L-Asparaginase: To Use or Not to Use

If your dog has been diagnosed with lymphoma, and you have chosen to pursue chemotherapy, then your vet may or may not have started out your dog’s treatment protocol with a drug called L-Asparaginase, or Elspar.  Originally the first drug given during the WI-Madison chemotherapy protocol (the most common protocol used for lymphoma), Elspar is now being removed from the initial round of chemo.  This has caused some concern among pet owners because this drug is known for rapidly attacking the cancer, often leading to dramatic results and a quick remission.

Why does this drug work so well and so fast?  First we have to understand the role that the amino acid asparagine plays in the body.  Asparagine is something that all cells need in order to produce protein.  However, cancer cells, especially lymphatic cancer cells, need huge amounts of this amino acid to survive and reproduce.  A typical healthy cell does not need much asparagine and can produce what it needs internally.  A cancer cell needs to rely on outside sources to feed itself.  That’s where L-Asparaginase comes in.

L-Asparaginase takes advantage of this situation by destroying any asparagine ouside of the cells, thereby cutting off the food source for the cancer cells. Within a short period of time, the cancer cells die off when they can no longer get enough asparagine to fuel themselves…resulting in those dramatic results and quick remissions. To the average pet guardian, Elspar often seems like a miracle drug that buys enough time for the other chemotherapy drugs to get to work.

So if Elspar works so well, why is it being removed from the original WI-Madison protocol?  According to Dr. David Vail at the UW-Madison School of Veterinary Medicine, several research studies have shown that using this drug at the begining of the protocol does not add to the length of the initial remission.  As a result, more and more vets are choosing to save Elspar as part of a rescue protocol, when the cancer cells start to become resistant to the original chemo drugs. 

So, if your vet suggests holding off on this valuable chemotherapy agent, it may actually be a good thing for your pup down the road.  If your vet does choose to administer this chemo drug early on though, they’re not necessarily wrong either.  Find out what their rationale is — being an active part of your dog’s treatment is essential throughout the process.  Don’t be shy about asking questions and expecting honest, clear answers.  Your first responsibility is to your dog and he or she is relying on you to be their voice and advocate during cancer treatment.  And, even the best vet can sometimes learn something new…even from one of their clients!


MacDonald VS, Thamm DH, Kurzman ID, Turek MM, Vail DM. Does L-asparaginase influence efficacy or toxicity when added to a standard CHOP protocol for dogs with lymphoma. J Vet Intern Med 19:732-736, 2005.

 Jeffreys AB, Knapp DW, Carlton WW, Thomas RM, Bonney PL, deGortari A, Lucroy MD. Influence of asparaginase on a combination chemotherapy protocol for canine multicentric lymphoma. J Am Animal Hosp Assoc. 41:221-226, 2005.

Piek CJ, Rutteman GR, Teske E. Evaluation of the results of a L-asparaginase-based continuous chemotherapy protocol in dogs with malignant lymphoma. Vet Quarterly  21:44-49, 1999.

Valerius KD, Ogilvie GK, Mallinckrodt CH, Getzy DM: Doxorubicin alone or in combination with asparaginase, followed by cyclophosphamide, vincristine, and prednisone for treatment of multicentirc lymphoma in dogs: 121 cases (1987-1995). J Am Vet Med Assoc 210:512-516, 1997. 



About Kerry Malak

I am a Bulldog mom, Reiki Master/Teacher, pet loss counselor and canine cancer advocate who loves working with people and animals to help them live longer, happier and healthier lives.
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5 Responses to L-Asparaginase: To Use or Not to Use

  1. Ran across this on Bing and I have to hand it to you, Tremendous Thanks!

  2. Lori Richards says:

    Thanks for the info. My beloved 21/2 years old Bulldog was very recently diagnosed with Lymphoma and just today has started on Chemo. The first drug of choice was Elspar. Hoping for the best with him. He’s a typical stubborn Bully. Hopefully his tough fighting spirit will shine throughout his 12 week treatment.

    • Kerry Malak says:

      Good luck to your sweet boy. It’s so unfair that he has cancer at such a young age. I hope he does great with treatment and has many more happy, healthy years with you.

  3. Helen says:

    My dog was diagnosed with nasal lymphoma which is actually very rare in dogs. The CHOP protocol induced a short remission. One discussion I had with my vet concerned his rationale for leaving out L-Spar from the initial induction. I am so glad that he did. My dog came out of remission and L-Spar is giving her a great quality of life .. for now.

  4. Helen says:

    correction: elspar

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