Progress in the detection and management of breast cancer According to a new report, hundreds of thousands of women could have saved their lives in the last three decades.
The cumulative number of breast cancer deaths averted since 1989 is between 384,000 and 614,500, according to different mortality assumptions.
In 2018 alone, 27,083 to 45,726 breast cancer deaths were averted, with the expected breast cancer death rate reduced from 45.3% to 58.3%.
These estimates come from a study published online today in Cancer
"The message from the journal could not be clearer," said co-author Jay Baker, MD, professor of radiology and divisional head of breast imaging at Duke University in Durham, North Carolina. "The combination of early detection by screening mammography In addition, improved treatments has saved the lives of about half a million women living in the United States. "
Putting this in context, he added, "This is tantamount to saving the lives of every elderly woman in the projection living in Chicago today or saving every man, woman and child living in Wyoming."
However, it remains to be determined the extent of improvement related to screening and treatment improvement, the study being unable to differentiate the two, a- he noted.
We can not separate lives saved through early detection at screening versus improved treatments.
Dr. Jay Baker
The study analyzed data from the National Cancer Institute's SEER database (Surveillance, Epidemiology and End Results).
"This is one of the largest breast cancer databases in the United States, but unfortunately it does not contain any information to know if a patient's cancer has discovered during screening, "he said.
"Therefore, we can not separate the lives saved through early detection when screening for improved treatment," he said.
Decrease in breast cancer rates
In the United States, breast cancer mortality rates increased by 0.4% per year between 1975 and 1990, but have declined since 1990.
Breast cancer mortality rates decreased by 1.8% per year from 1990 to 1995, from 3.4% between 1995 and 1998 and 1.8% per year from 1998 to 2015, according to National Cancer statistics. Institute.
Although this latest study can not separate the contributions made by screening and treatment to this decrease in the number of breast cancer deaths, a previous study had already done so.
A study published last year in JAMA and reported at the time by Medscape Medical News examined the reduction in breast cancer mortality rates from 2000 to 2012 and reported that 63% of the overall reduction in breast cancer mortality was the result of a treatment and 37% of a screening.
Screening mammography has been a hot topic, with conflicting results regarding the absolute mortality benefit and the risk of harm. Some evidence suggests that generalization breast cancer screening may have a greater number of small, slow-growing tumors that are unlikely to cause death, without reducing the number of advanced cancers diagnosed.
For example, a 2016 analysis in the New England Journal of Medicine have reported that overdiagnosis of breast cancer by mammography is "more important than is generally recognized". Overdiagnosis was defined as a tumor detected during screening that would never have led to clinical symptoms.
Other studies have shown a benefit in terms of mortality with mammography screening, such as a large number of observed cases. study in the UK, which reported a "substantial" and statistically significant reduction in breast cancer mortality between 1991 and 2005, related to the establishment of a national breast cancer screening program.
In contrast, a Dutch study found that screening mammography over a 24-year period in women aged 50 to 74 years had little effect on reducing rates of advanced breast cancer or breast cancer mortality. The authors noted that screening greatly increased the detection of early breast cancer, ductal carcinoma in situ (DCIS) and stage I, thereby contributing to an increase in overdiagnosis rates.
However, a study as of 2014, found somewhat opposite results and concluded that a 37% decrease in the incidence of advanced breast cancer over the last three decades can be attributed to mammography. The detection of early breast cancer also increased by 48% during this period.
In an interview with Medscape Medical NewsBaker commented that mammography was controversial "but it should not be."
"Every few years, a different concern is raised about why mammography screening is not working or is a bad idea, and each of these concerns has been proven wrong," he said. . "The rate of overdiagnosis has been grossly inflated in several articles because these studies did not take into account the fact that the incidence of breast cancer has been steadily increasing by about 1% per year since at least the 1940s" .
The whole discussion of overdiagnosis should be seen in light of the fact that since the start of the screening mammogram, the breast cancer death rate in the United States has decreased by about 40%, he explained. .
