Physical Activity and Liver Cancer Risk: A Systematic Review and Meta-analyses

Physical activity and cancer risk: a dose-response analysis for the Global Burden of Disease Study 2019

OBJECTIVE

Adopting a healthy lifestyle, including regular physical activity, is widely believed to decrease cancer risk. This study aimed to quantitatively establish the dose-response relationships between total physical activity and the risk of breast, colon, lung, gastric, and liver cancers.

METHODS

A systematic review and dose-response analysis were conducted using PubMed and Embase from January 1, 1980 to March 20, 2023. Prospective cohort studies that examined the association between physical activity and the risks of any of the 5 outcomes were included. The search was confined to publications in the English language with a specific focus on human studies. Physical activity is standardized by using the data from US National Health and Nutrition Examination Surveys (NHANES) and the Global Burden of Disease 2019 database.

RESULTS

A total of 98 studies, involving a combined population of 16,418,361 individuals, were included in the analysis. Among the included studies, 57 focused on breast cancer, 17 on lung cancer, 23 on colon cancer, 5 on gastric cancer, and 7 on liver cancer. Overall, elevated levels of physical activity exhibited an inverse correlation with the risk of cancer. The dose-response curve for lung cancer exhibited a non-linear pattern, with the greatest benefit risk reduction observed at 13,200 MET-minutes/week of physical activity, resulting in a 14.7% reduction in risk (relative risk 0.853, uncertainty interval 0.798 to 0.912) compared to the inactive population. In contrast, the dose-response curves for colon, gastric, breast, and liver cancers showed linear associations, indicating that heightened levels of total physical activity were consistently associated with reduced cancer risks. However, the increase in physical activity yielded a smaller risk reduction for colon and gastric cancers compared to breast and liver cancers. Compared to individuals with insufficient activity (total activity level < 600 MET-minutes/week), individuals with high levels of activity (≥ 8,000 MET-minutes/week) experienced a 10.3% (0.897, 0.860 to 0.934) risk reduction for breast cancer; 5.9% (0.941, 0.884 to 1.001) for lung cancer; 7.1% (0.929, 0.909 to 0.949) for colon cancer; 5.1% (0.949, 0.908 to 0.992) for gastric cancer; 17.1% (0.829, 0.760 to 0.903) for liver cancer.

CONCLUSIONS

This study demonstrated a significant inverse relationship between total physical activity and the risk of breast, gastric, liver, colon, and lung cancers.

Association between physical activity and digestive-system cancer: An updated systematic review and meta-analysis

BACKGROUND

Physical activity (PA) may have an impact on digestive-system cancer (DSC) by improving insulin sensitivity and anticancer immune function and by reducing the exposure of the digestive tract to carcinogens by stimulating gastrointestinal motility, thus reducing transit time. The current study aimed to determine the effect of PA on different types of DSC via a systematic review and meta-analysis.

METHODS

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched for relevant studies in PubMed, Embase, Web of Science, Cochrane Library, and China National Knowledge Infrastructure. Using a random effects model, the relationship between PA and different types of DSC was analyzed.

RESULTS

The data used for meta-analysis were derived from 161 risk estimates in 47 studies involving 5,797,768 participants and 55,162 cases. We assessed the pooled associations between high vs. low PA levels and the risk of DSC (risk ratio (RR)  = 0.82, 95% confidence interval (95%CI): 0.79-0.85), colon cancer (RR = 0.81, 95%CI: 0.76-0.87), rectal cancer (RR = 0.88, 95%CI: 0.80-0.98), colorectal cancer (RR = 0.77, 95%CI: 0.69-0.85), gallbladder cancer (RR = 0.79, 95%CI: 0.64-0.98), gastric cancer (RR = 0.83, 95%CI: 0.76-0.91), liver cancer (RR = 0.73, 0.60-0.89), oropharyngeal cancer (RR = 0.79, 95%CI: 0.72-0.87), and pancreatic cancer (RR = 0.85, 95%CI: 0.78-0.93). The findings were comparable between case-control studies (RR = 0.73, 95%CI: 0.68-0.78) and prospective cohort studies (RR = 0.88, 95%CI: 0.80-0.91). The meta-analysis of 9 studies reporting low, moderate, and high PA levels, with 17 risk estimates, showed that compared to low PA, moderate PA may also reduce the risk of DSC (RR = 0.89, 95%CI: 0.80-1.00), while compared to moderate PA, high PA seemed to slightly increase the risk of DSC, although the results were not statistically significant (RR = 1.11, 95%CI: 0.94-1.32). In addition, limited evidence from 5 studies suggested that meeting the international PA guidelines might not significantly reduce the risk of DSC (RR = 0.96, 95%CI: 0.91-1.02).

CONCLUSION

Compared to previous research, this systematic review has provided more comprehensive information about the inverse relationship between PA and DSC risk. The updated evidence from the current meta-analysis indicates that a moderate-to-high PA level is a common protective factor that can significantly lower the overall risk of DSC. However, the reduction rate for specific cancers may vary. In addition, limited evidence suggests that meeting the international PA guidelines might not significantly reduce the risk of DSC. Thus, future studies must be conducted to determine the optimal dosage, frequency, intensity, and duration of PA required to reduce DSC risk effectively.

