Value of Screening for Breast Cancer

Two European studies published in this week's issue of THE LANCET show that the introduction of mammography screening in Sweden and The Netherlands has contributed to a decrease in deaths from breast cancer. The long-term value of mammography screening has caused considerable debate over the past few years. Laszlo Tabar from Falun Central Hospital, Sweden, and colleagues compared deaths from breast cancer in two Swedish counties 20 years before and after screening was introduced in Sweden in 1978. Their analysis included 210,000 women diagnosed with breast cancer aged 20-69 years.

Women aged 40-69 years who received screening had a 44% reduced risk of dying from breast cancer compared with women in the same age group who were diagnosed with breast cancer before screening was introduced. There was no evidence that improved treatment had a significant effect on breast cancer mortality for women younger than 40 years of age ( an age group that has never been offered screening). Women aged 40-69 years who were not screened after screening had been introduced had a 16% reduction in death from breast cancer compared with women diagnosed with breast cancer before 1978.

Laszlo Tabar comments: "Taking account of potential biases, changes in clinical practice and changes in the incidence of breast cancer, mammography screening is contributing to substantial reductions in breast cancer mortality in these two counties."

In a second study(p 1411), Harry de Koning from Erasmus Medical Centre, Rotterdam, The Netherlands, and colleagues assessed the impact of mammography screening after its roll-out in The Netherlands in the early 1990s. Deaths from breast cancer for women aged 55-74 years were around a fifth lower in 2001 compared to rates between 1986-88 (before screening programmes were introduced). Overall, the trend of increasing deaths from breast cancer in The Netherlands-which showed an increase on average of around 0.3% per year-was reversed after the implementation of screening, after which a 1.7% per year average decrease in breast-cancer deaths has occurred.