Updated: Jul 14
As a vet, dealing with canine cancers is likely going to be a significant part of your job. Another significant part of that job is dealing with the owners of dogs with cancer. Those owners can be anything from resigned to distraught, and many of the most desperate pet owners seek out anything they can think of to help improve the prognosis of their precious pet.
As recent years have shown in stark lighting, medical misinformation is pervasive and preys upon the desperate. Whether it's Ivermectin for Covid, the latest trend of crystal healing or herbal remedies, or old snake oil, the desperate and vulnerable will seek out anything they can to augment – or in some cases, replace – traditional medical treatments.
In some ways, it's even worse for animal medicine. Since veterinary medical treatment often lags behind human medical advances – and since it covers such a wide variety of animals – information can get muddled and confused. Something that works for cats or birds or horses won't work for dogs, but people who read a paper summary might lack that nuance. It's fertile ground for scammers and profiteers to hook the hopeful and desperate.
Therefore, part of a vet's job is knowing what works and what doesn't, and where to draw the line. Even if explaining this can be very difficult to people who don't want to hear the truth, it has to be done.
So, where does Arginine fall into this discussion?
What is Arginine?
Arginine is one of the essential amino acids found in the food most living things eat. For people, it's conditionally essential – some synthesis can occur, but much of what we get comes from our diets. For dogs and cats, arginine is not synthesized, meaning they have to get all of their dietary allotment from their food.
Dogs require a specific amount of arginine to remain healthy.
"Puppies fed an arginine deficient diet containing adequate total protein will experience a decreased food intake and hyperammonemia resulting in vomiting and ptyalism, with an increase in urinary orotic acid excretion and muscle tremors. There are also reports of puppies developing cataracts after being fed an arginine-free milk replacer. Feeding an arginine deficient diet to adult dogs results in a decreased food intake." - Wikivet.
To wrap back around to the discussion at the beginning, nutrition is a critical aspect of care, but it's also a vector for a lot of health misinformation and "treatments" that can be ineffective or, worse, actively hinder real treatment.
"To be blunt: In the hands of an expert, nutrition can save your dog's life. In the hands of an amateur, nutrition could end it." – Whole Dog Journal.
It's not uncommon for a pet owner to find dietary information to supplement or even replace more traditional – and more expensive – treatments. Whether they ask about special diets, supplements, or just the option of arginine adjustments, it's something that's bound to come up sooner or later. Knowing how it interacts with healthy cells is part of the puzzle.
Arginine is used in a variety of ways, but one such way is in the cellular replication and repair cycle.
In healthy cells, a cyclical lifespan eventually leads to a phase where the cell works to repair its DNA and replicate itself into additional healthy cells. Arginine is a fuel for this process.
Cancer cells are essentially damaged cells that replicate uncontrollably, with damaged DNA, causing tumors and other problems. Depending on the kind of cancer, they may build up in one place as a localized tumor, or they may spread into many, but in both cases, the cancer cells require nutrients to replicate just like normal healthy cells. They tend to replicate faster and with fewer checks on their behavior than healthy cells, however.
How Arginine Interacts with Cancer
If cancer cells require arginine to replicate, and arginine must be delivered through the diet, surely a way to hinder the spread of cancer would be to limit dietary arginine intake, right?
This is true in some situations. Arginine deprivation can shut down cancer cells permanently. They try to replicate, fail to do so, and starve while waiting.
Healthy cells do this, too, except instead of starving, they shut down and go into stasis. When arginine is reintroduced into the system, healthy cells can wake up and return to their function. Cancer cells, however, do not revitalize.
"This is especially true of lymphoma cells. It takes three days of arginine deprivation to shut down the growth of canine lymphoma cells. Canine osteosarcoma (bone and connective tissue cancer) cells shut down permanently after six days of arginine deprivation." – Canine Biologics.
Arginine deprivation is hard on a dog, though. As described above, arginine deprivation can lead to organ damage, cellular shutdown, and other issues. Extended deprivation can lead to death in extreme cases.
This is not to say that arginine deprivation does not have a potential place to accentuate treatment. However, it must be carefully controlled.
Furthermore, all of this is dependent on the type of cancer. Some cancers respond to arginine deprivation, others to excess arginine.
"Arginine does not always stop the growth of cancer. It can do the opposite. Arginine-induced growth has actually been used to good effect in an experiment where researchers were trying to put more cancer cells in the S-phase, where they would be more readily killed by a certain chemotherapeutic drug. (Under normal circumstances, however, enhancing growth is obviously not desirable.)
Research shows that at least one pancreatic cancer cell line is arginine-dependent. And other studies show that if arginine is given at a certain phase of cancer development, it can promote, rather than block, growth." – Life Extension.
Knowing what you're dealing with is just part of the puzzle.
