Systematic Review Of The Relationship Between Folate Supplementation And Cancer Risk

Purpose: To evaluate systematically the effect of folic acid supplementation on the incidence of cancerMethod: The computer systems were used to search the databases of China Knowledge Network,Wanfang,Weipu,Cochrane library,Embase,Pubmed,and t he websites of clinical trials.The retrieval time was updated to January 2018.Al l randomized controlled trials(RCTs)of effects of folic acid ? 0.4 mg/d on the incidence of cancer were screened.The Cochrane Collaboration Network-biased risk assessment tool was used to evaluate the data quality of the included litera t-ure.Data were extracted using the excel table.Data analysis was performed usi-ng Stata 14.0 software.Results: Eleven studies with a total of 62,108 subjects were eventually included into the systematic review.(1)For the types of the cancer,folic acid supplementation had no statistically significant difference on the incidence of total cancers(n=62108,RR=1.07,95%CI: 0.97~1.17,P=0.165),and the incidence of individual cancer including colorectal cancer(n=46604,RR=0.95,95%CI: 0.61~1.48,P=0.828),lung cancer(n=44723,RR=1.24,95%CI: 0.96~1.60,P=0.093),breast cancer(n=37525,RR=0.82,95% CI: 0.63~1.06,P=0.125),prostate cancer(n=16306,RR=0.74,95%CI: 0.41 to 1.32,P=0.307),hematologic malignancies(n=29971,RR=0.98,95%CI: 0.76 to 1.27,P=0.897).(2)For the participants who had a history of colorectal adenoma,cardiovascular diseases or preexisting cardiovascular diseases,folic acid supplementation had no statistically significant difference on the incidence of total cancers(n=58576,RR=1.06,95%CI:0.97~1.17,P=0.199).(3)With folic acid alone,folic acid supplementation had no statistically significant difference on total incidence of cancers(n=1532,RR=0.99,95%CI:0.58~1.67,P=0.967).When used in combination with vitamin B,folic acid supplementation had no statistically significant difference on the incidence of total cancers(n=37914,RR=1.07,95%CI:0.96~1.69,P=0.20).When used in combination with other drugs,folic acid supplementation had no statistically significant difference on theincidence of total cancers(n=20272,RR=1.00,95%CI:0.77~1.29,P=0.996).Whe n used in combination with aspirin,folic acid supplementation had statistically si g-nificant difference on the incidence of total cancers(n=1960,RR=1.43,95%CI:1.00~2.03,P=0.047).(4)When the follow-up?5 years,folic acid supplementation had statistically significant difference on the incidence of total cancers(n=28537,RR=1.10,95%CI:1.01~1.20,P=0.034),while the result was opposite when t hefollow-up time was less than 5 years.Conclusion: The systematic review showed that there was no statistically significant difference on the incidence of total cancers and individual cancer including colorectal cancer,lung cancer,breast cancer,prostate cancer,and hematological malignancies between the folate test group with ? 0.4 mg/d and the control group.Participants who had a history of colorectal adenoma,cardiovascular disease or preexisting cardiovascular diseases,the results showed no statistically significant difference on the incidence of total cancers between the folate test group and the control group.But when folate was used in combination with aspirin,or when the follow-up?5 years,the incidence of total cancers was increased moderately.