Review article: the prevention of colorectal cancer

National and subnational incidence, mortality and associated factors of colorectal cancer in China: A systematic analysis and modelling study

Background

Due to their known variation by geography and economic development, we aimed to evaluate the incidence and mortality of colorectal cancer (CRC) in China over the past decades and identify factors associated with CRC among the Chinese population to provide targeted information on disease prevention.

Methods

We conducted a systemic review and meta-analysis of epidemiolocal studies on the incidence, mortality, and associated factors of CRC among the Chinese population, extracting and synthesising data from eligible studies retrieved from seven global and Chinese databases. We pooled age-standardised incidence rates (ASIRs) and mortality rates (ASMRs) for each province, subregion, and the whole of China, and applied a joinpoint regression model and annual per cent changes (APCs) to estimate the trends of CRC incidence and mortality. We conducted random-effects meta-analyses to assess the effect estimates of identified associated risk factors.

Results

We included 493 articles; 271 provided data on CRC incidence or mortality, and 222 on associated risk factors. Overall, the ASIR of CRC in China increased from 2.75 to 19.39 (per 100 000 person-years) between 1972 and 2019 with a slowed-down growth rate (APC1 = 5.75, APC2 = 0.42), while the ASMR of CRC decreased from 12.00 to 7.95 (per 100 000 person-years) between 1974 and 2020 with a slight downward trend (APC = -0.89). We analysed 62 risk factors with synthesized data; 16 belonging to the categories of anthropometrics factors, lifestyle factors, dietary factors, personal histories and mental health conditions were graded to be associated with CRC risk among the Chinese population in the meta-analysis limited to the high-quality studies.

Conclusions

We found substantial variation of CRC burden across regions and provinces of China and identified several associated risk factors for CRC, which could help to guide the formulation of targeted disease prevention and control strategies.

Registration

PROSPERO: CRD42022346558.

Dietary fibre for the prevention of recurrent colorectal adenomas and carcinomas

BACKGROUND

This is an update of the Cochrane review published in 2002.Colorectal cancer (CRC) is a major cause of morbidity and mortality in industrialised countries. Experimental evidence has supported the hypothesis that dietary fibre may protect against the development of CRC, although epidemiologic data have been inconclusive.

OBJECTIVES

To assess the effect of dietary fibre on the recurrence of colorectal adenomatous polyps in people with a known history of adenomatous polyps and on the incidence of CRC compared to placebo. Further, to identify the reported incidence of adverse effects, such as abdominal pain or diarrhoea, that resulted from the fibre intervention.

SEARCH METHODS

We identified randomised controlled trials (RCTs) from Cochrane Colorectal Cancer's Specialised Register, CENTRAL, MEDLINE and Embase (search date, 4 April 2016). We also searched ClinicalTrials.gov and WHO International Trials Registry Platform on October 2016.

SELECTION CRITERIA

We included RCTs or quasi-RCTs. The population were those having a history of adenomatous polyps, but no previous history of CRC, and repeated visualisation of the colon/rectum after at least two-years' follow-up. Dietary fibre was the intervention. The primary outcomes were the number of participants with: 1. at least one adenoma, 2. more than one adenoma, 3. at least one adenoma greater than or equal to 1 cm, or 4. a new diagnosis of CRC. The secondary outcome was the number of adverse events.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data, assessed trial quality and resolved discrepancies by consensus. We used risk ratios (RR) and risk difference (RD) with 95% confidence intervals (CI) to measure the effect. If statistical significance was reached, we reported the number needed to treat for an additional beneficial outcome (NNTB) or harmful outcome (NNTH). We combined the study data using the fixed-effect model if it was clinically, methodologically, and statistically reasonable.

