tied to metabolism problems that promote cancer growth.

One of the central genes involved in inflammation is called NF-kB.

If this gene is being turned on over abnormally long periods, you have lots of inflammation. This is not healthy at all.

Why not test for excessive, prolonged NF-kb signaling?  This could help screen for increased risks for cancer development.  Many cancers make a lot of NF-kb. There are other health risks seen when this gene is turned on excessively that a dog’s guardian would want to know about.

On top of that, we could be proactive much earlier, perhaps even before detectable cancer development.  One could be more vigilant, begin antioxidants, cut the carbs, begin anti inflammatory supplements, eliminate body fat, and then reassess.

We could also start our cancer hunt earlier and more aggressively in these dogs.

Yes, this is just one idea and requires a lot of work. Yet it is a candidate for a cost-effective way to take action when it really counts,  possibly before cancer starts. You heard it here first, folks.

Take home message?

Focus on catching cancer early. For the time being you will have to settle for blood testing, X-ray, ultrasound, urine testing, and checking every growth on your dog. And don’t forget the Pet Screen lymphosarcoma test.


Dr D

Leave a Comment

  1. Ethel Christensen on March 26, 2020 at 1:32 am

    I live in Omaha ne, my rottweiler was just diagnosed with lymphoma, he’s only about 5 maybe 6
    He came to me with heartworms 2 years ago, be was treated successfully, he’s not overweight, I don’t use chemicals in my yard, my vet says due ti the Corvid19 chemo isn’t an option right now!
    Not sure I would put him through chemo anyway, close friend going through that right now, horrible!
    But is there anything else I can di for him? This is so sudden, he was just sty the vets in February for his last heartworm test, no swollen lymphoid than. He’s on prednisone swelling went down, but his neck had golf ball size! I’m just so frustrated, could the treatment for heartworm cause this cancer?
    What can I do for Remy?

    • Dog Cancer Vet Team on March 26, 2020 at 7:51 am

      Hello Ethel,

      Thanks for writing and we’re sorry to hear about your boy. As we’re not veterinarians, we can’t offer you medical advice. But we can point you towards the information in Dr. Dressler’s writing 🙂

      As Dr. D writes in the Dog Cancer Survival Guide, there are a number of things that you can do to help your dog with cancer ( with your vet’s supervision). Conventional treatments (chemo, surgery, or radiation), Nutraceuticals, Immune Boosters and Anti-metastatics, Diet, and Mind-Body strategies. This is what he calls Full Spectrum Cancer Care, which you can learn about, here:

      In general, Dr. D also recommends the Dog Cancer Diet for most dogs with cancer. He does write that it will need to be modified to suit your dog’s particular needs. Here’s the link where you can download a free copy of the diet:

      We hope this helps! 🙂

      Sending warm wishes to you and your boy!

  2. LisaT on March 27, 2011 at 1:00 pm

    I heard today from a couple that had their GSD tested for hemangiosarcoma using a brand new blood test that is out. I’m wondering if there is any info about it on this site, though I’m off to google…

  3. Gerard on July 19, 2009 at 7:09 am

    There is a blood test for the early detection of canine cancer – developed by Biocurex, Inc. It is a Universal Cancer Biomarker

    • Dr. Dressler on July 19, 2009 at 7:14 am

      I there is no information available on this under construction website. Since this is a new test, I am interested to find out the details!!

  4. Dr. Dressler on June 21, 2009 at 11:05 am

    Great thought. Sadly, the AMAS test has not been applied to dogs with cancer, nor do those stats hold up for humans in 3rd party analysis:

    “CONCLUSIONS: The AMAS test discriminates suspicious and malignant from benign lesions, but sensitivity is insufficient to identify patients to be spared biopsy and false-positive rates are too high for population screening.”

    Here is the link for you to check out for yourself:


  5. Sheila Aumiller on June 19, 2009 at 4:37 pm

    Having had cancer myself, I researched a lot to see what to eat and not eat, to stay healthy and cancer-free as long as God would permit. I have learned that SOY can be harmful (with certain types of cancer)…. mine, for instance. I therefore make an effort now to see that my precious dog does not have SOY in her food. Whilst living in the USA, I know SOY is in almost everything on the Supermarket shelves. I read every small label! When we move back to the UK, very soon, I don’t believe there will be such a problem, as SOY is not used so widely over there… but I will still check carefully to see that my girl does not have that ingredient in her diet – as with mine. I welcome the time that it is made common knowledge to the public that SOY can be harmful to many of us at risk.

  6. Susan Lauer on June 19, 2009 at 6:48 am

    Dr. Dressler, will this not work on dogs?

    There is now a blood test that will accurately detect early cancer of all types. It has an accuracy of greater than 95%. If the test is repeated, the accuracy is greater than 99%. That is to say, that false positive and false negative rates are less than 1%. The test is called AMAS.

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