Is There a Benefit From Lycopene Supplementation in Men With Prostate Cancer? A Systematic Review

F Haseen; MM Cantwell; JM O'Sullivan; LJ Murray

Disclosures

Prostate Cancer Prostatic Dis. 2009;12(4):316–324 

In This Article

Abstract and Introduction

Abstract

Lycopene has a chemopreventive effect against prostate cancer but its role in prostate cancer progression is unknown; many patients increase their intake of lycopene, although there are no evidence-based guidelines to suggest an effect. Our objective was to conduct a systematic review of literature to evaluate the association between lycopene intake and prostate cancer progression. MEDLINE, EMBASE CINAHL Plus, Web of Science, AMED and CENTRAL databases were systematically searched using terms for lycopene and prostate cancer progression to identify studies published before January 2009. Eight intervention studies were identified (five with no control group; one with an unmatched control group; and two randomized controlled trials (RCTs)). An inverse association was observed between lycopene intake and PSA levels in six studies. The rates of progression measured by bone scan in one RCT were lower in the intervention group. Lycopene resulted in lowering cancer-related symptoms (pain, urinary tract symptoms), and severe toxicity or intolerance was not evident. However, the evidence available to date is insufficient to draw a firm conclusion with respect to lycopene supplementation in prostate cancer patients and larger RCTs are required in broader patient groups.

Introduction

Approximately one-third of men with prostate cancer take some form of dietary supplementation after diagnosis.[1–3] Factors associated with a higher utilization of supplements among prostate cancer patients include higher income, being better educated and following a healthy lifestyle, having more advanced or progressive disease, a lower quality of life, presence of comorbid conditions and a lower satisfaction with treatment and health status.[3–6] Patients often take supplements without a full awareness of the scientific evidence related to cancer prevention or prognosis, and the majority of patients use supplements without informing their doctors.[3,7] Furthermore, as these supplements are not conventional therapies, many health professionals are unfamiliar with their effects and may feel unqualified to provide advice to their patients with regard to their use. Undisclosed use of dietary supplements may interfere with conventional cancer treatment and cause potentially dangerous side effects (that is, toxicity, increased risk of cancer) as reported with excessive use of calcium,[8] selenium,[9] β-carotene[8] and zinc.[10] To date, there is little scientific evidence to support a role of nutritional supplementation in the prevention or reduction of prostate cancer progression.

Lycopene, a carotenoid found in high quantities in tomatoes and tomato-rich products, has been explored in relation to the prevention and treatment of various kinds of cancers.[11] High lycopene intake or high plasma lycopene concentrations have been associated with a lower risk of prostate cancer.[8,12,13] However, the majority of epidemiological research has focused on tomato or tomato products as a source of lycopene, whereas very little research has targeted other carotenoids or phytochemicals found in tomatoes. Although lycopene seems to be the bioactive compound of major importance, there is also the possibility of a synergistic action with other compounds in tomato, especially glycoalkaloids (tomatine), phenolic compounds (quercetin, kaempferol, naringenin and chlorogenic acid), salicylates and carotenoids, other than lycopene (phytoene and phytofluene), which cannot be excluded. Lycopene is a potent antioxidant and possible mechanisms by which lycopene may prevent cancer may include (i) inhibition of growth and induction of differentiation in prostate cancer cells;[14–17] (ii) upregulation of tumor suppressor proteins and increased gap-junctional intercellular communication;[18,19] and (iii) prevention of oxidative DNA damage.[20,21]

Although lycopene intake before diagnosis has been linked to reduced prostate cancer risk, there are limited data on the impact of post-diagnostic diet or supplementation and progression of prostate cancer. Nutrients that apparently protect against cancer development may continue to have an anticarcinogenic effect after diagnosis and slow disease progression.[22,23] A study examined post-diagnostic diet and risk of prostate cancer progression in prostate cancer patients from the Health Professionals Follow-up Study and showed that a higher post-diagnostic consumption of tomato sauce was associated with a substantial decrease in the risk of cancer progression: an increase of one serving of tomato sauce per day was associated with an approximately 50% lower risk of progression (measured by rising PSA levels, or metastasis to lymph nodes, bones or other organs).[24] However, recommendations regarding the use of lycopene supplementation in prostate cancer patients require evidence from experimental studies, rather than from observational studies, and ideally from a systematic review/meta-analysis of the evidence from experimental studies. Recently, a review has been conducted to identify the effect of diet and dietary supplementation on prostate cancer progression, recurrence and survival,[25] in which lycopene supplementation was discussed along with other nutritional supplements and prostate cancer. Results from randomized controlled trials (RCTs) showed no benefit in terms of PSA or PSA doubling time with lycopene supplementation alone or with lycopene combined with other agents including soy isoflavones. However, another important aspect of nutritional supplementation was not considered in this review, that is, intervention-related side effects, or toxicity as a result of supplementation. We therefore conducted a systematic review of all available experimental evidence relating to lycopene supplementation and prostate cancer progression to provide evidence-based recommendations for patients with prostate cancer.

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