دانلود رایگان ترجمه مقاله مصرف سلنیوم و دیگر آنتی اکسیدان ها در طی پرتودرمانی سرطان پروستات (نشریه الزویر 2010)

مصرف سلنیوم و دیگر آنتی اکسیدان ها در طی پرتودرمانی سرطان پروستات: آیا چیز خوبی است؟

Ingestion of selenium and other antioxidants during prostate cancer radiotherapy: A good thing?

Summary

Radiation and many chemotherapy agents work to kill cells by inducing free radicals that damage DNA and proteins. Antioxidants such as vitamin E, β carotene, lycopene, and selenium have been associated with a reduction in cancer risk when ingested by prostate cancer patients. Selenium is a promising agent currently being evaluated as a prostate cancer prevention agent. Selenium is an essential trace element and is involved in antioxidant protection and the redox-regulation in humans. Several adverse effects of radiotherapy and chemotherapy in cancer patients have been linked to oxidative cell processes in the human body. Selenium supplementation may protect healthy tissues and reduce the side effects of treatment. Despite two decades of research into this question, no clear answer has appeared. Therefore, understanding the mechanism(s) by which dietary nutrients exert their effects in prostate carcinogenesis, may lead to the exploitation of new chemoprevention agents. A large body of epidemiological evidence, including observational, trials, and randomized controlled clinical trials, support the proposition that selenium may prevent prostate cancer in humans. These clinical studies are supported by in vitro and in vivo data using prostate cancer models. This systematic review provides the first evidence that antioxidant supplementation during chemotherapy holds potential for reducing dose-limiting toxicities. The pre-clinical and clinical evidence as to whether ingestion of supplemental selenium, in addition to radiotherapy/chemotherapy is beneficial, detrimental or neutral towards patient outcome is also discussed.

1 Introduction

Radiation therapy is an important curative treatment modality in the management of prostate cancer. Impressive progress has been made by improving the physical targeting of radiation to tumor tissue relative to increased sparing of normal tissue. This has led to enhanced PSA-free relapse rates accurately associated with decreased rectal and bladder toxicity.1 Chemotherapy (e.g. mitoxantrone or taxane) has traditionally been used for the treatment of metastatic disease, but is currently being used in neo-adjuvant protocols, either alone or in addition to hormone therapy, prior to surgery or radiotherapy.2,3

Both chemotherapy/radiotherapy lead to genotoxic stress that in turn leads to cancer cell killing through apoptosis, mitotic catastrophy, atrophy or terminal growth arrest. Therefore the relative efficacy of these treatments may be affected by the antioxidation that occurs in tumor tissues. A recent study suggested that 40– 80% of patients who were at a high-risk percentile of developing prostate cancer or who were diagnosed with prostate cancer, were taking complementary/alternative therapies, including the use of antioxidants.4

Based on pre-clinical and clinical evidences vitamin D, C, A, E and selenium may have a protective effect against prostate cancer. Hence it is possible for these agents to be part of chemopreventive strategies.5 However, these agents could alter the DNA damage produced in cancer cells during radiotherapy or chemotherapy.6 The potential interaction of antioxidants with radiotherapy, chemotherapy or hormonal therapy for prostate cancer is currently unclear and it is difficult to advise patients as to whether to consider antioxidant use during cancer treatment. This systematic review provides the first evidence that antioxi dant supplementation during chemotherapy holds potential for reducing dose-limiting toxicities. The pre-clinical and clinical evidence as to whether ingestion of supplemental selenium, in addition to radiotherapy/chemotherapy is beneficial, detrimental or neutral towards patient outcome is discussed. However, large scale trials, better designed to evaluate patients administered antioxidants relative to chemotherapy are warranted.