MAIN RESULTS

We included seven studies, of which five studies with 4798 participants provided data for analyses in this review. The mean ages of the participants ranged from 56 to 66 years. All participants had a history of adenomas, which had been removed to achieve a polyp-free colon at baseline. The interventions were wheat bran fibre, ispaghula husk, or a comprehensive dietary intervention with high fibre whole food sources alone or in combination. The comparators were low-fibre (2 to 3 g per day), placebo, or a regular diet. The combined data showed no statistically significant difference between the intervention and control groups for the number of participants with at least one adenoma (5 RCTs, n = 3641, RR 1.04, 95% CI 0.95 to 1.13, low-quality evidence), more than one adenoma (2 RCTs, n = 2542, RR 1.06, 95% CI 0.94 to 1.20, low-quality evidence), or at least one adenoma 1 cm or greater (4 RCTs, n = 3224, RR 0.99, 95% CI 0.82 to 1.20, low-quality evidence) at three to four years. The results on the number of participants diagnosed with colorectal cancer favoured the control group over the dietary fibre group (2 RCTS, n = 2794, RR 2.70, 95% CI 1.07 to 6.85, low-quality evidence). After 8 years of comprehensive dietary intervention, no statistically significant difference was found in the number of participants with at least one recurrent adenoma (1 RCT, n = 1905, RR 0.97, 95% CI 0.78 to 1.20), or with more than one adenoma (1 RCT, n = 1905, RR 0.89, 95% CI 0.64 to 1.24). More participants given ispaghula husk group had at least one recurrent adenoma than the control group (1 RCT, n = 376, RR 1.45, 95% CI 1.01 to 2.08). Other analyses by types of fibre intervention were not statistically significant. The overall dropout rate was over 16% in these trials with no reasons given for these losses. Sensitivity analysis incorporating these missing data shows that none of the results can be considered as robust; when the large numbers of participants lost to follow-up were assumed to have had an event or not, the results changed sufficiently to alter the conclusions that we would draw. Therefore, the reliability of the findings may have been compromised by these missing data (attrition bias) and should be interpreted with caution.

AUTHORS' CONCLUSIONS

There is a lack of evidence from existing RCTs to suggest that increased dietary fibre intake will reduce the recurrence of adenomatous polyps in those with a history of adenomatous polyps within a two to eight year period. However, these results may be unreliable and should be interpreted cautiously, not only because of the high rate of loss to follow-up, but also because adenomatous polyp is a surrogate outcome for the unobserved true endpoint CRC. Longer-term trials with higher dietary fibre levels are needed to enable confident conclusion.

Impact of Procyanidins from Different Berries on Caspase 8 Activation in Colon Cancer

Scope. The aim of this work is to identify which proapoptotic pathway is induced in human colon cancer cell lines, in contact with proanthocyanidins extracted from various berries. Methods and Results. Proanthocyanidins (Pcys) extracted from 11 berry species are monitored for proapoptotic activities on two related human colon cancer cell lines: SW480-TRAIL-sensitive and SW620-TRAIL-resistant. Apoptosis induction is monitored by cell surface phosphatidylserine (PS) detection. Lowbush blueberry extract triggers the strongest activity. When tested on the human monocytic cell line THP-1, blueberry Pcys are less effective for PS externalisation and DNA fragmentation is absent, highlighting a specificity of apoptosis induction in gut cells. In Pcys-treated gut cell lines, caspase 8 (apoptosis extrinsic pathway) but not caspase 9 (apoptosis intrinsic pathway) is activated after 3 hours through P38 phosphorylation (90 min), emphasizing the potency of lowbush blueberry Pcys to eradicate gut TRAIL-resistant cancer cells. Conclusion. We highlight here that berries Pcys, especially lowbush blueberry Pcys, are of putative interest for nutritional chemoprevention of colorectal cancer in view of their apoptosis induction in a human colorectal cancer cell lines.

Sodium butyrate induces human colon carcinoma HT-29 cell apoptosis through a mitochondrial pathway

Some tumours respond favourably to tumour necrosis factor-alpha (TNF-alpha). Despite this preferential sensitivity, resistance to TNF-alpha remains a clinical problem and more interest is now being focused on finding compounds that induce apoptosis through other pathways. Sodium butyrate (NaBt) has anti-tumour effects on colon cancer cells, inhibiting cell growth and promoting differentiation and apoptosis. In this study we investigated whether NaBt induced apoptosis in the human colon cancer cell line HT-29 and examined the intracellular mechanisms involved. Pre-incubation of cells with NaBt significantly increased apoptosis as measured by fluorescence activated cell sorter analysis and mitochondrial membrane potential determination. This effect could be blocked with the caspase inhibitors, z-VAD-fmk (pan-caspase inhibitor), z-DEVD-fmk (caspase-3 inhibitor) and z-LEHD-fmk (caspase-9 inhibitor), but not with z-IETD-fmk (caspase-8 inhibitor). Enhancement of caspase-3 and caspase-9 activities suggests that NaBt induces apoptosis via mitochondrial pathways not involving TNF-alpha.

