The problem with just bluntly 'cutting it out' though, is the quick fixes we'd like to institute may well eradicate most of the original cancer, but we won't get it all and it will inevitably spread because of it.
You are 100% correct that is what happens. If you go back to the 2nd conflict with Iraq and the removal of Saddam Hussain, it then created an unstable country and led to groups such as ISIS gaining footholds. Saddam was an obvious cancer but by removing him the cancer actually spread and very widespread.
The debate on the removal of him is another topic but IMO it was a personal vendetta by George Bush Jr on behalf of his father and brought many nations along with them and has created the situation to an extent we have today.