Labrador retreiver cancer illness

Hi,

Our dog, a 13 year old labrador retreiver, has been diagnosed with cancer about year ago, and back then doctors said he didn't have more than a few months. Well, he has survived for almost a year with the cancer, but have been through ups and downs. He has been eating regular diet of chicken breast, and rice for almost a year.

However, he still can't digest the food well, and it has progressed worse now. He throws up several times a day, and has lost a about 10 - 20 lbs during the past few months. I really don't want to suffer if he is in pain, but I really want have to make the decision and put him to sleep because he's a family member.

Does anyone know if dogs go through a lot pain when they have cancer? Can anything be done to make him digest his food without throwing up the food? What ever he has been eating recently, he has vommited. He is on reglan(sp?), but still throws up on reglan as well.

thank you for you help.

John