You both use the word "cancer" in very general terms. There are many forms of cancer, each of which develop and spread at different rates. To simplify it down to whether or not you seek treatment just ignores the many factors that come into play. He has said that he's had explorative and preventative treatment. He's also been the usual droll Morrissey about it all. The leap, in some quarters, that he staring down the barrel of a gun is... jumping it!
It's no secret that he had a very romanticised idea of dying, without taking fully into account the real pain involved. Untreated cancer is not a glamorous death, it's a very slow and very painful one.