Mammogram is showing its benefits
DCIS is the earliest stage of breast cancer known as stage 0 breast cancer. Since 1980 the incidence of DCIS has markedly increased by about seven fold, while the more advanced invasive cancer has remained mostly unchanged. Both of this trends suggest that use of screening mammogram which has become more popular since 1980 had an impact on breast cancer. These findings are from a large study by Christopher Li, M.D., Ph.D., and colleagues at Fred Hutchinson Cancer Research Center, published in the April issue of Cancer Epidemiology, Biomarkers and Prevention. Read more about DCIS...
This study was based on data from 32,990 women diagnosed with DCIS and 5,462 women diagnosed with LCIS between 1980 and 2001. Cases were identified through nine population-based cancer registries that participate in the Surveillance, Epidemiology, and End Results, or SEER, Program, which is funded by the National Cancer Institute. The registries represented women from Connecticut, Hawaii, Iowa, New Mexico, Utah, and the metropolitan areas of Atlanta, Detroit, San Francisco-Oakland and Seattle-Puget Sound. The NCI funded the research.
"The results of this study suggest that our public-health efforts to increase the use of breast-cancer screening — mammography, primarily — 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 stabilized, while more cases of in situ breast cancer are being diagnosed," said Li, an assistant member of Fred Hutchinson's Public Health Sciences Division.
The study also found a sixfold increase in a less aggressive subtype of ductal carcinoma in situ, a condition called noncomedo DCIS, while incidence rates of a potentially more aggressive type, called 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. Read more about LCIS...
These findings, based on the most comprehensive assessment to date of age-specific incidence rates of in situ breast cancer, while encouraging, also pose a particular challenge to health-care professionals.
"There is good news in that it appears we are detecting breast cancer at an earlier stage. However, the increasing number of in situ cancers presents an important clinical challenge, since in some cases the treatments that should be given to women with these conditions, primarily LCIS, is unclear," Li said. "Another problem is that we are not very good at predicting which women with these precancerous lesions will develop invasive breast cancer and which will not," said Li, also a research assistant professor in the Department of Epidemiology at the University of Washington School of Public Health and Community Medicine.
"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. "However, if we could develop new tools to predict which women with LCIS are more likely to develop invasive cancer we could better counsel them on what might be appropriate treatment options," he 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.