Screening women in their 40s can reduce breast cancer deaths by 25% in the first 10 years: Study
This important study suggests that offering mammographic screening to women from a younger age results in breast cancers being detected at an earlier and more curable stage
Screening women for breast cancer in their 40s saves lives, according to scientists. In a trial, where women were followed up for up to 23 years, the researchers found that screening women aged 40-49 led to a substantial and significant 25% reduction in breast cancer deaths in the first 10 years.
The total years of life saved from breast cancer in the intervention group was estimated as 620, corresponding to 11.5 years saved per 1,000 women invited to earlier screening. The absolute benefit remained roughly constant up to the end of follow-up, with approximately one death prevented per 1,000 women screened, reveals analysis.
“This is a very long term follow-up of a study which confirms that screening in women under 50 can save lives. The benefit is seen mostly in the first ten years, but the reduction in mortality persists in the long term at about one life saved per thousand women screened. We now screen more thoroughly and with better equipment than in the 1990s when most of the screening in this trial took place, so the benefits may be greater than we've seen in this study,” explains lead researcher Professor Stephen Duffy from the Queen Mary University of London.
Some countries have a breast cancer screening program offering mammography to women aged 50-70 years every two to three years. However, uncertainty currently exists over whether to start screening at a younger age, including whether it might lead to overdiagnosis of breast cancer. In the US, the breast cancer screening guidelines for women between 40-49 years can vary. The US Preventive Services Task Force, 2016, and the American Academy of Family Physicians recommend that the decision to start screening mammography in women before age 50 should be an individual one. The American College of Physicians suggests discussing benefits and harms with women aged 40 to 49 in good health and order screening with mammography every two years if they request it. The American Cancer Society says women ages 40 to 44 should have the choice to start annual breast cancer screening with mammograms if they wish to do so and that women aged 45 to 54 should get mammograms every year. The UK’s breast cancer screening program offers mammography to women aged 50-70 years every 3 years.
For the current research, the UK Breast Screening Age Trial randomized more than 160,000 UK women aged 39-41 to receive either annual mammography or the usual National Health Service (NHS) breast screening which starts at age 50. The researchers recruited 16,0921 women between October 14, 1990 and September 24, 1997. The team also includes experts from Tel Aviv University, Israel; King’s College London, UK; American Cancer Society, US and University of Dundee, UK, among others.
“53,883 women (33·.5%) were randomly assigned to the intervention group and 1,06,953 (66.5%) to the control group. Between randomization and February 28, 2017, women were followed up for a median of 22.8 years. We observed a significant reduction in breast cancer mortality at 10 years of follow-up, with 83 breast cancer deaths in the intervention group versus 219 in the control group. No significant reduction was observed thereafter, with 126 deaths versus 255 deaths occurring after more than 10 years of follow-up,” says the study published in The Lancet Oncology. It adds, “Reducing the lower age limit for screening from 50 to 40 years could potentially reduce breast cancer mortality.”
The authors say that more research is needed to clarify whether progress in early detection technology and treatment of breast cancer might modify the screening-related reduction in mortality in the 40-49 age group. They also did not consider the cost-effectiveness of lowering the screening age.
Commenting on the findings, Dr Imogen Locke, consultant clinical oncologist at The Royal Marsden NHS Foundation Trust says: “This important study suggests that offering mammographic screening to women from a younger age results in breast cancers being detected at an earlier and more curable stage. Diagnosing breast cancers before they cause symptoms results in less women dying from breast cancer and may also mean that women require less aggressive cancer treatment. It is critical that we detect cancer as early as possible to give us the best chance of successfully treating patients and saving their lives. The results also suggest “at worst modest overdiagnosis in this age group (40 to 49 years),” and that any overdiagnosed cancers would otherwise be diagnosed at NHS screening from 50 years of age. Therefore, screening in the age group of 40-49 years does not appear to add to overdiagnosed cases from screening at age 50 years and older, the research team concluded.