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

Mast cell tumor treatment: chemotherapy

Updated: June 2nd, 2020

In my last blog, I discussed surgery and radiation for MCT. Today we will focus on chemotherapy.

Which dogs need chemo?

Your dog may not even need chemotherapy. In many dogs that I see with MCT, I do not recommend chemotherapy at all. This is because chemotherapy is not as effective as surgery and radiation for treating the primary tumor, especially if the cancer is of a lower grade and/or confined to one local area.

The exception to this is when I use chemotherapy (instead of radiation) for large MCT tumors which need to be shrunk prior to surgical removal. I also consider palliative chemotherapy for non-resectable (inoperable) tumors, if radiation therapy is not available in your area, or if you have decided against radiation.

If I’m worried about metastasis, I may recommend chemotherapy in addition to surgery and radiation. This is most common for grade III MCT, which is prone to metastasize.

In addition, I sometimes also use chemotherapy for grade II MCT with high proliferation marker scores or for multiple skin MCTs. Some of these cases are complicated, so I decide this on a case-by-case basis. Remember, these are not one size fits all tumors, so consult with a specialist to decide on the best options for YOUR dog.

Commonly used drugs include vinblastine, prednisone, Lomustine, and the new tyrosine kinase inhibitors, Palladia and masitinib (Kinavet CA-1). You can read more about all these drugs in the chemotherapy chapter in the Guide, but let’s talk about the new class of drugs called tyrosine kinase inhibitors (TKI), Palladia and Kinavet.

One-third of dogs with MCT have a genetic mutation in the c-Kit gene that leads to a cellular protein called tyrosine kinase to be stuck in the “on” position. This stimulates tumor growth and leads to increased survival for mast cell tumors.

The TKI drugs, Palladia and Kinavet target this genetic mutation specifically. They work in two ways to fight MCT: cut off blood supply to MCT by blocking angiogenesis, and inhibit tyrosine kinase. Because the drug targets the protein and blood vessel receptors, it is considered “targeted therapy.”

Both Palladia and Kinavet are available in the U.S. and are FDA-approved specifically for dogs with recurrent, Grade II and Grade III MCT, with or without regional lymph node involvement.

When do I use the TKIs?  I think they are important tools for dogs with the c-kit mutation, recurrent tumors, inoperable tumors, and can even be considered for incompletely resected MCT. I know in my previous blog, I recommended radiation after surgery to prevent recurrence, but the way TKIs inhibit blood vessels (anti-angiogenesis) make them an alternative for preventing recurrence as well. We still need more studies on this approach.  Because complete responses with many of the MCT drugs are uncommon, I often use the TKIs in combination protocols.

Overall, these are relatively new drugs, and I’m excited about its results both in clinical studies and in my patients.  Like all chemotherapy drugs, there is the potential for side effects with TKIs. I personally find them well-tolerated in my patients. In my practice, I work with Guardians to monitor them closely, adjust the protocol as needed, and maintain a great quality of life while taking the medication.  Don’t be scared of these drugs. It helps to find a specialist with a lot of experience using these. Not every dog needs chemotherapy including the TKIs.

Additional Considerations for Mast Cell Tumors

In addition to surgery and radiation, and possibly chemotherapy, you may want to consider supportive medications to counteract the effects of possible degranulation (when the mast cell tumor breaks open). The following are especially helpful for dogs with large tumors, detectable spread, and systemic signs such as vomiting: anti-histamines (such as Benadryl), antacids (such as Pepcid) and proton pump inhibitors (such as Prilosec). These can often be stopped after surgery, if the tumor has been successfully removed and spread has not occurred; some dogs may need these drugs long-term to control their symptoms.

Finally don’t forget the “non-conventional” approaches like Apocaps as discussed in the Guide.

Leave a Comment

  1. Natalie Lucia on April 1, 2013 at 6:41 am

    My 13 year old Siberian has had a grade 3 mass cell tumor removed from her chest . 2-4 mitotic rate no c-kit . geisha is full of energy and her appetite is normal . She has been on prednisone and vinablastine . The margins were 1cm to 1.5 cm clean . I have been reading about radiation . It has been 5 weeks since the tumor was removed . Would she benefit from radiation treatment ? Please help I am so tormented. Thank you Natalie

    • Dr. Demian Dressler on April 10, 2013 at 6:25 pm

      Hi Natalie,
      how big was the mass? This can help to answer the question. Radiation is a way of trying to kill cancer cells around the surgical scar that were left….and larger tumors require bigger excisions…so its a bit hard to say without more info.
      I would definitely be treating your dog systemically though as grade 3 often can be life threatening, although there can be exceptions.
      For the time being, maybe these blogs will help:
      there are also a whole series of posts about mast cell tumors on this site- just use the tool bar search function.
      I hope this helps
      Dr D

  2. Sue Forkenbrock on February 10, 2013 at 9:28 am

    My Australian Shepherd, Scully, has mast-cell tumors and has been operated on
    twice. She is facing a third surgery. I was wondering if there is anything else I
    could do for her. Is there an oral medication that will help fight the cancer? She
    eats Barking at the Moon dog food and drinks tap water. Could these be
    contributors to her cancer? She is 13, but otherwise in excellent health. Please
    help me help her!


