Both trends suggest that widespread mammography screening, along with improvements in imaging technology and increased biopsy rates, among other factors, are catching breast cancer earlier, before it starts to spread and becomes more life-threatening, according to a new study by Christopher Li, M.D., Ph.D., and colleagues at Fred Hutchinson Cancer Research Center.
"The results of this study suggest that our public-health efforts to increase the use of breast-cancer screening appear to have altered the types of breast cancer that are being diagnosed most frequently in the United States, as we have found that the number of invasive cases being diagnosed has stabilised, while more cases of in situ breast cancer are being diagnosed," said Li, an assistant member of Fred Hutchinson's Public Health Sciences Division.
Li and colleagues also found a sixfold increase in noncomedo DCIS, while incidence rates of a potentially more aggressive type, comedo DCIS, have declined during the last five years.
"This suggests a further downshifting of severity within in situ cancers themselves," Li said. The researchers also found that rates of a less common precancerous condition called lobular carcinoma in situ, or LCIS, has increased nearly fourfold in postmenopausal women since 1980.
"Some small studies do indicate that women with LCIS are equally likely to develop cancer in one or both breasts, so oftentimes it is considered a nonsurgical disease, because the only logical treatment would be a bilateral mastectomy, which would be unnecessary in the vast majority of cases," Li said.
"Given that rates of DCIS and LCIS continue to increase in the United States, clinically useful tools that improve our abilities to stratify these patients based on their risk of invasive cancer are needed," Li and colleagues wrote.
MEDICA.de; Source: Fred Hutchinson Cancer Research Center