another colonoscopy

Hi again, yet more questions. I was diagnosed by colonoscopy, MRI, bloodwork....ect. Have been on chemo 19 months. Have not had another colonoscopy since all this started. The doc kept saying I was not bleeding there was no need to mess adround in there and possibly start problems. Had my usual 2 week appointment and chemo on Tuesday. Asked a bunch of queations, got the same answers.... then he says," when is the last time we did a colonoscopy? How long has it been?" I tell him, he looks through the chart and says"lets do one and see what that tumor looks like"  To tell you the truth, I am shocked he has decided to do this, told me 2 weeks ago he didn't think it was a good idea,....why now? This was after a disc...