New study suggests benefit of screening on breast cancer deaths

June 17, 2014, British Medical Journal

Invitation to modern mammography screening may reduce deaths from breast cancer by about 28 percent, suggests a study from Norway published in BMJ. This means that for every 10,000 women invited to screening, about 27 deaths from breast cancer might be avoided during their lifetime.

An accompanying editorial says this study largely confirms what is already known - that the benefits of "are modest at best" – and calls for to be given balanced information including the harms of overdiagnosis, , and high healthcare costs.

Randomised trials from the 1970s and 80s suggested that mammography screening prevents deaths from . But the methods used by some of these studies have been criticised, and this has raised doubts about the validity of the findings. Advances in technology and treatment have also led to questions about the reliability of older trials to estimate the benefits and harms of modern day screening.

So researchers in Norway set out to evaluate the effectiveness of modern mammography screening by comparing the effects on among screened and unscreened women.

They analysed data from all women in Norway aged 50 to 79 between 1986 and 2009 – the period during which the Norwegian mammography screening programme was gradually implemented. They compared deaths from breast cancer among women who were invited to screening with those who were not invited, making a clear distinction between cases of breast cancer diagnosed before (without potential for screening effect) and after (with potential for screening effect) the first invitation for screening.

They also used a simulation model to estimate how many women aged 50-69 years would need to be invited to screening every two years to prevent one breast cancer death during their lifetime.

Based on more than 15 million person years of observation, breast cancer deaths occurred in 1,175 of the women invited to screening and in 8,996 of the women who were not invited.

After adjusting for factors such as age, area of residence, and underlying trends in breast , the researchers estimate that invitation to mammography screening was associated with a 28% reduced risk of death from breast cancer compared with not being invited to screening. The screening effect persisted, but gradually declined with time after invitations to screening ended at 70 years of age.

Using the simulation model, they also estimate that 368 women aged 50-69 would need to be invited to screening every two years to prevent one death from breast cancer during their lifetime. Further analysis to test the strength of the findings did not substantially change the results.

"In our study, the estimated benefit for breast cancer mortality (28%) associated with invitation to indicates a substantial effect," say the authors. But evolving improvements in treatment "will probably lead to a gradual reduction in the absolute benefit of screening," they conclude.

This study "adds important information to a growing body of observational evidence estimating the benefits and harms of screening," say US researchers in an accompanying editorial, and should "make us reflect on how to monitor the changing benefits and harms of breast cancer screening." They call for women to be given balanced information to help them make informed decisions about screening.

Explore further: Benefit of breast cancer screening more consistent across studies than previously understood

More information: Paper: www.bmj.com/cgi/doi/10.1136/bmj.g3701
Editorial: www.bmj.com/cgi/doi/10.1136/bmj.g3824

Related Stories

Benefit of breast cancer screening more consistent across studies than previously understood

December 11, 2013
Re-examination of data from four large studies of the benefits and harms of mammography screening shows that the benefits are more consistent across these studies than previously understood and that all the studies indicate ...

Review quantifies benefits, harms of mammography

January 5, 2014
(HealthDay)—The benefits and harms of screening mammography have been quantified in a special communication published online Dec. 30 in JAMA Internal Medicine.

Nonscreened patients with breast cancer need more treatment than screened patients

May 7, 2014
Screening 40- to 49-year-old women for breast cancer has additional benefits beyond the proven decrease in mortality rate. Patients screened with mammography are statistically less likely to undergo chemotherapy, avoiding ...

Cancer expert remains to be convinced by breast screening review

January 24, 2013
Michael Baum, Professor emeritus of surgery at University College London says that, while deaths from breast cancer may be avoided, any benefit will be more than outweighed by deaths due to the long term adverse effects of ...

Annual screening does not cut breast cancer deaths, Canadian study suggests

February 11, 2014
Annual screening in women aged 40-59 does not reduce mortality from breast cancer beyond that of physical examination or usual care, concludes a 25-year study from Canada published in BMJ today.

Mammography controversy needs greater participation to inform decisions

May 5, 2014
Doctors at the World Congress on the Menopause in Cancun, Mexico, have called for any decision to participate in mammography to be a based on an informed choice and consideration of all factors, rather than just be an automatic ...

Recommended for you

How cancer metastasis happens: Researchers reveal a key mechanism

January 18, 2018
Cancer metastasis, the migration of cells from a primary tumor to form distant tumors in the body, can be triggered by a chronic leakage of DNA within tumor cells, according to a team led by Weill Cornell Medicine and Memorial ...

Modular gene enhancer promotes leukemia and regulates effectiveness of chemotherapy

January 18, 2018
Every day, billions of new blood cells are generated in the bone marrow. The gene Myc is known to play an important role in this process, and is also known to play a role in cancer. Scientists from the German Cancer Research ...

These foods may up your odds for colon cancer

January 18, 2018
(HealthDay)—Chowing down on red meat, white bread and sugar-laden drinks might increase your long-term risk of colon cancer, a new study suggests.

The pill lowers ovarian cancer risk, even for smokers

January 18, 2018
(HealthDay)—It's known that use of the birth control pill is tied to lower odds for ovarian cancer, but new research shows the benefit extends to smokers or women who are obese.

Researchers develop swallowable test to detect pre-cancerous Barrett's esophagus

January 17, 2018
Investigators at Case Western Reserve University School of Medicine and University Hospitals Cleveland Medical Center have developed a simple, swallowable test for early detection of Barrett's esophagus that offers promise ...

Scientists zoom in to watch DNA code being read

January 17, 2018
Scientists have unveiled incredible images of how the DNA code is read and interpreted—revealing new detail about one of the fundamental processes of life.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.