Overexpression of heat shock factor 1 inhibits butyrate-induced differentiation in colon cancer cells

Produced by dietary fiber, butyrate is a potential chemopreventive agent against colon cancer. It stimulates proliferation of normal colonic epithelial cells but induces growth inhibition, differentiation, apoptosis, or a combination of effects in colon carcinoma cells. In this study, we used cDNA membrane arrays and real-time reverse transcriptase-polymerase chain reaction to identify stress genes that were differentially regulated by sodium butyrate (NaB) in HT 29 human colon carcinoma cells. The results indicated that a group of heat shock protein (hsp) genes were upregulated by 3 mM NaB within the first 24 hours of exposure. Because the transcription of hsp genes is under the control of heat shock factors (HSFs), we measured the effects of overexpressed HSF-1 on the responses of HT 29 cells to NaB. Overexpression of HSF-1 inhibited NaB-induced differentiation as measured by alkaline phosphatase activity and carcinoembryonic antigen expression. These results suggest that increased expression of HSFs and Hsps might render colon carcinoma cells resistant to the chemopreventive effects of butyrate.

Aged garlic extract inhibits angiogenesis and proliferation of colorectal carcinoma cells

Because colorectal cancer is likely to develop in many people at some point during their lives, prevention has become a high priority. Diet and nutrition play an important role during the multistep colon carcinogenic process. Garlic has been traditionally used as a spice and is well known for its medicinal properties; several studies have indicated its pharmacologic functions, including its anticarcinogenic properties. However, the mechanisms by which garlic can prevent colorectal cancer remain to be elucidated. This study investigated the effect of aged garlic extract (AGE) on the growth of colorectal cancer cells and their angiogenesis, which are important microenvironmental factors in carcinogenesis. AGE suppressed the proliferation of 3 different colorectal cancer cell lines-HT29, SW480, and SW620-in the same way, but its effects on the invasive activities of these 3 cell lines were different. the invasive activities of SW480 and SW620 cells were inhibited by AGE, whereas AGE had no effect on the invasive activity of Ht29 cells. The action of AGE appears to be dependent on the type of cancer cell. On the other hand, AGE enhanced the adhesion of endothelial cells to collagen and fibronectin and suppressed cell motility and invasion. AGE also inhibited the proliferation and tube formation of endothelial cells potently. These results suggest that AGE could prevent tumor formation by inhibiting angiogenesis through the suppression of endothelial cell motility, proliferation, and tube formation. AGE would be a good chemopreventive agent for colorectal cancer because of its antiproliferative action on colorectal carcinoma cells and inhibitory activity on angiogenesis.

Case-control study of use of nonsteroidal antiinflammatory drugs and glioblastoma multiforme

Evidence from epidemiologic and experimental studies suggests that use of nonsteroidal antiinflammatory drugs (NSAIDs) reduces risk of colon and breast cancer. The association between use of aspirin and other NSAIDs and risk of adult glioblastoma multiforme (GBM) was evaluated among 236 incident GBM cases and 401 population-based controls frequency-matched on age, gender, and ethnicity from the San Francisco Bay Area Adult Glioma Study. Cases (or proxies) and controls were interviewed in person between May 1997 and August 2000. Cases with self-reported GBM reported less use of at least 600 pills of all types of NSAIDs combined during the 10-year prediagnostic period than did controls (odds ratio (OR) = 0.53, 95% confidence interval (CI): 0.3, 0.8). Findings were consistent for aspirin (OR = 0.51, 95% CI: 0.3, 0.8), ibuprofen (OR = 0.41, 95% CI: 0.2, 0.8), and naproxen/other NSAIDs (OR = 0.34, 95% CI: 0.1, 0.8). GBM cases also reported less use of acetaminophen than did controls (OR = 0.51, 95% CI: 0.3, 1.0). Eliminating participants who initiated NSAID use within 2 years of diagnosis yielded similar results. These findings show an inverse association between NSAID use and GBM. Further studies are warranted to determine whether NSAIDs might be effective in the inhibition of GBM development or progression.

