I had a dog with Lymphoma. I did catch it early but he passed in about 6 months, I did paliative treatment only. That is a fast moving cancer so, I would imagine, if you are now 8 months out, hopefully that us not the case.
Ghilly is correct, however, there may be some underlying infection, parasites or possibly Leukemia. I assume your Vet has done thorough blood work.
Are there any other swollen nodes under the legs in the arm pit area? Any swollen in the groin or back legs?
Any indication of possible dental issues going on?
Hope you can find an answer and please keep us updated.
Lymphadenopathy (swollen glands) can be caused by a number of different things. The most common cause is an infection somewhere in the body.
Have they tested your dog for allergies? Allergens can cause the lymph nodes to swell as well, and if there are allergens in her environment it might be the reason you have only been able to achieve a 75% reduction in swelling. The glands go down because of the antibiotic treatment, but the allergen(s) remain(s) in her environment, therefore the lymph nodes are constantly attempting to ward something off.
Allergies are one of the most difficult things to diagnose, and nothing is more challenging to diagnose than food allergies, but an allergy test will probably be a heck of a lot cheaper for you than a lot of other diagnostics and it will probably be the least unpleasant for your dog. If nothing turns out after the allergy test, THEN move on to the pricier and more involved tests.
Ghilly