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

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Mast cell tumor treatment: surgery and radiation

We’ve spent a number of recent blogs understanding how MCT behave, how to confirm the diagnosis, MCT grade, what staging tests to consider, and what the prognostic predictors are. Now let’s talk treatment.

First, let’s think about the three main conventional tools oncologist use to treat tumors: surgery, radiation, and chemotherapy.

In general, it is best to think about surgery and radiation as local treatment options. By “local”, I mean dealing with the primary tumor: we either remove the cells with surgery or irreparably damage them with radiation.

On the other hand, chemotherapy is systemic therapy. It is given orally or intravenously (into a vein) and the drug circulates through the body systems. In general, chemotherapy is not the treatment of choice for the primary tumor. Instead, it is usually recommended as a follow up treatment for a primary tumor that is at high risk of metastasis, or spreading through the system to other organs.

Let’s more specifically look at using surgery and radiation therapy to treat MCT —  and I’ll save chemotherapy for another post.

Surgery

Surgery is the treatment of choice for MCT, and often the only treatment needed. The goal is to completely excise (remove) it and prevent its recurrence. The surgeon should aim for a minimum margin of two centimeters all the way around the tumor, including at least one deeper tissue layer. Then, a surgical biopsy must be submitted to the lab to determine the tumor’s grade, and to determine whether the margins are complete.

What if the tumor is too large for surgery?

This may be the case with large tumors on the legs, face, but also on the body trunk. In those cases, I might try to shrink the tumor before the surgery, so that we can then remove it more easily. For this, I use chemotherapy or radiation treatments.

What if the surgical margins are narrow (less than 2 cm), or dirty (have detectable cancer cells)?

If the scar is in an area of the body that can handle a second surgery, I recommend a scar revision — second surgery — to remove more tissue. The reason for this is that a completely removed tumor is less likely to recur at the surgical site.

For some MCT, especially those located on the lower leg, surgery alone may not achieve the necessary clean and wide margins, because there just wasn’t sufficient tissue surrounding the tumor. In these cases, radiation therapy will almost always be recommended.

Radiation therapy

If there are microscopic cells remaining after surgery, a follow up with radiation treatment provides excellent long term local control. The vast majority (85% to 95%) of dogs with low- or intermediate-grade MCT remain tumor-free two to five years after radiation treatment. Even high grade MCT cases can benefit: in a recent study, 70% of dogs with grade III MCT were still alive one year after radiation treatment.

Remember, radiation, like surgery, only treats the primary tumor site (that’s why we call it a local treatment) — it doesn’t prevent metastasis.  The radiation is typically directed to the area three centimeters around the surgical scar to prevent recurrence, and is usually scheduled two to three weeks after surgery.

Radiation instead of surgery?

Using radiation after surgery is helpful, but radiation therapy is less successful as a primary treatment for a measurable tumor. Only 50% of dogs were still alive after one year in one study. If radiation is being considered as a primary treatment, it is often helpful to add chemotherapy and steroids for an improved outcome. I consider this a palliative approach for non-resectable, or inoperable, tumors. Radiation therapy may also effectively shrink an inoperable tumor, which may allow more complete removal of the remaining tumor in a future surgery.

In the next blog, we will discuss the systemic treatment option for MCT: chemotherapy. Remember, there is more in the Guide in addition to non-conventional approaches to supplement your dog’s care, including supplements, nutrition, and diet.

About the Author: Susan Ettinger, DVM, Dip. ACVIM (Oncology)


Susan Ettinger, DVM. Dip. ACVIM (Oncology) is a veterinarian oncologist at Animal Specialty Center in New York and the co-author of Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog's Life Quality and Longevity. She blogs about dog cancer at http://www.DogCancerBlog.com.

  • Connie Bennett

    My beautiful 7yr old Shar Pei Buck just passed away Tuesday morning 10/30/12 from MCT Stage 4 iwas told! He had it on his muzzle & it could not be removed! My Vet put him on Prednisone & said it was the best treatment! On 8/28/12 we had a Biopsy down which came back as MCT. 2 months later he was gone, it was in his lymph nodes, he was all swollen on each side of his neck the size of two tennis balls! A chest X ray at the time of the biopsy showed no sign it had spread to his lungs. I feel like the prednisone was just not the best treatment, but I trusted my Vet of 27 years. I can’t bring my precious baby back, but I wish I had gotten a second opinion!

    • Dr. Susan Ettinger

      Connie,
      I am so sorry about Buck. Try to focus on the good memories of all the times shared through the years. Thinking of you during this difficult time.
      With sympathy, Dr Sue

  • ingrid

    I’m so sorry for your loss Connie, my white German Shepherd named Duce passed away last yr. 1 week before Thanksgiving, and my other female Shepherd CC passed the day before Thanksgiving , Duce had lymphoma and was put on steroids and he died soon after:( CC had the same thing she was very old, strange cause she was fine and they go to the vet regularly. Its like they didn’t want to be without one another and she developed the same thing.

  • Nancy

    Our (mostly) lab had an intermediate grade MCT removed in April and it was quite large. The vet was wonderful; she got what appeared to be all of the tumor on his side/abdomen during surgery plus at least 2 cm – in some spots, she said 3 cm. The lab tests came back, in fact as cancer. No other treatment was necessary after the surgery she said, so we came back 6 months later (last Friday) and he’s now what we consider a cancer survivor, for sure! So your comment “Surgery is the treatment of choice for MCT, and often the only treatment needed” seems to be true, so far in our case. Keeping fingers crossed! Thank you for a wonderful, insightful blog.

