Learning from East to West and vice versa: Clinical epidemiology of colorectal cancer in China

Abstract

Cancer continues to be a significant health problem in China, and there is increasing interest in studies on cancer in China in the peer-reviewed English-language literature. An example is the recent special issue Breast Cancer in China in this journal. The current issue offers another interesting report on cancer in China, this time on the clinical epidemiology of colorectal cancer. In this issue of Cancer, Shi and colleagues describe the design and baseline characteristics of a cohort of 8465 patients who were diagnosed with primary colorectal cancer from 2005 through 2014 at 13 tertiary hospitals in 9 provinces across China. The authors collected information on sociodemographic characteristics, diagnosis, treatment, and health care costs. The article reports several time trends that are interesting, but it also provides a preview of potential future articles that could come out of this cohort. For example, the time trends illustrated in their Figure 1 indicate that, among this cohort of patients with colorectal cancer, rectal cancer continues to be more prevalent than colon cancer. Interestingly, in Western countries, colon cancer is more prevalent than rectal cancer, and one could speculate about the differences between countries that may explain differences in cancer rates. Perhaps even more interesting, however, is that, as indicated in their Figure 1, although colon cancer continues to be more prevalent than rectal cancer, over time, these 2 lines start to converge. Apart from changes in clinical care, screening, and treatment, changes in lifestyle factors may partly explain these shifts over time because the data indicate that associations of lifestyle and colorectal cancer may differ according to the anatomic subsite of the cancer. In recent decades, China’s economic development has resulted in large transitions in the lifestyle and diet of the Chinese population, in which traditional Chinese diets, characterized by grains and vegetables, are being displaced by diets containing more meat and more energy-dense foods. Although Shi et al did not collect lifestyle information and focused mainly on clinical characteristics, they did provide some insight into potential changes in lifestyle by presenting information on obesity rates using body mass index (BMI) data. As a result of China’s continued economic development and changes in the Chinese diet, there was an increase in the obesity rate. That increase in BMI over time was also observed over time in the current cohort. Because obesity is a clear risk factor for colorectal cancer in Western countries, and, in those countries, colon cancer is more prevalent than rectal cancer, it would be interesting to study whether changing obesity rates can partly explain why rectal cancer seems to drop, while colon cancer seems to increase. Another interesting lead would be to look into regional differences between BMI and trends in colon versus rectal cancer and other clinical characteristics. Such studies can provide inspiration for tailored lifestyle interventions in the population that may help to decrease obesity rates in China and, consequently, the incidence of (colorectal) cancer. Those tailored interventions not only should focus on BMI but also should promote being more physically active, higher intake of foods high with dietary fiber, and lower intake of red and processed meat because those lifestyle factors convincingly lower the risk of colorectal cancer. Moreover, higher levels of vitamin D clearly are associated with a lower risk of colorectal cancer, although evidence from intervention studies to support a causal relation is not fully conclusive. Because the prevalence of vitamin D deficiencies in China is high (higher than, eg, in the United States), further research into the potential effect of vitamin D interventions on cancer risk in China is highly relevant and important. Another interesting avenue for further investigation would be to assess body composition in this cohort of patients with colorectal cancer. Over the last 2 decades, researchers have started to use diagnostic computed tomography (CT) images to obtain information on body composition. Through the opportunistic use of those images, distinct features of body composition can be quantified in this patient population. Cross-sectional areas of skeletal muscle and adipose tissue,