Cancer Rates Fall in Richer Nations, Rise in Poorer Ones

Issue 27 Summer/Fall 2016

There has been a tremendous shift in worldwide cancer rates since the 1990s. As lower income countries become more prosperous, cancer death rates - the number of cancer deaths per 100,000 persons - are rising. Conversely, cancer death rates in high income countries are declining. These figures are, of course, adjusted for changes in age and gender distribution.

Dana Hashim, MD and Paolo Boffetta, MD

Dana Hashim, MD and Paolo Boffetta, MD

Reasons for these patterns must be understood in light of their contexts. Cancer death rates are determined by three main factors: exposure to risk factors, accessibility to early detection and screening, and the availability of effective treatment.

Studies show that deaths from most common cancers, including breast, prostate, colorectal, and cervical cancers, are approaching comparable levels in higherand lower-income countries.

However, longer life expectancy and urbanized lifestyles in Latin America, Asia, and the Middle East/North Africa are causing a concurrent rise in cancer risk factors. Individuals in these countries are moving away from the rural lifestyles of previous generations in favor of easier food and work accessibility offered by urban life. The need for physical activity is lessened, and diet becomes high in processed foods and low in fruits and vegetables, which are risk factors for several cancers.

Similarly, obesity and lack of physical activity are risk factors for breast and colorectal cancers. As individuals in lower-income countries adopt the risk behaviors of higher-income countries, their cancer incidence rates and, subsequently, their cancer mortality rates, increase. Because many of these same cancer risk factors continue to persist in high-income populations, the decline in cancer death rates in regions such as North America and Europe has been slow.

The past few decades have seen nationwide screening plans for cancers of the breast, colorectum, and cervix established in high-income countries. This has translated into a widening gap between the incidence and the mortality rates.

In high-income countries, this gap is due to the early detection of cancer cases at a time when treatment can be the most effective. For lower-income countries, in which fewer individuals have access to cancer screening, the gap between rates of cancer deaths and rates of newly diagnosed cases is less apparent, and most patients with cancer will still die of their disease.

Great strides have been made in the treatment for prostate, colorectal, breast, and cervical cancers to effectively reduce death rates. However, the most cutting-edge cancer treatments are primarily available in countries rich in medical resources and expertise.

Although cancer risk factors are increasing in lower-income countries and people are living longer, medical supplies, medications, and specialists are still inaccessible, especially for patients in rural areas.

Liver cancer is an example of a cancer with few known effective treatments and no screening methods for early stage detection. Liver cancer death rates are rising in most regions. This increase is due to the increasing occurrence of hepatitis infection in lowerincome countries, but also in highincome countries due to unprotected sexual intercourse, needle sharing, and pre-1992 blood transfusions.

The recent development of effective treatment of HCV infection will hopefully impact on the incidence of liver cancer; for the time being, however, to reduce liver cancer death rates, more research needs to be done on ways to identify the cancer early and cure it before it spreads.

Thanks to better public awareness and laws discouraging smoking, lung cancer is declining in men in both lowand high-income countries. Unfortunately, as women in many countries in Asia and Europe adopted the smoking patterns of men towards the end of the 20th century, a rising trend in female lung cancer is apparent in many countries. Because most lung cancers are detected at advanced stages, most are incurable.

These deaths are potentially avoidable through smoking-cessation programs, but also more research is needed on curative lung cancer treatment and screening methods to identify and treat lung cancer before it reaches a fatal stage.

The available data can tell only part of the story. Recorded cancer cases and deaths are available for only less than half of the world’s population. Even for countries with some data, causes of death are not accurately and consistently recorded.

Unfortunately, this is the situation for most low-income countries due to a lack of resources and expertise. Some studies have used mathematical models to attempt to capture missing deaths, but these methods have practical limitations and the true cancer experiences of millions of people remain unknown, thus limiting efforts for cancer prevention and control.

An important component of any program aimed at tackling the growing number of cancer deaths in lowerincome countries must involve cancer registry program standardization, including systematic reporting of cancers, accurate population counting, and active follow-up.

At the same time, much work is needed to reduce cancer deaths by encouraging more research and reducing cancer risk factors, especially for high-fatality cancers, such as liver cancer, stomach cancer and lung cancer.