Hi,

This question is aimed not just at the vets (maybe should be posted to Anything Goes?) -- but also to any others who have an opinion/anecdote/past research.  I've done a bit of research on my own regarding when to get the new baby spayed, but I know the level of research I did on Milo trying to understand his osteosarcoma was far deeper and more passion driven than anything I could do now.  Assuming others also did the same deep dive on their babies, I'd love to hear what you have learned and experienced.

Darcy-girl is 5.5 months old now.  We're working hard on cultivating all her wonderful potential!  It was only 3 weeks between losing 10-year-old, super-chill Milo and getting baby Darcy, with all of her crazy puppy energy.  No regrets!  She was just the medicine we needed!  More importantly, we want to keep her around and cancer-free and disease free as long as possible.  Hence the question on when to spay.

We will have her spayed, but the question is at what age.  I'm definitely not going through life with a female and worrying about accidental pregnancies!  There are numerous papers about different cancer related to neutered/intact dogs, but I haven't found as much about correlations with specific age of neutering. 

Osteosarcoma risk increases for males, big dogs, fast growth, and early neutering.  I also read for the first time that early-neutering results in the growth plates NOT closing as soon, so long bones in dogs may grow taller.  Milo was neutered by the breeder before 8 weeks.  His parents were ~60 pounds.  He grew to ~75 pounds, with very long legs (could rest chin on the dinner table.)  And we know his osteosarcoma story.... sigh....  He fit the study.

For females, it's not clear if the osteosarcoma risk varies with neutering in the same way.  There is an increased risk of mammary tumors if allowed one cycle, and significantly increased risk if multiple cycles.  My first thought was spay at 6 months -- no cycles!  But the risk of hemangiosarcoma increases 5-fold with spaying (age dependency?  1 year?)  Most of the other risks/dependencies are not show stoppers, although likelihood of urinary leakage with age goes up with earlier spaying. (maybe hip displasia, maybe cruciate ligament injuries, etc)

So.... if I had another boy, I would hold off on neutering until at least 1 year, possibly 2 if I could manage the behavior.  But it's not such a clear answer for my girl.  I believe the mammary tumor risk is more prevalent (spay early), but hemangiosarcoma in heart tissue is hard to detect and not really treatable (don't spay early).

Any insights or experiences would be appreciated.  I realize most cancer is a mystery and mostly out of my control, and I realize no matter what decision I make, I'm making the best decision I can for her, which is all I can do -- just like I did with Milo.  But the more info to help with the decision is always good.  Might as well try to help any little odds I can.

Peace,

Jenifer, Milo, and Baby Darcy