Associations between Physical Activity and Liver Cancer Risks and Mortality: A Systematic Review and Meta-Analysis

(1) Background: The purpose of this meta-analysis was to investigate associations between physical activity (PA) and risks and mortality of liver cancer (LC) to suggest a minimum physical activity threshold to reduce LC risks and morality. (2) Methods: A database search was performed to identify relevant studies on the associations between PA and risks and mortality of LC before August 2020. The PA amounts were divided into three groups (high: ≥3 h/week, moderate: 2–3 h/week, and low: <2 h/week). The pooled relative risks of LC were calculated. (3) Results: A total of 10 prospective cohort studies were included. LC risks and mortality were 26% and 25% lower with high amounts of PA and 23% and 19% lower in moderate amounts of PA, respectively, compared to low amounts of PA. At the vigorous intensity PA level, high and moderate amounts of PA reduced the LC risk by 54% and 45%, respectively. (4) Conclusions: PA helps to reduce LC risks and mortality in a dose-dependent manner. At a minimum, two hours/week PA are mandatory to reduce LC mortality.

Physical Activity and Risk of Hepatocellular Carcinoma Among U.S. Men and Women

Mounting evidence indicates a potential beneficial effect of vigorous-intensity physical activity on hepatocellular carcinoma (HCC). However, the association between moderate-intensity physical activity, such as brisk walking, and the risk of HCC remains largely unknown. Two prospective cohorts of 77,535 women from the Nurses' Health Study and 44,540 men from the Health Professionals Follow-up Study were included. Weekly time spent on physical activities were updated biennially. The Cox proportional hazard regression model was used to calculate multivariable hazard ratios (HR) and 95% confidence intervals (95% CI). After an average 23-year follow-up, we identified 138 incident HCC cases. A higher amount of total physical activity was not significantly associated with a reduced risk of HCC (top tertile vs. bottom tertile; HR = 0.78; 95% CI, 0.51-1.18; P _trend = 0.33). For the same comparison, there was an inverse association between moderate-intensity activity and HCC risk (HR = 0.60; 95% CI, 0.38-0.94; P _trend = 0.04), whereas no statistically significant association with vigorous-intensity activity (HR = 0.88; 95% CI, 0.56-1.37; P _trend = 0.74). Engaging in brisk walking was significantly associated with a lower risk of HCC (over 1 hour/week vs. non-brisk walking; HR = 0.50; 95% CI, 0.31-0.78; P _trend = 0.006). The association between brisk walking and HCC risk was generally present across all subgroups, including age, body mass index, type 2 diabetes mellitus, smoking status, aspirin use, and alcohol consumption (all P _interaction ≥ 0.05). In conclusion, moderate-intensity activity, especially brisk walking, was associated with reduced risk of HCC among U.S. men and women. If confirmed, brisk walking might serve a feasible way for HCC prevention.

KIF15 Promotes Proliferation and Growth of Hepatocellular Carcinoma

Liver cancer is thought as the most common human malignancy worldwide, and hepatocellular carcinoma (HCC) accounts for nearly 90% liver cancer. Due to its poor early diagnosis and limited treatment, HCC has therefore become the most lethal malignant cancers in the world. Recently, molecular targeted therapies showed great promise in the treatment of HCC, and novel molecular therapeutic targets is urgently needed. KIF15 is a microtubule-dependent motor protein involved in multiple cell processes, such as cell division. Additionally, KIF15 has been reported to participate in the growth of various types of tumors; however, the relation between KIF15 and HCC is unclear. Herein, our study investigated the possible role of KIF15 on the progression of HCC and found that KIF15 has high expression in tumor samples from HCC patients. KIF15 could play a critical role in the regulation of cell proliferation of HCC, which was proved by in vitro and in vivo assays. In conclusion, this study confirmed that KIF15 could be a novel therapeutic target for the treatment of HCC.

Physical Activity and the Risk of Liver Cancer: A Systematic Review and Meta-Analysis of Prospective Studies and a Bias Analysis

BACKGROUND

Physical inactivity is an established risk factor for several cancers of the digestive system and female reproductive organs, but the evidence for liver cancers is less conclusive.

METHODS

The aim of this study was to synthesize prospective observational studies on the association of physical activity and liver cancer risk by means of a systematic review and meta-analysis. We searched Medline, Embase, and Scopus from inception to January 2019 for prospective studies investigating the association of physical activity and liver cancer risk. We calculated mean hazard ratios (HRs) and 95% confidence intervals (CIs) using a random-effects model. We quantified the extent to which an unmeasured confounder or an unaccounted selection variable could shift the mean hazard ratio to the null.

RESULTS

Fourteen prospective studies, including 6,440 liver cancers, were included in the systematic review and meta-analysis. The mean hazard ratio for high compared with low physical activity was 0.75 (95% CI = 0.63 to 0.89; 95% prediction interval = 0.52 to 1.07; I² = 64.2%). We estimated that 67.6% (95% CI = 56.6% to 78.5%) of all true effect estimates would have a hazard ratio less than 0.8. Bias analysis suggested than an unobserved confounder would have to be associated with a 1.99-fold increase in the risk of physical activity or liver cancer to explain away the observed mean hazard ratio. An unaccounted for selection variable would have to be related to exposure and endpoint with a relative risk of 1.58 to explain away the mean hazard ratio.

CONCLUSIONS

Physical activity is inversely related to the risk of liver cancer. Further studies with objectively measured physical activity and quasi-experimental designs addressing confounding are needed.