Benign Fatty Tumors

My mother's dog, a Smooth Coat Collie, has massive benign fatty tumors all over his body. It's so bad, now, that his hips are affected, and I'm sure his internal organs are, too. Some are the size of a melon. I'm personally convinced it's his kibbles. Her veterinarian says there's nothing to be done about them, excpet surgery, of course, to the tune of thousands of dollars. He's had two surgeries, and they grew back, rapidly. I'm very worried. Is there ANYTHING that can be done? Can she change his diet? He has such a beautiful Spirit. I hate to see him suffer so much.