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Mast Cell Tumor Treatments:

Pros and Cons for your Dog

What are Mast Cell Tumors in Dogs?

Mast Cell Tumors are one of the most common skin cancers in dogs.  They originate from mast cells, part of the immune system.  Read about mast cell tumors in detail. 

Treatment Options for Mast Cell Tumors

When your dog is diagnosed with a mast cell tumor, there are several treatment paths to consider.  Each option has benefits and limitations and the right choice often depends on factors like tumor grade, size, location and your dog’s health.  Read about the most common treatments so you can have an informed discussion with your veterinarian. 

Surgery
STELFONTA®
(tigilanol tiglate injection)
Chemotherapy
Radiation therapy
Oral medications
Corticosteroids

Surgery

Surgery is the most common way of treating mast cell tumors in dogs. The procedure involves putting the dog under anesthesia and surgically removing the tumor. Usually, your veterinarian will remove a 2–3cm circle of the surrounding normal tissue to reduce the chances of any cancer being left behind and minimize the risk of it spreading to other parts of the body. This process is called getting clean margins.

Surgery is a viable option for easy-to-reach and low-grade tumors, but clean margins are very important. Failing to remove enough surrounding tissue leads to a 25–40% chance of the tumor reoccurring.1

Things to consider about surgery :

  • Anesthesia may pose a health risk to some dogs, particularly senior dogs, short-muzzled (brachycephalic) breeds like Pugs and Bulldogs, and those with underlying health conditions
  • 40–50% of mast cell tumors on dog’s skin occur on their legs, where it can be difficult to remove enough tissue to get clean margins2
  • If multiple tumors have occurred, repeated surgery can be challenging
  • Some tumors are located in areas where surgery may not be the best cosmetic option or could hinder the dog’s ability to do basic things like go to the bathroom, in which case the initial surgery may be followed with reconstructive surgery.

STELFONTA® (tigilanol tiglate injection)

STELFONTA removes mast cell tumors without surgery.   Your dog does not need to be put under anesthesia but may need to be sedated to allow the veterinarian easy access to the tumor.

Offering strong efficacy, 87% of mast cell tumors are destroyed with one or two injections.3,4 With no chemotherapy or radiation involved.

STELFONTA starts working within hours to destroy your dog’s tumor.  This creates a temporary wound once the tumor sloughs away.  Most sites are fully healed within 4–6 weeks of the initial injection.3,4

There are a number of things to consider before deciding whether STELFONTA may be a suitable treatment option for your dog, including size and location of the tumor.

Learn more

Chemotherapy

Chemotherapy is generally reserved for high-grade canine mast cell tumors, where the cancer has spread to other areas, or where there is a risk surgery did not remove the full tumor. It can be used to delay the tumor from spreading, control spreading if it has already occurred, or minimize the dog’s discomfort.5,6

This type of cancer treatment is often used in combination with steroids to shrink the size of a dog’s tumor and improve the success rate of surgery. Things to consider about chemotherapy:

  • Side effects may include reduced white blood cell counts (bone marrow suppression) and gastrointestinal upset
  • Can be costly
  • Not widely available

Radiation therapy

A treatment typically performed at a veterinary speciality hospital or clinic to reduce a mast cell tumor’s size and control or kill the existing cancer cells. This procedure is generally used alone or in combination with other therapies to treat the tumor.

Things to consider about radiation therapy:

  • Successful treatment often requires multiple treatments
  • Dogs usually need to be put under anesthesia each time to target only the tumor area
  • Anesthesia may pose a health risk to some dogs, particularly senior dogs, short-muzzled (brachycephalic) breeds like Pugs and Bulldogs, and those with underlying health conditions
  • Can be costly
  • Risk of long-term and short-term side effects
  • Availability is limited

Oral medications

There are cancer therapy medications dogs can take by mouth, for example toceranib phosphate (marketed as PALLADIA™) which has been shown to shrink 37.2% of tumors by at least 30% when used alone.9 A clinical study has shown that toceranib phosphate is most effective when combined with other treatments, and has been shown to shrink 76.4% of tumors when combined with predinisone and radiation therapy.8

Like all drugs, toceranib phosphate may cause side effects, even at the prescribed dose. Serious side effects can occur and may in some situations result in death. The most common side effects which may occur with toceranib phosphate include diarrhea, decreased/loss of appetite, lameness, weight loss and blood in the stool.9

