Plain language summary
Prostate cancer (PCa) is a leading cause of morbidity and mortality. Nutrition, in particular adopting a western lifestyle, is thought to be an important contributor to prostate carcinogenesis. The primary role of insulin-like growth factor (IGF) ligands (IGF-I, IGF-II) is to regulate prenatal and postnatal growth with binding proteins modulating their action. The aim of this study was to investigate the influence of lycopene or green tea on circulating IGF peptides in men at elevated risk of PCa. The ProDiet trial was nested within the Prostate testing for Cancer and Treatment trial of treatments for localised PCa for men aged 50–69 years. Participants were randomly assigned to receive one of three lycopene interventions: lycopene-rich diet, lycopene capsules or matched placebo capsules and one of the green tea interventions: green tea drink, green tea-derived capsules or matched placebo capsules. Results indicate that increased tomato intake, lycopene supplementation, green tea drink or green tea supplementation did not influence the measured IGF ligands. Authors conclude that their study did not provide clear evidence that lycopene or green tea supplementation may influence serum levels of IGF which may contribute to the increased risk of PCa in men.
Abstract
Whether prostate cancer (PCa) may be preventable by dietary interventions can be assessed in randomized trials using intermediate biomarkers of cancer risk or progression. We investigated whether lycopene or green tea modify circulating insulin-like growth factor (IGF) peptides in men at increased risk of PCa. Participants (aged 50-69 years) in one centre in the UK wide PCa testing and treatment trial (ProtecT) with prostate specific antigen between 2.0 and 2.95 ng/ml or negative biopsies, were randomized to daily lycopene (n = 44 assigned 15 mg capsules/day; 44 assigned a lycopene-rich diet; 45 assigned placebo) and green tea (n = 45 assigned 600 mg/day epigallocatechin gallate; 45 assigned green tea drink; 43 assigned placebo) for 6 months. The interventions significantly elevated the primary outcomes, serum epigallocatechin gallate and lycopene at 6 months of follow-up. We report here an exploratory analysis in which serum IGF-I, IGF-II, IGF binding protein (BP)-2 and IGFBP-3 were measured at baseline and 6 months of postintervention. A total of 133 men were randomized (34% of eligible men approached) and 130 had follow-up IGF peptides (98%). In intention-to-treat analyses, there was only weak evidence that lycopene or green tea influenced some aspects of serum IGF-I, IGF-II, IGFBP-2 or IGFBP-3. In men randomized to lycopene supplements, IGFBP-2 was nonsignificantly (50.9 ng/ml; 95% confidence interval: -51.2-152.9, P = 0.3) higher in comparison to placebo, whereas in men randomized to green tea supplements, IGFBP-3 was nonsignificantly (205.2 ng/ml; 95% confidence interval: -583.3-172.9, P = 0.3) lower than with placebo. In this small, pilot randomized controlled trial, there was little evidence that lycopene or green tea interventions influenced serum levels of IGF-I, IGF-II, IGFBBP-3 and IGFBP-2. However, the effects were imprecisely estimates and some observed trends may justify larger trials.
Methodological quality
Jadad score
:
4
Allocation concealment
:
Yes
