Data from randomized trials of breast cancer screening and more recent evaluations of screening in community settings have shown that early detection of breast cancer is an important factor in reducing morbidity and mortality from breast cancer. Two new studies published in the journal Cancer provide additional evidence about the importance of early breast cancer detection.

One study, which evaluated a community screening program for women ages 50-69, showed that women who underwent screening had improved prognosis, improvements not evident in women who did not participate in screening. The second study, which reports data from long-term follow-up of a randomized trial initiated in 1970s, shows that twenty years after diagnosis, earlier detection is the most important prognostic factor in long-term outcomes.

Since the first trial of breast cancer screening more than 40 years ago, the accumulated evidence provides strong support for the conclusion that early detection saves lives. However, concerns about false positives and the detection and treatment of potentially benign lesions have made some question the social and medical value of breast cancer screening - particularly, in women in their 40s. Currently, consensus groups have concluded based on meta-analyses and clinical trials that breast cancer screening with regular screening mammography, and clinical breast exams reduce breast cancer mortality.

These two studies from Cancer demonstrate the benefits of data gleaned from population-based screening trials and service screening studies, and provide striking new evidence of the long-term prognostic value of detecting early breast cancer.

Dr. Jane Warwick and her colleagues evaluated data from the Swedish Two County Trial. They found that the tumor size and grade and lymph node status at diagnosis affect survival even 20 years later. The authors conclude that, "Firstly the pathological features of the tumor at diagnosis may have implications for long-term follow-up; secondly, the long-term effects of the prognostic factors may explain the fact that the impact of mass screening programs on breast cancer mortality rates is still apparent many years later."

Dr. Miranda F. Ernst and her colleagues evaluated the impact of a community-based biannual screening program introduced in 1992 for women 50 to 69 years old in the southern Netherlands. Comparing the period 1985-91 and 1992-1999, the authors found a significant increase in the diagnosis of stage I disease and significantly improved survival after the introduction of the screening program. However, at this early stage in the program, the data showed that 60 percent of the cases of breast cancer were detected between screenings or in those who did not participate in the program, highlighting the importance on-going evaluation to identify opportunities for program improvement.

Both studies focus on the impact of community screening programs, which "hold great potential today for providing data to answer questions about ways in which breast cancer screening can be made more effective and more cost effective," according to an accompanying editorial.

SOURCE:
Cancer, April 1, 2004, published online February 23, 2004