Mammography associated to breast cancer incidence increase with no reduction in mortality

Mammography does not “reduce breast cancer deaths”

Image of a mammography-plate
Mammography for detection of breast cancer does not reduce the number of deaths from the disease and may actually lead to overdiagnosis, according to a new study published in JAMA Internal Medicine. Image by Grant Hutchinson.

2015 Study Abstract

Screening mammography rates vary considerably by location in the United States, providing a natural opportunity to investigate the associations of screening with breast cancer incidence and mortality, which are subjects of debate.

To examine the associations between rates of modern screening mammography and the incidence of breast cancer, mortality from breast cancer, and tumor size.

Design, Setting, and Participants
An ecological study of 16 million women 40 years or older who resided in 547 counties reporting to the Surveillance, Epidemiology, and End Results cancer registries during the year 2000. Of these women, 53 207 were diagnosed with breast cancer that year and followed up for the next 10 years. The study covered the period January 1, 2000, to December 31, 2010, and the analysis was performed between April 2013 and March 2015.

Extent of screening in each county, assessed as the percentage of included women who received a screening mammogram in the prior 2 years.

Main Outcomes and Measures
Breast cancer incidence in 2000 and incidence-based breast cancer mortality during the 10-year follow-up. Incidence and mortality were calculated for each county and age adjusted to the US population.

Across US counties, there was a positive correlation between the extent of screening and breast cancer incidence (weighted r = 0.54; P < .001) but not with breast cancer mortality (weighted r = 0.00; P = .98). An absolute increase of 10 percentage points in the extent of screening was accompanied by 16% more breast cancer diagnoses (relative rate [RR], 1.16; 95% CI, 1.13-1.19) but no significant change in breast cancer deaths (RR, 1.01; 95% CI, 0.96-1.06). In an analysis stratified by tumor size, we found that more screening was strongly associated with an increased incidence of small breast cancers (≤2 cm) but not with a decreased incidence of larger breast cancers (>2 cm). An increase of 10 percentage points in screening was associated with a 25% increase in the incidence of small breast cancers (RR, 1.25; 95% CI, 1.18-1.32) and a 7% increase in the incidence of larger breast cancers (RR, 1.07; 95% CI, 1.02-1.12).

Conclusions and Relevance
When analyzed at the county level, the clearest result of mammography screening is the diagnosis of additional small cancers. Furthermore, there is no concomitant decline in the detection of larger cancers, which might explain the absence of any significant difference in the overall rate of death from the disease. Together, these findings suggest widespread overdiagnosis.

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4 thoughts on “Mammography associated to breast cancer incidence increase with no reduction in mortality”

  1. I am in favour of breast mammograph after being diagnosed the first time I had breast cancer. I examined my breast regulary bu was not prepared when I had my first mammograph. From there I was diagnosed twice and each time it was for breast cancer then a double mascectomy. Thank goodness for this test as I might have not been around today. I also took Primodos in 1974 to diagnose a pregnancy. MY son was born with multiple abnormalities to his penis, testicles, kidney damage and a serious heart defect. Was Primodos a synethic oestrogen responsible for our trauma in life.

    1. Thanks for sharing your views on this matter. We’re glad that our blog offers a platform for discussion and exchange about personal experiences of complex and difficult issues.

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