    • Dr. Susan Ettinger

      Nancy,
      Great news for your lab. Keep up with the monitoring and rechecks! I am so happy you are enjoying the blogs!
      All my best, Dr Sue

  • Janine

    I have got to say that i truly believe most vets are wonderful, but what i found when i took my beautiful 15 year old lab Chloe to our vet of 15 years for a lump on her hind leg (which turned out to be a soft tissue sarcoma) was that he didn’t have a sense of urgency, he was very familiar with us, he wanted to see how it was in 2 weeks. With hindsight i felt that he was assuming that perhaps we wouldn’t pay the big bills. I very much regret that i did wait 2 weeks and when i went back he wanted to wait again, he wasn’t being proactive so that was when i got a second opinion and things started happening in terms of treatment. Chloe has gone to God now and i am a bit wiser now and won’t hesitate to advocate for my other dog who is going through the same issue, thankfully with a much better prognosis. I believe our long standing former vet is very competent, I also believe that i was to passive. I now have a lot more knowledge thanks to The Dog Cancer Survival Guide. Thanks.

    • Dr. Susan Ettinger

      Janine,
      I am sorry to hear about Chloe. I am glad the Guide has help. Thinking of you.
      With sympathy, Dr Sue

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  • sharon hill

    Hi Janine,

    We had the same situation happen to us. After waiting months we finally had our dogs tumor removed from her front elbow and it came back as a grade 3 soft tissue sarcoma. The surgery did not succeed in clean margins. We are trying to decide to go ahead with radiation and chemo (not something we want to put our babe through) or just go with radiation and hope that it does not spread too quickly to her lungs. We are also toying with the option of doing nothing and giving her the best for the time she has left. (she is 11 years old) We see another oncologist tomorrow and will find out exactly what the options are.

    Did you go through any treatment with your sweet Chloe? To be honest, we are simply at a loss as to which direction to go………

    How is your other doggy doing? Thinking of you!

    Sharon

  • Kirby maragulia

    My 4 year old beagle is currently recovering from surgery to remove a MCT. We are waiting for the biopsy but he had X-rays, all of the blood work and Buffy coat and ultrasounds and the cancer has not spread. I want to start him on supplements ASAP, but the vet discovered in the ultrasound that our dog only had 1 kidney! Because of this do you see any reason that the supplements would be harmful?

  • Julie B.

    I lost my sweet 2-yr. old yellow labrador boy 2 yrs ago in March. He had a grade-3 Mass Cell tumor..I am still devastated & think what I could have done differently? The fact that he was so young, makes it that more tragic too. It started off as a little irritation on his back (we thought it was a tick bite at the time.) Brought him to the vet & they took the puffed up tick out & said he was fine. The area got more infected as time went on. I brought him back in & they didn’t know what it was..they treated it like a simple infection. These were supposed to be the best vets in the area (we were new to the area.) I’ve done alot of research after he was diagnosed & even I would think to ask about mast tomors. I should have asked them to biopsy it in the beginning to see what it was..they didn’t offer that & they acted clueless. Until it got too big & was an open sore, did they say it had to be removed & biopsied, then gave me the grave news that there was no hope! I tried alternative therapies with a holistic vet, but at that time, he was diagnosed with 2 months to live & he barely made that. We have a new lab & I have him on a grain-free diet & feed him lots of things with antioxidants. I h ave no idea what caused my poor pups Cancer..I woudln’t wish that on anyone!! :(

    • Dr. Susan Ettinger

      Julie,
      I am so sorry about your lab. Even as an oncologist who loves my job because I get to help pets with cancer and their families, cancer sucks!
      I am so sorry for all your went through!
      With sympathy, Dr Sue

  • Bailey’s Mom

    I just found your blog and have been absorbing the info…. started looking up feeding a dog on prednisone. My 11 year old Staffy “Bailey” has had 2 surgeries to remove MCT. Her prognosis was under 4 mos the Stage is III and the mitotic index of 25 (yes, 25!). She also had a amalenotic malenoma removed (after the 2nd removal of MCT) from her lower mandible. This was found when going in to have stiches removed after 2nd surgery. We are trying to decide weather to proceed with Chemo or just continue with the prednisone/pepcid/benadryl which I know is for paliative care. We can’t financially make a long term commitment to chemo (maybe 2-3 mos). Will that do more harm than good and would we just be prolonging the innevitable and have the situation only worsen? I know its hard to predict as each dog is going to react differently (or so we’ve been told)… I’ve purchased your book tonight but need to make the decision about moving fwd with chemo soon as we already had blood and biochem workup so the cost is 1/2 what it would be if we wait another week (at least for first month). I don’t need to go into how devistated my husband and I are. We didn’t have kids and all our maternal and paternal instincts have been poured into her the last 11 yrs – some think we’re crazy, but we don’t care. We’ve spent over $3,000.00 since December but are at a crossroads we know we don’t have a great deal of time and just want her to be comfortable. I’d go broke if I thought we could cure her but that’s not an option. I don’t want her to be here longer just to make me feel better. I wish she could talk to me – and sometimes I know she tries! We lost my mother-in-law last July to lung cancer and my husband doesn’t want to see our little girl suffer like his mom did from the chemo. Any advise you can offer would be so appreciated! Thank you and God Bless you.