By Linda Girgis, MD
Colorectal cancer is one of the most common cancers in the US, as well as around the world. Additionally, it remains one of the leading causes of cancer deaths as well. Our knowledge of this deadly disease increased exponentially in recent years and we now have screening tests and a plethora of treatment modalities. Yet, the number of deaths is still too high.
Around the world, colorectal cancer is estimated to comprise 9% of all cancers and is the third most common type of cancer. Of cancer deaths globally, it is the fourth leading cause. It appears to affect men and women equally. The developed world accounts for approximately 63% of all cases of colorectal cancer and there are large geographic differences.
In 2012, there were an estimated 1.4 million new cases of colorectal cancer diagnosed in the world. Of these cases, about 95% were adenocarcinomas. The Republic of Korea has the highest incidence with an age-standardized rate per 100,000 of 45.0. Slovakia and Hungary ranked second a third. The top fifty countries with the highest incidence can be seen in the following chart:
|Rank||Country||Age-Standardised Rate per 100,000 (World)|
|1||Korea, Republic of||45.0|
Source: Ferlay J, Soerjomataram I, Ervik M, Dikshit R, Eser S, Mathers C, Rebelo M, Parkin DM, Forman D, Bray, F. GLOBOCAN 2012 v1.1, Cancer Incidence and Mortality Worldwide: IARC CancerBase No. 11 [Internet]. Lyon, France: International Agency for Research on Cancer; 2014. Available from:http://globocan.iarc.fr, accessed on 16/01/2015.
Interestingly, the incidence of colorectal cancer in Korea has been observed to be increasing since 1999. The Korea Central Cancer Registry (KCCR) evaluated data on about 80-90% of cancer cases from more than 150 teaching hospitals across that country. It established that there was indeed a rapid increase in colorectal cancer incidence in Korea since 1999. This study also showed that the most common subsite was the rectum and represented approximately 41-51% of all colorectal cancers in Korea. Among Asian and Pacific Islanders living in the US, the rectum was found to represent 35% of colorectal cancers in this population among men. In contrast, the proximal colon was the most common subsite among white and black patients, both male and female, as well as female Asian and Pacific Islanders living in the US. However, the incidence of rectal cancer in Korea seems to be decreasing while that of other subsites increasing. In 2004, colorectal screening tests were introduced in Korea. Unfortunately, those partaking in these screening studies were initially low, with only 10-20% choosing to undergo these tests. Screening rates have now increased to just over 50%. Risk factors that may explain these statistics in Korea include increased alcohol consumption from 10.6 grams to 17.3 grams from 1999 to 2007, number of men with BMI over 25 increased from 25.1% to 35.3%, and increased in daily meat consumption from 6.6 grams to 95.1 grams.
The Czech Republic is another country that has one of the highest rates of colorectal cancer year after year. According to the 4Th European Colorectal Cancer Days Conference, almost 4,000 patients die every year in the Czech Republic due to colorectal cancer. The incidence and mortality rate both appear to be decreasing in this country. There are now estimated to be 60,000 patients living with this disease in that country. Worsening the situation there is the fact that over 50% of cases are diagnosed at advance stages of the disease. Participate in the screening program remains low, approximately 27% despite the fact that these services are fully reimbursed by public health funds. A project has been launched to privately invite all citizens to screening who have not already done so. Additionally, there are large differences in the availability of screening and treatment across this country. It has been estimated that less than 50% of colorectal cancer patients in the Czech Republic have access to targeted therapies.
In contrast, the lowest rates were found in Africa, where the diet is more based on beans and vegetables. In fact, one study that changing from a diet rich in fats and red meats to a traditional African one can reduce incidence of colon cancer. In African Americans who changed their diet as indicated, biologic markers revealed a decrease risk of disease after 2 weeks. African Americans are approximately 100 times more likely to develop colorectal cancer than rural Africans. The difference is thought to be mainly due to diet. The reverse was also observed when rural Africans were fed a westernized diet. They appeared to have an increase in risk based on biologic markers. In this study, diet seems to play a key role in the development of colorectal cancer and the fact that it is possible to change risk factors through dietary changes.
In the US, according to the CDC, over 50,000 patients died from colorectal cancer in 2103. And another 136,119 people were newly diagnosed in that same year. The incidence tends to vary by race and ethnicity as demonstrated in the charts below:
Sources: CDC’s National Program of Cancer Registries and National Cancer Institute’s Surveillance, Epidemiology, and End Results program.
The western diet and lifestyle have shown to possess many risk factors that are conducive to the development of colorectal cancer. Changeable risk factors include: being overweight or obese, physical inactivity, a diet rich in fats and red meats, smoking and heavy alcohol use. Risk factors that are not modifiable include older age, a history of colorectal polyps, a family history of colorectal cancer or adenomatous polyps, racial/ethnic background, having type 2 diabetes or an inherited genetic defect. Inherited syndromes that increase the risk of colorectal cancer include familial adenomatous polyposis, Gardner Syndrome, Lynch Syndrome, Turcot Syndrome, Peutz-Jergher’s Syndrome, and MUTHY Polyposis Syndrome.
Around the globe, colorectal cancer continues to be one of the most prevalent cancer types and responsible for one of the highest cancer mortalities. We now have effective screening programs that we have evidence prevent this disease. Yet, many people do not abide in these qguidelines and that seems to hold true throughout the world. We also know the risks factors that lead to this cancer and how we can decrease these risks through lifestyle modifications. The global medical community needs to do a better job educating patients and the general public if we want to make any impact on decreasing deaths from colorectal cancer.
About the Author
Linda Girgis MD, FAAFP is a family physician practicing in South River, New Jersey. She was voted one of the top 5 healthcare bloggers in 2016. Follow her on twitter @DrLindaMD.