How Long Can a Dog Live With Mammary Cancer

How long can a dog live with mammary cancer?  I am sure most veterinarians wish there were a clear-cut answer to this. Unfortunately, the life expectancy of a dog with mammary cancer really depends on a number of things.

I want to help you narrow down an actual number because, to me, that’s a lot more meaningful than leaving the question up in the air.  I want to give you enough information in this post to help you determine life expectancy in a dog with mammary cancer, as it relates to your situation.

According to the Veterinary Cancer Group, mammary tumors are reported to occur in approximately 2 out of 1000 female dogs.

The Big Question:  How Long Can a Dog Live With Mammary Cancer?

Canine mammary cancer can present as either benign or malignant. In fact, there’s a 50/50 chance of either diagnosis.  Dogs spayed before six months of age stand the best chance against acquiring mammary cancer in the first place.

I was able to find an abstract published in the Canadian Journal of Veterinary Medicine where a study was conducted on the tumors of 63 dogs. The tumors were surgically removed and measured for size. Diagnostic tests were done to determine if cancer had spread into the lymph nodes, and the tumors were graded and staged.

A complete explanation of the methods used can be found at The Canadian Journal of Veterinary Medicine, along with the citations for publication.

Sign up for a FREE 5 Day Course on Canine Cancer and Get Exclusive Access to A Support Group.  Access is ONLY available to those who sign up.  Keep reading…the sign up form is at the bottom of this post.


At the end of the study, the results showed that:

  1. 98% of dogs with mammary cancer in Stage 1 were still be alive after two years post-surgery.
  2. 75.8% of dogs with mammary cancer in Stage 3 lived one year post surgery. That number droped to 66.4% post-surgery after 2 years.
  3. 13.6% of dogs who began treatment at Stage 4, were still alive one year after surgery.

To simplify things, the earlier the tumors are found and treated, and the younger and healthier your dog, the better the outcome. Unfortunately, that’s about as precise as it gets.

Figuring it Out: A Canine Case-by-Case Study

You can’t tell by touching or palpating the lumps whether they are cancerous or not. The only way is to examine the tissue, which the veterinarian will do through a biopsy. In a biopsy, a small amount of tissue is removed and examined.  In the best case scenario, all of the lumps are benign.  However, you could be faced with other scenarios including:

  1. Some of the lumps are benign, but some are also malignant, meaning the cancer may have spread to the lungs and lymph nodes.

  2. The lumps are all malignant and have likely spread to other parts of the body.

  3. All the lumps are benign.

The Most Important Thing is Not to Delay an Appointment with The Veterinarian

By using fine-needle aspiration, the veterinarian is able to take a small tissue sample for further evaluation.  If there is more than one lump, all lumps must be tested because it is very possible for some to be benign (non-moving) and some to be malignant (moveable and likely to spread within the body). They are not all necessarily the same. In fact, there are different sub-types of malignant mammary gland cancer that will determine how aggressive the cancer actually is.

What Are The Signs and Symptoms of Mammary Cancer in Dogs?

In addition to seeing or feeling lumps in and around the breast tissue, you may also notice:

  • an unusual secretion draining from the nipple(s).
  • ulceration (in the case of large tumors)
  • inflammation
  • secondary infection which will leave your dog feeling under-the-weather

Again, the key is to be aware of what’s happening in your dog’s body and having any unusual lumps and bumps examined by a veterinarian.

Don’t forget to sign up for your free 5 day course below. By signing up, you’ll have exclusive rights to a members-only online support group for canine cancer.


Risk Factors for Mammary Gland Cancer in Dogs

Unspayed females are more likely to develop mammary cancer than any other dog. Hormones present in an unspayed female fuel the proliferation of tumors the way oxygen fuels a fire. However, if the tumors progress to malignancy, those same hormones are not needed any more.  At the point of malignancy, hormones are not needed to keep that fire burning.

The risk of a dog developing a mammary tumor is 0.5% if spayed before their first heat (approximately 6 months of age), 8% after their first heat, and 26% after their second heat.

In addition, mammary gland tumors are:

  • usually slow-growing
  • inflamed
  • moveable (implying a benign tumor)
  • affixed to skin or body wall

Treatment is Not a Cure, But No Treatment is Deadly

Most mammary tumors are removed surgically, taking a wide margin to determine whether or not the cancer has spread. Chemotherapy is not recommended in dogs with mammary gland tumors. The best course of action post-surgery is to maintain regular check-ups so that the veterinarian can intervene if any tumors come back.

Female dogs who present with mammary gland tumors either have a genetic predisposition to them, or were not spayed early enough. Other factors could include  obesity and immune function.

Quality of Life for Dogs Living with Mammary Gland Cancer

If you get the worst-case scenario news, ask your doctor how surgery will affect your dog. You may have to decide if the post-surgery quality-of-life is worth the procedure. Some questions to ask the veterinarian might include:

  • Is my dog strong enough to undergo anesthesia?
  • What will my dog’s quality of life be after surgery?
  • What is a realistic life expectancy with the surgery?
  • What is a realistic life expectancy without the surgery?
  • Is my dog in pain?
  • How can I keep my dog as healthy as possible through this process?

Living With the Prognosis

I wish I could have given you a definitive answer to your question on how long a dog can live with mammary cancer. As you can see, the answer is a moving target that is dependent on a lot of different things. You should know that new treatments are being studied all the time and researchers are getting closer to finding longer-term solutions for dogs with cancer. I realize that doesn’t help you much right now.

My best advice is to try and stay positive and work with your veterinarian to find the best possible treatment plan for your dog. Your beautiful dog is going to need a lot of care and love through this, and nobody is better equipped for that job than you are.

Thank you for taking the time to read this post. I want you to know who I am and what I’m all about. Everyone loves old-timey photos (right?) and I’ve plastered them all over My Story, so why not have a look?

I want to wish you the best of luck as you go through this process. Please share your story with others so that everyone can benefit. Let us know what works and what doesn’t. What was your experience with the veterinarian and what challenges did you face?


This course is only open to those who have read this post. Once subscribed, you will receive 5 emails from Monday to Friday. There will be a break in between, and a couple of weeks later I will continue to send updates on the best posts.

Each email will have a link to your course topic of the day.  Take a look at what you’ll get…for free!

  •  lists of clinical trials
  • a veterinarian medical glossary of terms
  • support group locations
  • and exclusive access to my Canine Cancer Support Forum group.

To register, please complete the sign-up form below and check your email for confirmation.  Your first course will be delivered on the first Monday following signup.