Since the enactment of the National Cancer Act in 1971, the US has spent hundreds of billions of dollars in cancer research and treatment. And yet, the cancer mortality rate -- the historic benchmark of progress -- has only declined modestly while the mortality rates of other leading causes of death have declined substantially. This difference has led many to question whether we've made progress in the 'War on Cancer'. The answer is definitively yes according to Norris Cotton Cancer Center research published Monday in the Journal of Clinical Oncology.
"We have made steady progress against the burden of many cancers for decades," said principal investigator Samir Soneji, PhD, assistant professor for Geisel School of Medicine at Dartmouth and the Dartmouth Institute for Health Policy and Clinical Practice, a member of Norris Cotton Cancer Center. "As fewer and fewer people die from heart disease, stroke, and accidents, more and more people are alive long enough to be at risk of developing and dying from cancer."
Between 1970 and 2008, mortality rates from heart disease, cerebrovascular disease, and accidents declined 62 percent, 73 percent, and 38 percent, respectively. In the same period, cancer mortality rates declined just 12 percent.
According to Soneji the accuracy of existing measurements for the nation's progress against the burden of cancer are limited because they reflect progress against other diseases. Soneji and his colleagues Hiram Beltrán-Sánchez, PhD, and Harold C. Sox, MD, quantified the joint effect of cancer prevention, screening, and treatment on the burden of cancer mortality while accounting for progress against other leading causes of death.
To solve a problem first identified by the National Cancer Institute (NCI) 20 years ago, Dartmouth cancer researchers started with a metric of the burden of cancer mortality called the years of life lost due to cancer, which reflects how much longer we might expect to live in the absence of cancer. They then determined how the burden of cancer mortality directly improved from advancements in cancer care and indirectly worsened from advancements in the care of other diseases, notably cardiovascular disease.
"We estimate how the years of life lost from cancer are directly affected by cancer mortality and indirectly affected by increased cancer incidence because of greater longevity due to improvements in primary prevention, detection, and treatment of other disease," said Soneji. With this approach cancer control researchers at Norris Cotton Cancer Center were able to measure how much progress we've made against the burden of cancer mortality in America.
Soneji's research concluded that decreasing lung cancer mortality rates between 1985 and 2005 tripled their contribution to reducing the burden of lung cancer mortality. Yet not all of this progress was realized at the population level because other-cause mortality rates also decreased and the resulting increase in life expectancy and consequent change in lung cancer incidence partially offset this progress. "The decline in cigarette smoking, which began in the 1960s, is almost certainly the main reason the burden of lung cancer mortality declined," said Soneji.
Authors Soneji, Beltrán-Sánchez, and Sox also found consistent progress in reducing the burden of colorectal cancer mortality since 1985. More recent, but less consistent, progress has been made in reducing the burden on prostate and breast cancer deaths.
"Our approach reveals more accurately the aggregate contribution of cancer prevention, screening, and treatment on progress against cancer," said Soneji.
To date, survival time and mortality rates have been the leading population-level measures of cancer burden. These measures assess the effect of prevention, screening, and treatment on cancer, but they fail to account for changes in other-cause mortality rates.
Materials provided by Norris Cotton Cancer CenterDartmouth-Hitchcock Medical Center. Note: Content may be edited for style and length.
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