You do not have to have the symptoms of cancer to get the test for some cancers. There are screening tests that are done sometimes based on family history, sometimes based on age. For instance, there is a recommendation for screening colonoscopies on every over 50 to screen for colon cancer. There are recommendations for women as far as mammograms to screen for breast cancer or PAP smears to screen for cervical cancer. It is recommended that men get a PSA blood test for prostate cancer. Many of these recommendations are up for debate and for a few, the recommendations have changed in the past few years.