Hi I Have A 14 Yr Okd Staffordshire Bull Terrier

Hi i have a 14 yr okd staffordshire bull terrier and he has the most leathal farts ever could this be down to age he has bad back legs and has a lump on back of his back leg the vet said its cancer but wont give him anything as he aint in pain and most so because of his age she said u have to keep an eye on the lump to