Interval breast cancers may be more aggressive

New research shows that breast cancers discovered between regular mammogram screenings (interval cancers) are more aggressive than those detected during routine screening. Published in the May 3 issue of The Journal of the National Cancer Institute, the study assessed the medical records of more than 430,000 women over 50 years of age who were screened biennially between 1994 and 2002 as part of the Ontario Breast Screening Program. The researchers found 288 true interval cancers and compared them with 450 cancers detected at screening. They concluded that the interval cancers were biologically different from the overlooked cancers and were twice as likely to be estrogen-, progesterone-, and HER-2 receptor negative tumors — the so-called “triple-negative tumors” — which are much harder to treat.