Corticosteroids

Corticosteroids  are a low-cost option to control cancer and reduce inflammation when used in combination with other treatments. Corticosteroids are often used before surgery or STELFONTA treatment to shrink mast cell tumors. They are also used in combination with chemotherapy or radiation for mast cell tumors that cannot be surgically removed. Steroids tend to be less effective on their own and usually only effective for a short time.10

Side effects from short-term use of corticosteroids are typically mild (increased urination, thirst, appetite, and panting). Long term use or high doses can cause significant side effects, including:

  • Cushing’s disease
  • Diabetes
  • Increased risk of infection
  • Changes in behavior
  • Vomiting or diarrhea
  • Digestive tract ulceration
  • Lethargy

Corticosteroids react with a number of other drugs so it’s important to tell your veterinarian what other medication your dog is taking.

References

  1. Bergman P. Canine mast cell tumors: Margins. markers and prognostic factors. Kansas City, MO: Central Veterinary Conference;2010.
  2. Welle MM, Bley CR, Howard J, Rüfenacht S. Canine mast cell tumours: a review of the pathogenesis, clinical features, pathology and treatment. Vet Dermatol. 2008;19:321–339.
  3. US STELFONTA® (tigilanol tiglate injection) packaging insert. (2024)
  4. De Ridder TR, et al. J Vet Intern Med 2020 ;doi :10.1111/jvim.15806.
  5. Couto CG. Mast Cell Tumors: To cut or not to cut. Columbus. OH: Midwest Veterinary Conference:2018. https://www.michvma.org/resources/Documents/MVC/2018%20Proceedings/couto_04.pdf. Accessed May 22, 2019.
  6. Thamm DH, Turek MM. Vail DM. Outcome and prognostic factors following adjuvant pred./vinblast. chemotherapy for high-risk canine mast cell tumour: 61 cases. J Vet Med Sci 2006;68(6):581-7.
  7. Garrett L. Canine mast cell tumors: diagnosis, treatment, and prognosis. Vet Med· Res Reports. 2014(5):49-5
  8. Carlsten KS. London CA. Haney S, et al. Multicenter prospective trial of hypofractionated radiation treatment, toceranib, and pred. for measurable canine mast cell tumors. JVIM. 2012;26:135-141.
  9. PALLADIA (toceranib phosphate) [USA package insert].
  10. Mccaw DL, Miller MA, Ogilvie GK, et al. Response of Canine Mast Cell Tumors to Treatment with Oral Pred. JVJM. 1994;8(6):406-408.

FDA-CVM WARNING: SEVERE WOUND FORMATION IN HUMANS; EXTENSIVE WOUND FORMATION, MAST CELL DEGRANULATION, AND DEATH IN DOGS DUE TO MAST CELL DEGRANULATION

Human Safety

  • Accidental self-injection of STELFONTA® may cause severe wound formation. To decrease the risk of accidental self-injection, sedation of the dog may be necessary (see Dosage and Administration, Human Warnings and Adverse Reactions).

Dog Safety

  • Always administer a corticosteroid, an H1 receptor blocking agent (e.g. diphenhydramine), and an H2 receptor blocking agent (e.g. famotidine) when treating with STELFONTA to decrease the potential for severe systemic adverse reactions, including death, from mast cell degranulation (see Contraindications and Dosage and Administration).
  • Do not inject STELFONTA into subcutaneous mast cell tumors located above the elbow or hock (e.g. on the body, head, or neck). This may result in accumulation of necrotic debris in the subcutaneous space increasing the risk of systemic adverse reactions, including death, from mast cell degranulation (see Contraindications, Warnings and Adverse Events).
  • Treatment with STELFONTA has been associated with cellulitis and severe tissue sloughing extending away from the treated site resulting in extensive wounds that require additional treatment and prolonged recovery times (see Warnings, Precautions and Adverse Events).

IMPORTANT SAFETY INFORMATION
Formation of wounds, possibly extensive, is an intended and likely response to treatment with STELFONTA along with associated swelling, bruising and pain; these wounds are expected to heal. Appropriate pre- and post-treatment medications must be given, including a corticosteroid plus blocking agents for both H1 and H2 receptors, in order to decrease the potential for severe systemic adverse reactions, including death, from mast cell degranulation.

Full prescribing information