My dog isn't interested in playing fetch and won't drop the toy.

My dog is very food driven and will play fetch when incentivised by a treat. However, when playing regular fetch, he'll be able to fetch the toy and bring it back to me - but won't drop it. He'd rather me chase him for the toy rather than him chasing the toy and bringing it back to me. I'd like to know if there are any training methods to help him have more fun with fetch. He's 4 yrs old.