Cherry Tree Canker?

 I think my 25 year old cherry tree has canker and has done for sometime approx 5 years ago it started to ooze sap , I'm annoyed for not realising what it was earlier but up to 2 years ago it was plentiful in fruit, the last two years I had blamed the lack of fruit on the strong winds blowing all the cherries off. I see an article where they cut the canker out of a fruit tree but think mine may be too far gone, I don't really want to have to chop my tree down as otherwise seems pretty green but if left afraid disease will spread within my garden any advice would be greatly appreciated.