Breast cancer mortality after implementation of screening in Norway
Published: December 18, 2019
The new study is based on registry data from about 1.3 million women from all over Norway in the period 1977 to 2014. This makes the study the largest of its kind, not only in Norway, but also internationally.
- The results show that the introduction of BreastScreen Norway has reduced breast cancer mortality among women who are offered the opportunity to participate by about 20 percent. In addition, improved breast cancer treatment has led to a further reduction of more than 20 percent, says the researcher responsible for the study, Solveig Hofvind of the Cancer Registry of Norway.
BreastScreen Norway is a public and voluntary offer of mammography screening every two years for women 50 to 69 years. The program aim at reducing breast cancer mortality by detecting the disease early, when the prognosis is better and the opportunities for more gentle treatment are more likely.
- The effect of mammography screening has been debated, but a significant majority of the studies show a marked reduction in breast cancer mortality after the introduction of screening, Hofvind states.
Screening and improved breast cancer treatment in equally important
According to Hofvind, a major challenge in previous studies has been to distinguish between the effect of the screening itself and the fact that breast cancer treatment has been improved significantly over the recent years.
She explains that in this study the researchers were able to differentiate the effects of treatment and screening because of the high quality of data combined with the long follow-up time in the study.
- We are fortunate enough to have access to an excellent data base with individual data from the National Population Register, the Cause of Death Register and the Cancer Registry of Norway, and in combination with the long follow-up time, this becomes a powerful study, she says.
Hofvind points out that the method is robust and shows a clear effect. However, the also reveal the need for further studies.
- We now want to proceed with investigating several factors related to treatment, but also the effect of actually participating in the screening program, she says.
Most effective among the youngest
- We found that the effect of the mammography screening was most apparent among the youngest women, that is women aged 50 to 59, says Hofvind.
The results of the study are consistent with other comparable studies, she adds, including one from Denmark earlier this year, which also showed a 20 percent reduction in breast cancer mortality due to organized mammography screening.