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Dog Mammary Cancer Life Expectancy

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Dog Mammary Cancer

If your dog is suffering from mammary cancer, you may be wondering what a dog mammary cancer life expectancy is expected to be. The answer is that there is really no definite answer considering that there are several factors to consider when it comes to this type of cancer. Factors may include the age of the dog, how advanced the cancer is and whether the owner has financial capabilities to get the tumor surgically removed in a timely manner (surgery for breast cancer in dogs can easily cost anywhere between $500 and $2,000.) Following is some information about mammary cancer in dogs and potential dog mammary cancer life expectancy.

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Dog mammary tumor picture

Mammary Cancer in Dogs

Mammary cancer in dogs is the most common type of cancer affecting intact (not spayed) female dogs. In male dogs, this type of cancer is almost non-existent, with less than one percent of the tumors affecting male dogs. Compared to humans, this cancer is three time more likely to occur compared to its incidence in people.

In female dogs, mammary cancer is triggered for the most part by hormones which is one reason why veterinarians recommend getting female dogs spayed. The incidence of an intact female dog getting this type of cancer is seven times higher compared to spayed females.

Data shows that female dogs spayed before their first heat cycle had the lowest risk for mammary cancer; however, the risks still remain quite low if the dog is spayed prior to reaching the age of 2 and a half years.

"The risk of mammary tumor development for dogs spayed before their first estrus is only 0.05%. In dogs spayed after the first estrus, the risk is 8% and 26% if spayed after the second estrus."~The Cancer Center at Cares

A Serious Cancer

breast cancer on dog

Picture of breast cancer in dog

Mammary cancer in dogs is a serious and aggressive cancer. This cancer tends to go by a 50/50/50 rule. Out of 100 dogs with a bump in the mammary gland, 50 percent are a malignancy, and out of that 50 percent of malignant cancers, 50 will have spread to other sites by the time they are diagnosed.

The most common sites this type of cancer spreads to include the dog's nearby lymph nodes (axillary and inguinal) and lungs, but this cancer can sometimes also spread to the dog's brain and liver.

If the cancer is allowed to progress, the tumor grows larger, up to a point where it will start to weep, bleed and can become infected. The vet may instruct how to apply an Ace bandage around the dog's abdomen to protect the mass and apply pressure to help stop any bleeding.

When the lungs become involved, the dog then may start coughing and have trouble breathing. Affected dogs may then start to refuse food and they may become weak and lose weight.

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Treating Mammary Cancer 

The vet may prescribe prednisone to reduce any inflammation and antibiotics to fight any infections. Pain meds may be prescribed for pain and may consist of non-steroidal anti-inflammatory drugs (Previcox has been reported to have anti-tumoral effects) or for severe pain, narcotics may be prescribed. A word of caution though: steroids and anti-inflammatory drugs should not be used together and require a wash-out period, consult with your vet to prevent problems.

The most effective treatment for mammary cancer in dogs is surgery (mastectomy). The surgery should be carried out as soon as possible after having a fine needle aspiration performed to determine exactly what type of tumor is present. The surgery may be a minor procedure if there's a single small mass or it may be quite invasive if it requires removal of the entire mammary chain on the affected side along with the regional lymph nodes.

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Following up with chemo may be helpful, but data has not determined yet if it is beneficial. Consulting with a veterinary oncologist may be insightful to learn more about this option.

Dog Mammary Cancer Life Expectancy

As mentioned, life expectancy for dogs with mammary cancer is based on several factors. Because of the many factors, life expectancy can vary widely from dogs living just a few months in the most advanced cases, to dogs normally living out the rest of their lives in the case of small cancers that haven't had the opportunity to spread.

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Interestingly, survival times seem not to be influenced by the location of the tumor or their numbers. Following are several factors and the role they play in the life expectancy in a dog with mammary cancer.

Stage of Cancer

One important factor is how advanced the cancer is. Stages of cancer are different types of scores that are given to cancers based on how much they have grown and their sizes and these can provide an insight into life expectancy. For instance, dogs with stage 1 mammary tumors have the best prognosis as these cancers are curative and dogs therefore get to survive longer.

Also, the type of cancer is a factor. The most common type of mammary cancer in dogs are carcinomas (Allen et al. 1986, Lana et al. 2007). Dogs with inflammatory mammary carcinoma (IMC), a rare cancer considering that only 7.6% of mammary tumors in dogs are classified as IMC, instead have a poor survival rate (an average of 25 days!) considering that sadly no effective treatment has yet been discovered.

Size of Cancer

Size also matters. According to a study, dogs who had mammary tumors that were smaller than 3 cm in diameter (about 1.18 inches), had a better life expectancy than dogs who had tumors larger than 5 cm (almost 2 inches) which were more likely to die in the first two years following surgery.

Another factor is how the cancer affects the skin. If there is ulceration over the skin, this can be an indicator of shorter survival times than dogs who had tumors without ulceration. Rapid growth of the tumor also had a worse prognosis.

Spread of Cancer

Whether the cancer has spread is a very important prognostic factor. Dogs with mammary cancer that has not yet spread were found to be three time more likely to survive one year after diagnosis. Decreased survival is expected in mammary cancers that have spread to the dog's regional lymph nodes and distant sites such as the lungs.

A chest x-rays can show whether a dog's mammary cancer has spread to the dog's lungs. In a dog with the tumor that has spread to the lungs, the life expectancy may be poor, ranging anywhere between three and six months, explains veterinarian Dr. Gabby.

Duration of Presence

Noticing a mammary gland tumor as early as possible is important and reporting its presence to the vet promptly can make a difference. It has been found that dogs who had a mammary tumor for more than 6 months were more likely to have it spread than dogs with tumors that were surgically removed shortly after diagnosis.

Age of Dog

Age is quite important when it comes to determining life expectancy. In older dogs, studies have found the prognosis tends to be worse than younger dogs.

As seen, there are several factors to consider that can have an impact on a dog's mammary cancer life expectancy. According to a study, the the mean survival time of dogs with non-IMC malignant mammary tumors is 14.2 mo with surgical treatment alone.

References:

  • DVM360: Prognosis, treatment of canine mammary tumors
  • Good Old Dog: Expert Advice for Keeping Your Aging Dog Happy, Healthy and Comfortable, By Cummings School of Veterinary Medicine
  • Chang SC, Chang CC, Chang TJ, Wong ML. Prognostic factors associated with survival two years after surgery in dogs with malignant mammary tumors: 79 cases (1998–2002) J Am Vet Med Assoc. 2005;227:1625–1629.
  • Perez-Alenza MD, Tabañera H, Pena L. Inflammatory mammary carcinoma in dogs: 33 cases (1995–1999) J Am Vet Med Assoc. 2001;219:1110–1114
  • Sorenmo, K. U., Shofer, F. S., and Goldschmidt, M. H. Effect of spaying and timing of spaying on survival of dogs with mammary carcinoma. J.Vet Intern Med 14, 266-270. 2000.
  • Philibert JC, Snyder PW, Glickman N, Glickman LT, Knapp DW, Waters DJ: Influence of host factors on survival in dogs with malignant mammary gland tumors. J Vet Intern Med 17:102-106, 2003

Photo Credits:

  • Mammary tumor in a dog, Joel Mills - Own work Mammary tumor in a fourteen year old Labrador Retriever. The tumor is about eight centimeters in length. It was confirmed to be a carcinoma on histopathology. CC BY-SA 3.0
  • Female dog with a 9-month-old mammary tumor, by L. MahinGNU Free Documentation License, Version 1.2

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