Treatment options available and prognosis (NC State University – Veterinary Hospital)

Surgery

• Wide surgical resection is recommended for malignant mammary masses.
• Benign tumors require less aggressive surgical margins.
• Surgery is the only treatment required for benign tumors and some malignant tumors.
• Dogs with large tumors, high-grade tumors, tumors that have already spread, and certain histological types are at higher risk for regrowth and spread following surgery.
• Multiple tumors can be removed at the same time.
  • Each tumor should be submitted for biopsy because they can all be different. (NC State University – Veterinary Hospital)

Dogs spayed at the time, or within 2 years, of tumor removal lived longer than un-spayed dogs in one study.

Radiation Therapy

• Radiation therapy (RT) has not been investigated for the treatment of mammary tumors in dogs, despite playing a big role in the treatment of this disease in people.
• Possible uses include pre-operative irradiation of large tumors, post-operative irradiation of incompletely resected tumors, or palliative irradiation of inoperable tumors.
• Dogs with inflammatory mammary carcinoma may benefit from radiation therapy.

Chemotherapy

• The role of chemotherapy for dogs with malignant mammary tumors is not well-established. Chemotherapy is recommended for dogs with higher risk of metastasis or tumors that already metastasized.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

• NSAIDs play a role in treating many different types of carcinomas. Dogs with mammary carcinoma can benefit from receiving an NSAID. 

Prognosis

The prognosis for dogs with benign tumors is excellent.

• About half of the dogs with malignant tumors also have an excellent prognosis with surgery alone.
• The remaining 50% of dogs with malignant tumors are at risk for the spread of their tumor. This leads to illness and poor quality of life, with survival times usually less than one year.

Dogs with inflammatory mammary carcinoma and mammary sarcomas have a poor prognosis, on the order of weeks to months.  (NC State)

Surgery and Spaying: (ACVS)

Further consultation with your primary care veterinarian may result in a referral to an ACVS board-certified veterinary surgeon to fully explore your options.

• The type of surgery depends on the size, location, and number of mammary tumors and species of your pet.
  •  In general, surgery is more conservative for dogs with mammary tumors and involves removal of either the mass alone or the affected mammary gland.
  • However, in cats, more aggressive surgery is recommended with removal of one or preferably both sets of mammary glands.  Surgery to remove both sets of mammary glands from a cat is often done in two surgical procedures 2–3 weeks apart. The local lymph node should also be removed in cats, if possible, to assess for evidence of spread of the cancer.
• The role of spaying female dogs with mammary tumors is controversial. Most studies have shown no beneficial effect of spaying at the time of tumor removal in preventing the development of new mammary tumors or influencing the aggressiveness or metastatic potential of existing mammary tumors.
  • However, spaying at the time of mammary tumor resection may be recommended by your veterinary surgeon because recent studies have shown a beneficial effect in dogs with mammary tumors, and it can prevent unrelated diseases, such as pyometra (uterine infection). (ACVS)