Cancer deaths are improving, but a cure remains distant

Originally published in MedPage Today

by Joyce Frieden, MedPage Today News Editor

Almost 40 years and 100 billion federal dollars have been invested in the “War On Cancer” since President Richard M. Nixon declared it, but the campaign is far from over, two researchers concluded this week in the Journal of the American Medical Association.

“These funds have been more than matched by research investments from pharmaceutical companies, nongovernmental organizations, and states, Susan Gapstur, PhD, MPH, and Michael Thun, MD, both of the American Cancer Society, noted in a commentary that accompanied a wide-ranging Mar. 17 issue on cancer.

“However,” they wrote, “the total spending on cancer research is dwarfed by the medical and social costs resulting from the more than 100 diseases that are collectively called cancer.”

Although some critics complain about the relatively slow progress of the fight against cancer compared to other health threats, such as cardiovascular disease, the authors argued that comparing cancer rates in the U.S. at any two time points “can be misleading.”

Such comparisons should “take into account the more than 30% increase in the U.S. population that has occurred since 1970, and the nearly 2-fold increase in the proportion of adults aged 55 years or older, who account for more than 75% of all incident cancers,” they wrote.

In a way, they argued, this is good news, since it reflects progress in increasing life expectancy.

“As life expectancy has increased, the lifetime risk of being diagnosed with cancer has increased as well,” Gapstur and Thun wrote. “Nearly 1 in 2 men and more than 1 in 3 women will be diagnosed with cancer given the current lifespan.”

Cancer is currently the second leading cause of death in the U.S. and will overtake ischemic heart disease as the leading cause of death worldwide if current trends continue.

“Internationally, the increasing numbers and aging of populations, in conjunction with the dissemination of Western patterns of smoking, diet, and physical inactivity, are already creating a global health crisis for many chronic diseases, including cancer, in low- and medium-resource countries,” the authors observed.

One of the problems with curing cancer, they wrote, is that it is a very complex disease — far more so than scientists predicted in 1971.

Cancer not only comprises more than 100 different anatomical and histological subtypes, but also exists in multiple molecular variants, with different prognoses and clinical features, the writers noted.

“The inherent genetic instability of cancers allows them to change rapidly and generate clones that are resistant to treatment,” they declared. “Indeed, many cancers are masters of disguise, camouflaged from host defenses.”

Over time, it has become clear that there will be no single, “silver bullet” to win the war on cancer.

“Instead, it is essential to more forward on multiple fronts simultaneously, addressing the entire spectrum from primary prevention to early detection, treatment, and palliation,” the authors concluded.

One area where significant progress has been made is in primary prevention — largely through the reduction of cigarette smoking in the U.S. The resulting decrease in lung cancer mortality accounted for nearly 40% of the reduction in the overall cancer death rate in men between 1990 and 2006.

On the other hand, “the epidemic of overweight and obesity — which is associated with the incidence of many types of cancer — during the past two decades in the United States has created a new public health challenge,” though its effects on cancer incidence are unclear, Gapstur and Thun wrote.

Early detection also has been successful in the control of breast and colorectal cancer, but the challenge of improving early detection remains.

In terms of treatment, “remarkable” progress has been made with childhood cancers, Hodgkin disease, testicular cancer and chronic myelogenous leukemia, the authors wrote. Progress also has been made in more common cancers such as breast, colorectal, and prostate cancer.

Although the prognosis for most cancers is excellent if they are localized when diagnosed, “metastases remain a critical problem, as do certain highly lethal cancers (pancreas, liver, ovary, lung, brain) that remain refractory to current therapies,” they said.

On the whole, however, “advances and insights accumulated during the last 40 years provide a strong foundation on which to continue the fight against cancer,” the authors concluded.

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