MRI and CT scans are helpfull tools to check on cancers ,also there is blood tests which is called tumor markers like PSA ,AFP,CA19-9,CA 125,CA15.3 checking on prostat,liver,colon/pancerase,ovaries and breast cancers respectivly. but all depends on which stage the cancer is ,the earlier the difficult to detect and vica versa the later the easier but then its too late ,mostly.
nabil