I signed up just to reply here. Today I lost my 12 year old German Shepherd to hemangiosarcoma.
His name was Sam and he was huge and classically featured. A real gentle giant. Never stopped recieving comments from other dog walkers and even German Shepherd breeders at how handsome and proud he was and a credit to his breed. He was a rescue dog from a pound and I've never come across any other dog with such a deep personality. As strange as it sounds he had an awesome sense of humour too. Everyone loved him, even those people who don't take to dogs. I'm going to miss him terribly. He truely was my best mate.

I wanted to post my experiences on hemangiosarcoma. He was diagnosed in December 2008 after he became very tired and just not himself at all. After 3 vets visits I got him to a specialist and they performed an ultrasound on him, to find he was bleeding internally whilst the scan was taking place. Rushed into surgery an hour later for a splenectomy. It's a costly operation (£2,900 here in the UK) but for me it was a no brainer and worth every penny, I'd have paid twice that. The prognosis however was bleak. It's an aggressive cancer and he was predicted to survive somewhere between 2-4 months.
Chemotherapy for us was not an option. After much research we learnt it could not cure him and may extend his life for a month (at best). We took the decision not to put him through that. Chemotherapy would be intense and make him feel ill during treatment and for a few days after .... at 5 lots of treatment to retard the onset of cancer that would mean he may last an extra month, but around 15 of those days he'd be either undergoing treatment or feeling rough.
We switched his diet to a high protein diet so as to feed the patient and not the cancer. His meals consisted of fresh boiled chicken breast and boiled brown rice for every meal. (gravy can help make it more interesting for your dog if you like) Carbohydrates will feed the cancer as well as the dog. Proteins tend to feed the dog more than the cancer. We tried to pile weight onto him because cancer can strip weight away from patients and the longer you can keep it on the better.
He suffered from a constant fever throughout so keeping him cool and a constant supply of fresh water. He was happy enough for the most part and still playful. He did slow down little by little and we reduced his exercise regime accordingly.
We had to give him tablets from time to time and found smearing them in pate and making it a game helped make it the job fun for him. He was a picky eater at the best of times so tablets were a problem until we came up with this solution. It went from being a chore he hated to becoming a game he looked forward to.
Sadly, today, some 10 months and 2 weeks after his diagnosis Sam died. We're so grateful for the time we had left with him and after a prognosis of 2-4 months we feel we helped Sam as best we could. He was on a walk and suddenly went very lethargic, his gums became very pale and eyes glazed over. It was clear he was ill. We got him to the emergency vet straight away, by which time it was clear he wasn't going to recover.
For me and my family it's a terribly sad day. We've all lost a GIANT of a personality in our lives. Everyone feels their dog is special and they'd be right, but even by those standards Sam was something very special.
For anyone else reading this other than our experiences above which may help those in a similar situation I have the following advice.
1. Good vets are great. Find a good one and stick with them, but remember this; vets knows dogs but only YOU know YOUR dog. A vet can tell you test results etc etc but it's up to you to guage your dog's well being. Be honest with yourself and whatever you do don't keep a poorly dog alive out of selfishness.
2. Be prepared. Know you vets phone number and stick it in your cell phone (also the emergency vets number for out of hours calls). Know the location of the vets surgery too in case your pet becomes ill suddenly. It can save time.
3. Finally, appreciate your dog. Try to enjoy your times with your dog. Spoil them a little too. Dwelling too much on the cancer can ruin things ... and dogs will pick up on your bleak outlook. Your dog's spirits are important to their well being.
If you're in the same situation you have my sympathy and I wish you the best of luck .... now go and play with your dog. Seriously, go and play with them.