Modulatory influence of garlic and tomato on cyclooxygenase-2 activity, cell proliferation and apoptosis during azoxymethane induced colon carcinogenesis in rat

Preventive intervention of colorectal cancer has become essential as a major portion of the population may develop the disease at some points during their lives. Diet and nutrition play an important role during this multistep colon carcinogenic process. Inhibitory activity of aqueous suspensions of garlic and tomato, individually and in combination, were tested on azoxymethane induced colon carcinogenesis in Sprague-Dawley rats. The effect was observed on aberrant crypt foci (ACF), the preneoplastic lesion. To investigate the mechanism of action of the agents used, cell proliferation and the level of apoptosis were determined and the expression of cyclooxygenase-2 (COX-2) protein was analyzed in the colon. Following treatment, significant inhibition of the level of cell proliferation (P<0.01 in garlic; P<0.001 in tomato and P<0.001 in combination treatment group with respect to the carcinogen control group), significant induction of apoptosis (P<0.01 in garlic treated; P<0.01 in tomato treated and P<0.001 in combination treatment group with respect to the carcinogen control group) and suppression of COX-2 expression among the treated groups resulted in significant reduction in the incidences of ACF (by 45.27% in garlic, 68.24% in tomato and 71.62% in combination treatment group). The preventive effect was better when the combination of garlic and tomato was administered in comparison to the individual treatment groups, suggesting the synergistic action of garlic and tomato.

Differences in endoscopic classification of early colorectal carcinoma between China and Japan: A comparative study

AIM: To compare the differences in the endoscopic classification of early colorectal carcinoma (CRC) between Japan and China.

METHODS: Ten cases of early CRC were included in the study. After reviewing the color pictures of these cases, 5 Japanese endoscopists and 5 Chinese endoscopists made their classificatory diagnosis individually using the current Japanese classification, and indicated their findings on which the diagnosis was based.

RESULTS: Some lesions diagnosed by the Japanese endoscopists as IIa or IIa plus IIc, were classified as Is or Isp by the Chinese endoscopists. For superficial lesions consisting of elevation plus central depression, IIa plus depression, IIa plus IIc or IIc plus IIa were classified according to the ratio of elevated area/depressed area. However, international as well as interobserver difference still existed in the classification of such lesions. In addition, most Chinese endoscopists overlooked slightly depressed part on the top of a protruded lesion. Laterally spreading tumor, a special type of IIa, was identified as LST by some Japanese endoscopists.

CONCLUSION: Discrepancies on macroscopic classification for early CRC do exist between Japanese and Chinese endoscopists, which are found not only in terminology but also in recognition of some lesions. In order to develop a universal classification, it needs for international communication and cooperation.

Primary prevention: phytoprevention and chemoprevention of colorectal cancer

Considering the various stages of carcinogenesis and the numerous tumor types and available chemoprevention agents, knowledge of the etiology and the type of cancer to be treated, or possibly prevented, and understanding of the mechanisms by which agents exert their chemoprevention benefits may provide for improved strategy in designing therapeutic regimens. Because cancer usually develops over a 10- to 20-year period, it may be necessary for some agents to be provided before or early in the initiation steps of carcinogenesis to have beneficial effects. On the other hand, some agents may be more suitable for CRC prevention if provided at a later stage of carcinogenesis. Gene array, genomics, and proteomics are useful tools in advancing our understanding of the molecular events involved in carcinogenesis and in identifying markers of risk and surrogate end-points for colorectal cancer progression. These techniques may also serve for screening, identifying, and providing treatment targets for high-risk patients populations. Treatment could be developed depending on a patient's individual needs and genomic tumor profile. Clinical markers and surrogate end-points should be considered, together with molecular measurements, to more accurately assess risk. NSAIDs and COXIBs are clinically recognized as chemoprevention agents, and clinical trials evaluating their efficacy are ongoing. Treatment protocols, including dose and timing, remain to be determined, however. DFMO may best be used in combination with other chemoprevention agents. Dietary fiber and calcium supplements, as part of an overall low-fat diet, may decrease CRC risk. Long-term compliance with this regimen may be necessary to effect a beneficial outcome. Folate holds promise but needs further investigation, especially because its beneficial effects may depend on cancer type. Phytochemicals have been identified as strong candidates for use as agents to prevent colorectal cancer in cell culture and in rodent models of carcinogenesis. Their potential as chemoprevention agents must be demonstrated in clinical trials. In vitro and animal studies indicated that combination therapy may be a promising strategy over the monotherapy approach; clinical trials addressing the safety and efficacy of some combinations (DFMO/sulindac, fiber/calcium) are underway. The gastrointestinal tract and other organs are constantly exposed to a mixture of potentially toxic compounds and molecules considered favorable to health. Homeostasis between stress-mediated by toxic compounds and defensive mechanisms, is key for the maintenance of health and the prevention of disease. Whereas aggressive pharmacologic treatment may be necessary for patients at high risk for cancer, dietary supplements may be useful for populations at normal risk. The message for cancer prevention in the general population may well remain: keep a balanced healthy diet, eating a variety from all food groups, as part of a healthy lifestyle that includes moderate exercise.