Breast cancer screening uses an X-ray image called a mammogram to check the breasts for signs of cancer. It can find cancers that are too small to be felt. The earlier a breast cancer is found, the more effective treatment may be. Screening does not prevent breast cancer from developing, but it may find a breast cancer sooner, when the chance of successful treatment is higher. Mammography is currently the only screening method that has been proven to help prevent deaths from breast cancer.