Someone I know has an 8 year old dog with lymphoma. The first course of chemo put the dog in remission for 10 months. The dog has just dropped out of remission and the choice is a second course of chemo and the remission is likely to be similar or shorter or to go for a bone marrow transplant.
She has opted for the bone marrow transplant with a cure rate of 40%. There have been about 12 done where I live. The success rate depends on the type and spread of lymphoma when first discovered. The dog has to be put into remission and then bone marrow is harvested.
She has a blog which describes her journey with her dog which started in May 2007
Raven, Cypher & Spryte - An Agility Blog