Do you mean Tom Watson's caddy that died a couple of years ago. It was not cancer but another rare disease.

Angelo Argea died in 2005 (Jack Nickluas Caddie) tall guy with white afro (cancer)

Bruce Edwards died in 2004 (Tom Watson caddie) Watsons main tour caddie of (Lou Gherig disease)

Was it Caddy for Life: The Bruce Edwards Story?

If so, it's here.

I didn't think much of Feinstein's A Good Walk Spoiled, but this has a rather more significant subject.

or are you thinking of Jeff 'Squeaky' Medlin?

Nicky Price's caddy who also carried John D's bag at crooked stick when he won the PGA as an alternate?

Second the recommendation of Four Iron, which I thought was insightful and funny. However, I went on to read Donegan's Quiet Please and thought his style had become a bit formulaic and rather annoying.

My favourite "fun" (as opposed to instructional) golf book is probably still My Baby Got The Yips, though.