Arginine and Chemotherapy
Chemotherapy follows a variety of different protocols with different drugs meant to treat different cancers along different pathways. In broad strokes, it all works in roughly the same way. Chemotherapy drugs are, essentially, a form of poison that kills off the cells that take it in. Both healthy cells and cancerous cells will take in a chemotherapy drug.
Chemotherapy is effective because cancer cells are voracious and take in nutrients (and chemotherapy drugs) much more rapidly than other kinds of cells do. The drug may kill healthy cells, but it kills cancerous cells much more quickly and thoroughly because those cells are absorbing the bulk of the drugs.
Arginine deprivation would hinder this process by hindering the cancer cells' ability to replicate. Thus arginine is important for chemotherapy. Arginine essentially "revs up" cancer cells into taking in more of the chemotherapy drugs, making it broadly more effective.
As chemo helps kill cancer cells, the dog's natural immune system can then catch up to the cancer and help get rid of it. This may put the dog into remission and can even be curative, or it may be less effective. One of the challenges of cancer is that it's often individualized enough that results are difficult to predict.
Of course, nothing is simple, even with something like arginine. Biology loves to be as complex as possible, with a million moving parts. One example relevant to this discussion is arginase. Arginase treatments augment the restriction of arginine to make it even more effective at treating lymphoma and osteosarcoma. However, this has barely been studied and isn't necessarily a treatment you can easily recommend.
There's always more to the discussion of cancer, and there always will be until such time as treatments for each different cancer are discovered.
To Feed or Not To Feed
A critical decision you need to make as a vet offering a treatment plan for cancer in a dog is, what do you recommend as the best course of treatment?
Obviously, there are established standards for many cancers. Cancer is a pervasive issue, has been well studied, and while advances are being made every year, established treatment plans have proven results and can often offer the best broad-spectrum option for pet owners. Whether it's something old and established like prednisone or a more recently-developed treatment like STELFONTA, the variety of options available requires extensive knowledge to sift through.
Arginine presents a unique discussion point. Arginine itself is not a treatment for cancer. On its own, it does not prevent cancer – indeed, it facilitates its growth. Restricting arginine can be effective at hindering certain cancers, like lymphoma and osteosarcoma, but other cancers don't respond the same way, or the damage done to the dog would be worse than the damage done to the cancer.
The first thing you need to know, then, is whether or not restricting arginine is a good idea for a given patient's cancer. If it is, you have to know how long the restriction should last before the dog requires the nutrients it needs to survive.
On the other hand, if a restriction is not in order, supplementation might be. Arginine, given in addition to what is found in a standard diet, might be beneficial in augmenting the ability of chemotherapy drugs to invade and destroy cancer cells.
This is even more important because many cancer treatments – and the other side effects of cancer on dogs – can lead to a dog not eating as much as they normally would. Supplementation helps encourage at least a baseline level of arginine in the diet, even when appetites are short.
Now consider this decision for each individual dog while taking into account their age, the staging of the cancer, and more. Then consider that every different cancer will respond differently to different treatments. It's a lot to keep in mind!
Your Options as a Vet
As a vet, this is a lot to keep in mind. Even canine oncology specialists have a ton to remember, and it's all they do, day in and day out. General practice vets, vet techs, veterinary nurses, and vets with other specialties have virtually no chance to be familiar with all of the options off the top of their heads.
Essentially, you have a small handful of options.
Option one is to work with an oncologist. Each time a patient is brought in and diagnosed with a canine cancer, they can be referred to the oncologist partner, and you can move on to other patients. This helps lighten your workload while ensuring that your patients are in the right hands when they have questions and need treatment. You do, of course, need to know a reasonably local oncologist who will work with you, though. With the ongoing vet shortage, this is increasingly difficult.
The second option is to memorize the options for a handful of common cancers and hand anything else off on referral. Lymphoma, for example, is a very common cancer in dogs, so learning what treatments are most effective – and what considerations they may have, like stringency in timing, viability across breeds, and the expenses on the pet owner – can give you a working knowledge that is effective enough. This can work, though it can have the drawback of feeling like you aren't doing as much as you wish you could.
The third option is to contact us. At Hope Vet, our panel of experts is standing by to help you out with the complex cases you aren't equipped to handle on your own. No single veterinarian can know everything, and it's better for you to have a strong base of general knowledge and a network of connections for specialty situations than it is to try to know everything and burn out in the process.
At Hope Vet, we're ready and willing to consult with you on cases such as:
Complex internal medicine cases
Emergency and critical care
When a problem crops up, and you don't have the knowledge to handle it, you can contact us and use ours. Together, we can provide the best options and outcomes for your patients.
Don't forget to take time for yourself as well. Vets across the country consult our panel of experts to ease their workload and improve their mental health.
For both kinds of assistance, all you need to do is reach out to get started! If you have any questions about how it all works, we're more than happy to answer them as well.