A Geography of Cancer

Study Links Higher than Expected Colorectal Cancer Mortality Rates to Poor National Health Systems

Significant global disparities exist in the screening and treatment of colorectal cancer, according to a study published last month in the journal Cancer. Using data from the International Agency for Research on Cancer and the World Health Organization (WHO), researchers used regression analysis to compare country-specific mortality-to-incidence ratios (MIR) to national health system rankings, researchers found that countries with high MIRs lack adequate cancer screening and prevention programs.

A Common and Preventable Cancer

Colorectal cancer is the third most common cancer in the world, according to World Cancer Research Fund International. Risk factors include being overweight or obese, diet (high in red and processed meats), sedentary lifestyle, excessive alcohol intake, smoking, age (over 50), and family history.

Findings from the Continuous Update Project indicate that leading healthier lifestyles that emphasize nutrition and physical activity could have prevented 47% of colorectal cancer cases.

It takes 10-15 years for the first abnormal cells to turn into colorectal cancer, according to the American Cancer Society. With regular screenings, especially colonoscopies, polyps can be detected and removed before they become cancers.

Signs and symptoms of colorectal cancer include changes in bowel habits, rectal bleeding, cramping or abdominal pain, weakness and or fatigue, and unintended weight loss.

Global Health System Rankings

MIR is calculated to determine if a country, city, or population has a higher mortality rate than might be expected given its incidence rate. It can be a useful measure of the quality of cancer care and reporting.

In the Cancer study, researchers compared data from all 34 Organization for Economic Cooperation and Development (OCED) member countries. Analyzing only OCED countries means that results may not be generalizable to lower-income developing countries but does ensure higher-quality health-related data.

Researchers compared country-specific MIRs to the WHO health system rankings, which is a weighted composite measure of 5 indices: overall health (25%), healthcare financing (25%), health inequality (25%), level of healthcare responsiveness (12.5%), and distribution of healthcare services (12.5%).

Toward a Geography of Cancer

In the last decade, the incidence of colorectal cancer has increased disproportionately in rapidly developing or newly developed countries. For instance, colorectal cancer rates among males in the Czech Republic, Japan, and Slovakia have exceeded the peak incidence rates observed in longstanding, developed nations such as New Zealand, Australia, and even the United States, which previously reported the highest colorectal cancer incidence rates worldwide.

The regression analysis revealed nine significant outliers. Iceland, Israel, Canada, and South Korea had lower MIRs than anticipated, while Chile, Greece, Poland, Mexico, and Turkey had higher MIRs than expected.

Outliers aside, the results indicate an association between weaker health systems and higher than expected MIRs.

This is no surprise to those versed in global health. The incidences of non-communicable diseases are on the rise in newly developed countries, as physical inactivity and easy access to calorically dense foods become more pervasive.

While being overweight or obese and poor diet are significant risk factors for colorectal cancer, the Cancer study’s authors suggest additional reasons for the global disparities. These factors include awareness, type and level of access to cancer screenings, and the availability of preventive treatments, such as the colonoscopy.

Approximately two-thirds of 25 countries (OCED countries, excluding outliers) have screening programs in place. This study suggests that strengthening healthcare infrastructure and increasing awareness of risks may have a significant effect on countries with higher MIRs than expected.

"The MIR appears to be a promising method to help identify global populations at risk for screenable cancers. In this capacity, it is potentially a useful tool for monitoring an important cancer outcome that informs and improves health policy at a national and international level," said Dr. Vasu Sunkara, lead author of the Cancer study.

Don’t Want to Go There?

Despite its live-saving potential, some people avoid screening for colorectal cancer because they fear the colonoscopy. If the bowel-cleansing prep doesn’t deter you, getting up-close-and-personal with your doctor may.

A non-invasive screening test, Cologuard, has just hit the market that uses molecular screening technology to detect diseases of the GI track. That’s right: non-invasive means no colonoscopy.

With Cologuard, stool DNA (sDNA) samples are collected in the home and sent to the lab. There, the DNA is isolated for testing and for detection of fecal occult hemoglobin. Methylation, mutation, and hemoglobin results are combined in the laboratory analysis to provide a positive or negative reportable result.

At this point, Cologuard requires a prescription. However, the at-home test may make screening more attractive and convenient.

Jenn Lonzer has a B.A. in English from Cleveland State University and an M.A. in Health Communication from Johns Hopkins University. Passionate about access to care and social justice issues, Jenn writes on global digital health developments, research, and trends. Follow Jenn on Twitter @jnnprater3.