At What Age to Spay/Neuter: An Evidence-Based Study

[jesirose]

Can someone explain this to me? The numbers are confusing me.

"Mammary neoplasia, or breast cancer, is a very common disorder of female dogs, with a reported incidence of 3.4%; this is most common tumor type in female dogs. Of female dogs with mammary tumors, 50.9% have malignant tumors. Risk factors for mammary neoplasia in female dogs include age, breed (Table 1), and sexually intact status. Multiple studies have documented that spaying bitches when young greatly decreases their risk of developing mammary neoplasia when aged. Compared with bitches left intact, those spayed before puberty have a 0.5% risk, those spayed after one estrous cycle have an 8.0% risk, and dogs spayed after two estrous cycles have a 26.0% risk of developing mammary neoplasia later in life. Overall, unspayed bitches have a seven times greater risk of developing mammary neoplasia than do those that are spayed."


Okay, so 3.4% of dogs get breast cancer. But 26% of dogs spayed after 2 cycles get it?

Is this saying that 26% of the dogs in the 3.4% were spayed after 2 cycles? So either way it's still only 3.4% of ALL dogs, it's just more common for those dogs to have been spayed after 2 cycles?

No, 3.4% is the reported percentage of dogs that get it. 26% is the RISK of them getting it if spayed after 2 heat cycles.

---> with a reported incidence of 3.4%

---> dogs spayed after two estrous cycles have a 26.0% risk

[jesirose]

I still don't understand that. What is the difference between the risk of them getting it and the incidence? If there is a 26% risk, shouldn't 26% of them get it?

No, just because there's a risk doesn't mean they'll get it. There's a statistical risk that I'll get in a car accident today, but it doesn't mean it'll actually happen.

The percentage of incidents is 3.4%, that's 3.4% that HAVE gotten it. But there's a 26% RISK that any female spayed after her second heat will get it. Just because the risk is there, doesn't mean it'll happen. It's a risk.

3.4% is the percentage of dogs that HAVE gotten it, and have been diagnosed with it.

It goes back to the car wreck analogy. For instance, say the department of transportation says that 40% of people driving a small car will get into a wreck this week. Just because there's a 40% risk of that happening, and I will be driving a car this week, doesn't mean I'll actually get into a wreck.

[jesirose]

No, but 40% of people will. Not always you, but 40%. So just because you don't, someone does.

How can there be a 26% risk unless 26% of them get it? What does 26% risk MEAN? And how does it relate to the 3.4% incidence? If only 3.4% of them get it, where are they getting 26% from?

So if I have 4 dogs and get them spayed after 2 cycles, statistically one of them will get it. If there is a 40% risk of getting in a car wreck that means if 10 of us go drive 4 will get in a wreck.

Maybe it's a two-part thing... I dunno. The article may have just written it in a weird way. I see it as, they did a study and 3.4% of the dogs got the tumor. And in their research, they came to the conclusion that 26% of dogs get it if spayed after their 2nd heat cycle.

I dunno, the piece of article doesn't give much to go on. It's all just numbers and statistics, and I've seen several different researches and websites quote different numbers on their conclusion of the percentage of dogs that will get reproductive or mammary cancers either due to early spay, or later spay, or no spay.

Numbers give me a headache, LOL. I'll leave it be, hopefully someone else can give you a more detailed answer, because I am stumped beyond what I talked about above.

[Ratboy]

I had Molly spayed as early as possible, but I waited on King until he was 3, as I have seen so many great young male pups with great personalities that after neutering were never the same, kind of dulled, I guess. King hasn't changed a bit, personality wise (This might be a negative in some people's opinions, King has a ton of personality! ), and the only physical changes we saw was he just wasn't quite as rock hard as he was before.

Of course, there was a negative to waiting, as King fathered 8 pups before he was a year old, due to the neighbor's dog running loose and jumping my fence. All those pups found good homes, so it worked out. I was going to take one of them if needed, as King and Molly both seemed to accept the pups jumping all over them when we walked over to visit pretty well.

My last dog, Gus, was never neutered, and he was put down at age 14.5. The vet said he thought it was prostate cancer from the looks of it. He said it was the worst he had ever seen and that Gus appeared to be pain free was a miracle and said if Gus was a human, he would have been screaming for morphine, or just to die.

[Dekka]

A neutered dog can still get prostrate cancer. The only cancer they can't get is testicular cancer.. as they no longer have testicles to get cancer in. And according to that article the dogs chances of prostratic cancer rise with altering.

IMO diet/environment has more to do with cancer that parts (except the parts you lop off can't get it)

[xpaeanx]

When determing if I should neuter Midget or not, I read a little more into it. I also found this other article that I like (as it cites sources which is something I always look for when reading for educational purposes).

http://www.naiaonline.org/pdfs/LongT...uterInDogs.pdf

[Amanda885]

Interesting....good info to know for sure. Thanks for posting it up! *thumbs up!*