Efficacy of lycopene intake in primary prevention of prostate cancer: A systematic review of the literature and meta-analysis

OBJECTIVE: To evaluate the efficacy of lycopene intake in primary prevention of prostate cancer (PCa). METHODS: A systematic search of the literature was conducted in March 2015 and the articles published between the years 1990-2015 were reviewed. The following search terms were used: prostate cancer, prostatic neoplasm, lycopene, prevention, effectiveness and efficacy (MeSH). Publications including research in humans, written in English and whose texts were accessible were reviewed. The types of studies included were: clinical trials, cohort and case-control studies. We found 343 articles; of these, 27 were included in the systematic review. After the latter were rigorously analyzed, 23 were included in the meta-analysis using the pooled odds ratios (OR) and risk ratios (RR) of case-control and cohort studies, respectively, and their confidence intervals (95% CI), using random-effects models with Review Manager 5.2. RESULTS: Out of the 27 articles included in the systematic review, 22 were case-control and 5 were cohort studies. For the case-control studies, the total number of patients with PCa was 13,999 and the total number of controls 22,028. Cohort studies included 187,417 patients and PCa was diagnosed in 8,619 of these. The meta-analysis determined an OR = 0.94 (IC 95% 0.89-1.00) and RR = 0.9 (IC 95% 0.85-0.95) of PCa related with lycopene and/or raw or cooked tomatoes intake. CONCLUSIONS: Although our study found that there is a statistically significant inverse association between lycopene intake and PCa, the magnitude of this association is weak and comes solely from observational studies, which do not allow recommending its use as a standard of practice. High-quality randomized clinical trials are required to clarify current evidence.