How common is mammary cancer in unspayed or late spayed cats?

Cataria

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3-5 years back, I went through a very rough patch patch with the two kitties I had at the time, Ember and Sweetie. My family found Ember and Sweetie when they were little kittens and took them in. I was still in school and my family was into saving money and avoiding vet bills at the time, so they were not spayed. They were indoor cats, so they never had kittens, and their heats, although loud and annoying, didn't involve any spraying or bleeding, so at the time and not knowing any better, it seemed reasonable.

When they turned about seven years old, I moved out , took them with me, and got them spayed. During the spay surgery, they discovered that Sweetie had mammary cancer. A few months later, I found a tumor on Ember as well. After two years of vet visits and chemotherapy and mastectomies and still losing them, you can bet that I learned my lesson; pregnancy is not the only risk you have by not spaying!

However, since then, cancer and not spaying is something I have been incredibly paranoid about, and although I know not spaying Ember and Sweetie until they were 7 was a large contributor to them getting cancer, I am curious if late spays always up the risk up mammary cancer, or if it is only cats who have not been spayed but have never had kittens that have the major risk.

I worry especially because two of the cats I have now I didn't get until they were at least a year old, so I couldn't get them spayed young -- Nenya was probably about a year old when she was spayed, and Meko was maybe 3. Is mammary cancer a reasonable concern, or am I'm just worrying too much?
 

stephenq

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3-5 years back, I went through a very rough patch patch with the two kitties I had at the time, Ember and Sweetie. My family found Ember and Sweetie when they were little kittens and took them in. I was still in school and my family was into saving money and avoiding vet bills at the time, so they were not spayed. They were indoor cats, so they never had kittens, and their heats, although loud and annoying, didn't involve any spraying or bleeding, so at the time and not knowing any better, it seemed reasonable.

When they turned about seven years old, I moved out , took them with me, and got them spayed. During the spay surgery, they discovered that Sweetie had mammary cancer. A few months later, I found a tumor on Ember as well. After two years of vet visits and chemotherapy and mastectomies and still losing them, you can bet that I learned my lesson; pregnancy is not the only risk you have by not spaying!

However, since then, cancer and not spaying is something I have been incredibly paranoid about, and although I know not spaying Ember and Sweetie until they were 7 was a large contributor to them getting cancer, I am curious if late spays always up the risk up mammary cancer, or if it is only cats who have not been spayed but have never had kittens that have the major risk.

I worry especially because two of the cats I have now I didn't get until they were at least a year old, so I couldn't get them spayed young -- Nenya was probably about a year old when she was spayed, and Meko was maybe 3. Is mammary cancer a reasonable concern, or am I'm just worrying too much?
Sad but good info.  I don't know how common it is but the longer they go unspayed, the greater the risk.
 

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Those are excellent questions. I know that spaying prior to the first heat cycle is best when it comes to preventing mammary cancer.

The idea is that every heat cycle pushes the tissues of the mammary glands, ovaries and uterus to become more active and thus new cells are formed and die. Whenever you stress any tissue into this process, the risk for cancer is increased. Every time a cell divides to create a copy of itself in our body here's some very minimal risk that an error in the replication of the genetic material may cause the new cell to be cancerous. It's like playing Russian roulette and it happens all over our body every day. Most times "bad" cells just die off or are being killed by the body. Rare mutations may survive and become cancer. So, to reduce the odds of getting cancer, we want to reduce injury to cells and any process which "activates" tissues and gets their cells to replicate more often. Heat cycles are such processes.

I'm not sure if there's enough epidemiological evidence to provide you with an answer as to how much early spaying reduces the chance of mammary cancers. I have found this -
Moreover, says Andrea Looney, DVM, a lecturer in anesthesiology at the Cornell University Hospital for Animals, neutering at an early age is likely to spare a cat from several lethal health problems later on in its life. As Dr. Looney points out, spaying a female kitten when she is three to six months old—when her reproductive organs are nearing maturity but before her breast tissue develops—will virtually eliminate her risk formammary cancer  later in life. Also, since spaying entails the removal of a female’s uterus, Dr. Looney notes, the procedure rules out the possibility of pyometra, a potentially fatal collection of pus in that reproductive organ.
It's simply the logic of providing cancer less of a chance to develop by preventing certain tissues from being "awakened" by hormones into enhanced cell division.
 
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Cataria

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Thank you both. So it would be a reasonable assumption that a cat that wasn't spayed until 3 years old has more of a chance than one spayed at 6 months, but hopefully much less than a cat not spayed until 7?

I have been somewhat considering getting pet insurance on Meko (the one who was probably 3 when she was spayed), to try to avoid the tough decisions I had to make with Ember and Sweetie. After Sweetie was diagnosed, I highly considered getting insurance for Ember at the time but kept telling myself I was being paranoid. Turns out I wasn't, but it probably wouldn't have mattered anyway -- if I got it when I first considered it, I think she would have been diagnosed with cancer too soon afterwards for the insurance to be willing to cover it (at least for the insurance I was looking at).

I have four cats now, and I know there's no way I could afford insurance for all of them. Meko would have highest risk of mammary cancer of the four, and as the eldest, probably the highest risk for anything, but I can't decide if the cancer risk is truly that high or not. I mean, sure, she could always end up with some other problem that the insurance could cover, so it's not all about cancer, but then again, my other cats could have problems too, and they wouldn't be covered by insurance. Also, Meko is a tripod cat, and I assume the insurance would refuse to pay for any issues she might have when she's older that would be related to her missing leg since that would be a preexisting condition, which also makes it seems like a bit of a waste.

I'm overthinking it.
 

misterwhiskers

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I believe that like humans, the chance for cancer increases if there are no babies.

This is Tootise.

She died of mammary cancer at age 7, having been fixed at six months. But she was exposed to a lot of insecticides after our cellar was infested with fleas when she was about 5. So there really are other variables.
 
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