Abstract
The associations between red and processed meat consumption and the risk of colorectal cancer types have not been conclusively defined. We performed a systematic review and meta-analysis to analyze these associations. We searched PubMed and EMBASE to identify studies published from inception through September 2016. Dose-response, subgroup and subtype analyses of colorectal cancer (colon cancer, proximal colon cancer, distal colon cancer and rectal cancer) were performed. We ultimately selected 60 eligible studies. Positive associations were observed for colorectal cancer in case-control studies (red meat, P<0.01; processed meat, P<0.01) and cohort studies (red meat, P<0.01; processed meat, P<0.01). However, subtype analyses yielded null results for distal colon cancer in case-control studies (P=0.41) and cohort studies (P=0.18) for red meat and null results for proximal colon cancer in case-control studies (P=0.13) and cohort studies (P=0.39) for processed meat. Additionally, although the results of case-control studies were positive (red meat, P<0.01; processed meat, P=0.04) for rectal cancer, there were no positive associations between red (P=0.34) and processed meat (P=0.06) consumption and the risk in cohort studies. In a systematic review and meta-analysis, we found consumption of red and processed meat was associated with the risk of overall colorectal cancer but not rectal cancer. Additionally, there were no associations between the consumption of red meat and distal colon cancer risk and between the consumption of processed meat and proximal colon cancer risk.
Highlights
According to GLOBOCAN 2012, colorectal cancer (CRC) is the second most frequently diagnosed cancer in females and the third most frequent in males, with an estimated 693,900 deaths worldwide each year [1]
There were no associations between the consumption of red meat and distal colon cancer risk and between the consumption of processed meat and proximal colon cancer risk
The continuously updated report from the World Cancer Research Fund (WCRF, which is based on prospective studies published through 2010) on CRC judged the evidence for the role of red meat and processed meat to be “convincing”, there was insufficient independent evidence on proximal colon cancer (PCC), distal colon cancer (DCC) and rectal cancer (RC)
Summary
According to GLOBOCAN 2012, colorectal cancer (CRC) is the second most frequently diagnosed cancer in females and the third most frequent in males, with an estimated 693,900 deaths worldwide each year [1]. Considering the increasing trend in the incidence and the high fatality, there is an urgent need to find novel strategies to prevent CRC. When cooked at high temperature for a long time, red and processed meats are a major source of carcinogens, including polycyclic aromatic hydrocarbons, heterocyclic amines and N-nitroso compounds, which may play a role in the development of CRC [4, 5]. The continuously updated report from the World Cancer Research Fund (WCRF, which is based on prospective studies published through 2010) on CRC judged the evidence for the role of red meat and processed meat to be “convincing” (http://wcrf.org/int/research-we-fund/ continuous-update-project-findings-reports/colorectalbowel-cancer), there was insufficient independent evidence on proximal colon cancer (PCC), distal colon cancer (DCC) and rectal cancer (RC). Many high quality www.impactjournals.com/oncotarget studies have been published in recent years and an updated meta-analysis of the literature will likely clarify the impact of these recent studies
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