Prostate cancer chemoprevention: Current status and future prospects

Abstract

Chemoprevention is a strategy that aims to reduce the incidence and burden of cancer through the development of agents to prevent, reverse or delay the carcinogenic process. Prostate cancer is a suitable target for prevention because it has a high incidence and prevalence, as well as a long latency and disease-related mortality, and furthermore it is a disease in which lifestyle and environmental factors may play critical roles. The development of chemoprevention strategies against prostate cancer will have a huge impact, both medically and economically. Large-scale clinical trials suggest that some agents such as selenium, lycopene, soy, green tea, vitamins D and E, anti-inflammatory and inhibitors of 5α-reductase are effective in preventing prostate cancer. Although each agent has the potential to affect the natural history of the disease, it is important to develop strategies to strategically proceed for the design and selection of test agents in order to demonstrate clinical benefit with the minimum of adverse effects. Appropriate selection of agent(s), disease stage, trial design and endpoints is critical in selecting the most promising regimens to accomplish these goals. This review highlights the present status of prostate cancer chemoprevention and discusses future prospects for chemopreventive strategies that are safe and clinically beneficial.

Introduction

In recent years, cancer chemoprevention emerged as one of the major approaches for reducing cancer burden. The term ‘chemoprevention’ was first introduced by Michael B Sporn in 1976, referring to the prevention of cancer development by natural forms of vitamin A. This strategy seems to be promising for reducing cancer incidence both in well defined “high-risk” groups and also in the general population with “low-risk” of developing cancer. Chemoprevention, by definition, is a strategy for pharmacological intervention with naturally occurring and/or synthetic compounds that may prevent, inhibit or reverse carcinogenesis or suppress the development of invasive cancer (Sporn and Suh, 2002). The expanded definition of cancer chemoprevention is to inhibit or delay the development of neoplasia by blocking neoplastic inception as well as reversing the progression of transformed cells before the appearance of malignant lesions (Shukla and Gupta, 2005). In recent years, cancer chemoprevention has matured substantially and has been increasingly recognized by National Cancer Institute (NCI) prevention branch, American Society of Clinical Oncology (ASCO), American Cancer Society (ACS), American Association for Cancer Research (AACR) and some private foundations such as American Institute for Cancer Research (AICR) and Cancer Research and Prevention Foundation (CRPF). The development of chemopreventive agents is the major objective of the Chemoprevention Branch of the Division of Cancer Prevention (DCP) at NCI. The NCI-DCP aims to develop and implement research through clinical trials, screening and testing of new agents and identification of surrogate endpoint markers or cancer incidence reduction. The NCI also supports small- and large-scale clinical trials for this purpose. The overall goals of these programs are to achieve reduction in cancer incidence and mortality as well as to improve the quality of life in high- and low-risk individuals.