A study presented December 11 at the San Antonio Breast Cancer Symposium maintains that the controversy over the benefits and harms of breast cancer screening is "artificial."
The authors published their research last month in an article in the journal Breast Cancer Management, and determined that once data found in four large studies on breast cancer screening was standardized to a common screening scenario, the differences between their results were significantly reduced.
"We wanted to understand why these estimates differ so much," Robert A. Smith, Ph.D., of the American Cancer Society, said according to AuntMinnie.com. "What we found was that the estimates are all based on different situations, with different age groups being screened, different screening and follow-up periods, and different in whether they refer to the number of women invited for screening or the number of women actually screened."
Smith and colleagues compared the Nordic Cochrane review, the U.K. Independent Breast Screening review, the U.S. Preventive Services Task Force (USPSTF) review, and the European Screening Network (EUROSCREEN) review. They converted all of those to the same scenario as used in the U.K. review, which, according to Smith, used a standard screening population conducted by an independent group of experts with no mammography screening background to help them avoid bias.
Once the results of the other three studies were standardized, the differences in their findings were minimized, the study's authors said. In the Nordic Cochrane review, the estimate of the number of women who must be screened to prevent one breast cancer death decreased from 2,000 to 257; the USPSTF estimate dropped from 1,339 for women aged 50 to 59 and 337 for women 60 to 69 to 193 for women 50 to 69. The EUROSCREEN estimate decreased from 111 to 64.
The "controversy over the effect of mammographic screening on breast cancer mortality is largely artificial," the study's authors said. "When like is compared with like, the estimates from all major reviews of the subject point to a substantial and significant reduction in breast cancer deaths with the offer of screening. There are genuine disagreements about overdiagnosis, but estimation methods that properly take into account the complicating factors of lead time and underlying incidence trends yield modest estimates of overdiagnosis."