⏰🥱👉 TL;DR (for HSA parents who need perspective — not panic)

A new study by a globally recognized leader in veterinary education and research — published in July 2025 — found the median survival time in dogs with hemangiosarcoma is heavily influenced by how many dogs are euthanized soon after diagnosis. When you look more closely, survival rates vary widely based on tumor location, diagnostic clarity, and treatment decisions. In other words: the prognosis most HSA dog parents hear may not tell the full story.

When Cattie was diagnosed, I remember hearing words like “days,” “weeks,” and “very little time.” The statistics were terrifying — and at first glance, this new study from the Royal Veterinary College (RVC) in London seems to confirm that fear, reporting a median survival time (MST) of just 9 days for dogs diagnosed with HSA.

But when I read more closely, I realized that number isn’t as straightforward as it appears.

In fact, the report shows that this statistic is shaped, not just by the biology of hemangiosarcoma, but by how quickly dogs are euthanized following diagnosis. 

That distinction matters — a lot. It reads:

“…a common prevailing view of extremely poor prognosis for haemangiosarcoma could be promoting frequent euthanasia at presentation and therefore leading to a self-fulfilling prophecy and low survival times.”

Wow. 😮

What the Study Examined

The researchers analyzed 788 dogs diagnosed with HSA through general (“first-opinion”) veterinary practices.

When they calculated survival times, they included dogs who were:

• Euthanized on the same day as (or within a few days of) diagnosis

• Or euthanized before any treatment was attempted

When those cases are factored in, the median survival is 9 days, with only 12% of dogs surviving beyond one year.

But that is not the same as saying: “HSA kills most dogs in 9 days.” It’d be more accurate to say: “While most dogs with HSA eventually succumb, many are euthanized very shortly after diagnosis, and that dramatically impacts the reported survival time.”

Those are two very different things. And for families trying to decide what to do next, that difference is critical.

The Prognosis Changes When You Look Deeper

Once you separate out tumor location, evidence of metastasis (or lack of), and level of intervention, a much more nuanced picture appears: Dogs that had histopathologic confirmation (meaning that, after undergoing surgery, the dog’s tissue was examined under a microscope) lived significantly longer than those who did not, with an average median of 105 days. Also, 28% survived a year from the date of diagnosis, suggesting that a number of dogs, especially those with early-stage cancer, can benefit greatly from surgery.

In other words: There is no single “HSA prognosis.” There are many.

And some dogs absolutely live far beyond what the numbers suggest. In analyzing outliers among all dogs studied, researchers found the survival range extended up to 5 years.

Why Early Euthanasia Skews the Data

I want to be very clear and compassionate here. Many families choose early euthanasia out of shock, fear of their dog suffering, a senior dog’s age, financial limitations, simply being told there are “few (or no) options,” & the list goes on. There is no judgment in that — and in some cases, it is the most benevolent decision. It destroys me as I recall this, but Craig and I discussed it that day in the ER waiting room when the surgeon said she was “pretty confident” the culprit was HSA; the grim picture painted sounded utterly irredeemable and potentially cruel to Cattie, so the thought was, “Should we spare her?”

With that said, purely from a data perspective, each of those early euthanasias makes HSA appear even more insidious than it biologically has to be at the time of diagnosis.

That means when dog parents Google “HSA survival rate,” they’re often seeing a picture that has already been partially swayed by pressure-driven decisions — not just disease progression. That can steal hope before there is even time to fully understand the situation. Just as it almost stole ours.

This is not to say that early euthanasia should be ruled out, either. There are so many considerations, not the least of which is a dog’s age, or as difficult a decision: your ability to afford it. I just feel this data reinforces that putting a dog to sleep shouldn’t be the automatic default recommendation in all situations.

What This Has Changed for Me

The truth is: not much. It confirms what I suspected after my month-long research marathon — and we already know that Cat beat her “best case scenario prognosis” by months. But if I’d seen research like this from the very start, it would have shifted my mindset from:

“How long does Cat have to live?” to “Which group does she fall into — and what can we still influence?”

Rather than crying myself to sleep back then — thinking only about the 3-month death sentence that was handed down — I could have been focusing on the variables that mattered, with at least a little hope that there were still happy days, however numbered, on our horizon.

None of this erases the seriousness of hemangiosarcoma; it’d just be nice to have known.

The Takeaway

The fact is that hemangiosarcoma is an aggressive, unforgiving, heartbreaking cancer with no known cure. I know Cat will not survive it — but that doesn’t mean she can’t live a full life in the meantime. …Because the other fact is that the widely quoted survival statistics are not just a reflection of disease — they are also a manifestation of urgency, fear, panic, unfamiliarity, and the scantness of easily accessed, digestible information on a complex cancer with evolving nuance.

This study doesn’t just give us numbers. It gives us permission to slow down, ask the right questions, and confidently advocate for our dogs.

When this all began, I never in my wildest dreams thought we’d celebrate Cat’s 8th birthday — 5+ months after diagnosis — let alone a “no signs of metastasis” report card 3 months following that. It’s therefore my hope that this study can give those of you who are now in my old shoes the faith I didn’t have. ❤️

If you’d like to read more, here is a link to the paper, itself.