    Sue F.

  3. Amber on February 7, 2013 at 5:06 am

    One of my dogs Mia was diagnosed with MCT and she recently had surgery to remove it. The removal surgery was sucessful and the dr reported that he was able to remove the entire tumor and worked slowly during her surgery to ensure that he removed it all and also saved her thyroid which was in the area of the tumor. All of her blood work has been great she has had no problems I wouldn’t know she had cancer if I didn’t find the lump and have it tested. Since her surgery she has had to have fluid drained from the incision site and now it looks as if there is still a lump where the tumor was removed which I am so concerned about. The dr who is not the surgeon said that it is scar tissue, but why does it still look like a tumor is there if it was removed? Also the surgeon recommended chemo just to ensure that it doesn’t come back or spread and stated that with MCT chemo is normal follow up after a tumor removal. I don’t have the money to do chemo I am still paying off the surgery so I am trying to do everything else I can. If chemo is just used to follow up to try to keep from reoccurance is it really necessary. Also is it normal for some dogs to not want the dog cancer diet at first?

  4. Pam on January 23, 2013 at 4:41 pm

    Hi, we have a cat that has been diagnosed with cancer and the vet suggested Tyrosine kinase inhibitor therapy (Masitinib or Palladia)..Do you work with cats or just dogs.,..

    Thank you..

    • Dr. Susan Ettinger on February 3, 2013 at 12:03 pm

      These TKIs have been used in cats, but it is “off-label” meaning these drugs were developed in dogs. Still they can be considered in cats. Discuss with your oncologist. Good luck,
      All my best, Dr Sue

  5. Elaine on November 20, 2012 at 7:11 pm

    We have seen good results with essential oil Tsuga and Frankincense pure therapeutic oils applied topically to MCT. We also recommend tumeric, fish oil and the anticancer diets (Budwig type)

  6. K. lawrence on November 6, 2012 at 9:15 am


    • Dr. Susan Ettinger on November 24, 2012 at 4:39 pm

      Thanks for the suggestion. I will try to get the osteosarcoma soon in the future. There is also a chapter on this on the Guide.
      All my best, Dr Sue

  7. K. lawrence on November 6, 2012 at 9:13 am

    Please discuss the latest treatments for osteoscarma .

  8. Bill on November 6, 2012 at 7:46 am

    Our Dog Chelsea has a MCT on her lip. It is too risky of an operation to go that way. Our oncologist is recommending Palladia and radiation – she says there are some postive studies on this. What are your thoughts?

    • Dr. Susan Ettinger on November 24, 2012 at 4:38 pm

      Bill, if surgery is not an option for the MCT, radiation and chemotherapy are good alternatives. In some cases, these treatments may shrink the tumor enough for the mass to be surgical. Good luck!
      All my best, Dr Sue

  9. Elaine Claar on November 6, 2012 at 3:57 am

    Our three year old Boxer, Spike was on Kinavet for a year following removal of a recurring MCT on his head. He is now off the Kinavet for FOUR months with no sign of the tumor returning! He’s running and playing and shows no sign of the cancer. Thank you so much for this article. As I was researching Kinavet and Palladia, I had a hard time finding any information on the drugs. I want everyone reading your blog to hear Spike’s story!! 🙂

    • Dr. Susan Ettinger on November 24, 2012 at 4:35 pm

      Such wonderful news that Spike is doing well. Love it when dogs with cancer are living longer and living WELL.
      All my best, Dr Sue

  10. Rod on November 6, 2012 at 2:26 am

    You write: “Finally don’t forget the “non-conventional” approaches like Apocaps as discussed in the Guide.” — What are those non-conventional approaches?

    • Dr. Susan Ettinger on November 24, 2012 at 4:31 pm

      Hi Rod,
      Our book, The Dog Cancer Survival Guide, does into detail about supplement including Apocaps, diet, immune system boosters, and brain chemistry modifications. I hope you find it helpful, and thanks for reading!
      All my best, Dr Sue

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