Screening is looking for cancer before a person has any symptoms. This can help find cancer at an early stage. When abnormal tissue or cancer is found early, it may be easier to treat. By the time symptoms appear, cancer may have begun to spread.
The goal of screening exams for early breast cancer detection is to find cancers before they start to cause symptoms. Screening refers to tests and examinations used to detect a disease, such as cancer, in people who do not have any symptoms. Early detection means applying a strategy that results in an earlier diagnosis of breast cancer than otherwise might have occurred.
Breast cancers that are detected (found) because they are causing symptoms tend to be relatively larger and are more likely to have spread beyond the breast. In contrast, breast cancers found during screening exams are more likely to be small and still confined to the breast.
The size of a breast cancer and how far it has spread are the most important factors in predicting the prognosis (the outlook for chances of survival) of a woman with this disease. Finding a breast cancer as early as possible greatly improves the likelihood that treatment will be successful. There is no question that early detection tests for breast cancer save many thousands of lives each year, and that many more lives could be saved if even more women and their health care providers took advantage of these tests.