Can doctors allways see if u own cancer through the blood?

lets influence ur not fealing well and u own a blood test when u run to the doctor. will they allways be able to see if u hold cancer anywhere through the blood?Can doctors allways see if u own cancer through the blood?
no way! sometimes it take an x-ray or cell counts though it can be done by blood/urine liver check etc-
no. There is one test, a CA125, that can pick up giant levels of one enzyme specifically sometimes an indicator of prostate cancer, but otherwise blood tests are not an indicator of cancer