Questions about early detection

An analysis of breast cancer data has called into question prevailing beliefs about the value of early detection. The study, published June 8 in The New England Journal of Medicine, revealed that many small breast cancers have an excellent prognosis, not because they are caught early but because they are inherently slow-growing. Because these cancers often do not grow large enough to become significant within a patient’s lifetime, early detection could lead to overdiagnosis, said the researchers at Yale Cancer Center. In contrast, they noted, large tumors that cause most breast cancer deaths can become intrusive before detection by screening mammography. “Our analysis explains both how mammography causes overdiagnosis and why it is not more effective in improving outcomes for our patients,” said Donald R. Lannin, M.D., professor of surgery (oncology) and lead author of the paper. “More importantly, it questions some of our fundamental beliefs about the value of early detection.”