"It's a statistical trick without taking into account the context – in this case, the increasing incidence of breast cancer has remained stable for decades before screening starts," he said. . "It's not reasonable to assume that the increase continues – at the same rate as before – is suddenly due to screening.That's what you have to accept to believe in generalized overdiagnosis." . "
Although screening guidelines can not be based on this single study, Baker noted that some of the publications "confirm that starting screening at age 40 and staying it as long as a woman stays in good health saves as many lives as possible. "
Details of the study
Baker and colleagues analyzed breast cancer mortality and demographics on US women aged 40 to 84 over a 30-year period.
Four different assumptions regarding baseline mortality rates (in the absence of screening mammograms and improved treatment) were used to examine differences in mortality rates reported by the SEER and rates of mortality. Underlying mortality for each age group of 5 years, multiplied by population for each age group. Group of 5 years old. SEER data was then used to estimate the annual and cumulative deaths from breast cancer that had been avoided in 2012 and 2015 and extrapolated SEER data were used to estimate deaths averted in 2018.
The analysis showed that, for a single year, the number of deaths averted ranged from 20,860 to 33,842 in 2012, from 23,703 to 39,415 in 2015 and from 27,083 to 45,726 in 2018.
The reductions in breast cancer mortality rates ranged from 38.6% to 50.5% in 2012, from 41.5% to 54.2% in 2015 and from 45.3% to 58.3% in 2018 .
The total number of breast cancer deaths averted since 1989 ranged from 237,234 to 370,402 in 2012, from 305,934 to 483,435 in 2015 and from 384,046 to 614,484 in 2018.
The experts weigh in
When asked to comment on the study, Anthony Miller, MD, professor emeritus at the Dalla Lana School of Public Health at the University of Toronto, Canada, noted that "an important neglected problem in this analysis is the almost total cessation of hormone replacement therapy HRT) and the subsequent reduction in the incidence of breast cancer and, almost certainly, mortality in the early 2000s ".
Miller believes that the effects of mammography screening for breast cancer have been overestimated. The main randomized screening trial that would have demonstrated this, he said, was the long Swedish trial in two districts, which showed a substantial absolute reduction in breast cancer mortality.
"This study had a lot of flaws, not [the] unless the reduction in breast cancer mortality reported in the group being tested is offset by an increase in all-cause mortality in this group, compared to the control group, "he said. Thus, the reduction in breast cancer mortality we have seen in the general population is largely due to improved treatment. "
Nancy Keating, MD, professor of medicine and health policy at Harvard Medical School and physician at Brigham and Women's Hospital in Boston, Massachusetts, also explained that the current paper updates earlier work treatment decreased the number of breast cancer deaths.
"But unfortunately, it does not allow us to know more precisely why mortality has decreased," she said. "I think it's a combination of screening and treatment, but we do not know how much everyone contributes, and this study does not tell us.
"This is a useful methodological document for population estimates, and even for other countries that think how to calculate deaths averted by cancer," she explained. "Not only for breast cancer but for other types of cancer."
There has also been considerable debate about the optimal age to start screening and the interval between screenings. There are variations in the guidelines, acknowledged Keating. "It would be nice to have a simple answer."
"What we know in other newspapers is that individualized screening decisions will benefit women," she said. "We see more benefits if we select women at higher risk than women at lower risk, and we also know that there are trade-offs between screening." We want to balance the pros and cons but then we need to think about the benefits and what the disadvantages are. "
Overall, she said, "integrating women's values and preferences into selection decisions makes a lot of sense".
No specific funding has been disclosed. Baker did not reveal any relevant financial relationship; Co-author Edward Hendrick acted as a paid consultant for GE Healthcare for work outside of this study. Co-author Mark A. Helvie has received grants from GE Healthcare and IBM Watson for work done outside of this study. Keating and Miller did not reveal any relevant financial relationship.
Cancer. Posted online February 11, 2019. Abstract