A new study says most cancer screenings don't actually end up extending life. But experts still say you should have them. The reason for the recommendation to have regular screenings is to catch cancer early so doctors can take action as soon as possible and improve a patient's chance of surviving the disease. The latest review of clinical trials published in the journal JAMA Internal Medicine finds that of the six most common screenings for cancer, only colorectal cancer screening with sigmoidoscopy made a difference