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  • br The immunoassay technique has the important advantages of


    The immunoassay technique has the important advantages of being simple, inexpensive, and highly sensitive, and has attracted great attention in the field of diagnosis and screening of cancer. Several commonly used serum diagnostic biomarkers play an important role in the diagnosis of different types of cancer, including cancer antigen (CA) 15-3 and carcinoembryonic antigen (CEA) in BC. However, little attention has been paid to their ability to differentiate between BC and benign breast lesions.
    The increasing production rate of reactive oxygen species leads to many modifications in the nucleotide base of DNA. These oxidative modifications produce several base lesion substances.4 Guanine base has the lowest oxidation potential compared with other bases. Therefore, the guanine residues are more susceptible to free radical attack, resulting in the formation of 8-hydroxy-2’-deoxyguanosine (8-OHdG). 8-OHdG has received greater attention from scientific researchers and is commonly selected as a biomarker of oxidative stress indicating DNA damage. This DNA damage lesion (8-OHdG residues) produces transversion-mutation by pairing with SPDP or cytosine in the replication process (GC to TA).5 This mutation type was considered the second major somatic mutation expressed in human cancers. Therefore, the presence of 8-OHdG in cells indicates the ability of mutagenesis and increases the possibility of carcinogenesis.5 Permanent oxidative stress lesions lead to cancer.6 Previously, 8-OHdG was greatly evaluated in animal and human models in both cells and tissues.6-8 8-OHdG has been used widely in many studies, not only as a biomarker for the measurement of endogenous oxidative DNA damage, but also as a risk factor for many diseases, including cancer.9
    The levels of 8-OHdG were highly determined in BC cells and tissues compared with normal cell lines and tissue. Significantly higher levels of 8-OHdG in both cells and tissues of BC were found compared with those of noncancerous breast.6 Similarly, the blood levels of 8-OHdG in patients with BC increased compared with healthy controls.8 This interesting evidence encouraged us to propose that 8-OHdG as a biomarker of DNA damage owing to oxidative stress can be an effective discrimina-tory biomarker in the early detection and determination of people at a high risk of cancer to assist in the screening approach, treatment, and prognosis of BC.
    The common tumor markers CEA and CA15-3 have been given much attention in recent years as prognostic factors of BC.10 The levels of preoperative CEA and CA15-3 serve as a good confirma-tory indicator for oncologists for the diagnosis and the selection of the proper treatment of BC.11,12 In 2005, the European Group on Tumor Markers has recommended using the levels of both markers CEA and CA15-3 in the evaluation of prognosis, early detection, and treatment of patients with BC.13 In 2007, the guidelines of the American Society of Clinical Oncology (ASCO) stated that they “do not recommend the use of serum CA 15-3 and CEA for or screening, diagnosis, staging, or routine surveillance of patients with BC after primary therapy.”14
    Previous work has shown that 8-OHdG levels were high in urine samples of patients with BC compared with control groups.15-17 In addition, other groups studied the role of 8-OHdG in BC and found that the levels were higher in patients with BC.16 However,  Essam Eldin Mohamed Nour Eldin et al
    its diagnostic role at different stages of BC has not been investigated previously; therefore, there is a rationale to assess the levels of 8-OHdG in patients with BC at different stages of the disease.
    For early cancer initiation, several molecular modifications take place that assist cancer growth at initial stages. Among these alter-ations is DNA damage, the accumulation of DNA damage in com-bination with poor DNA repairing mechanisms that results in cancer cell formation. To explain why the levels of oxidative stress marker is low at later stages of BC compared with early stages of the cancer, one possible explanation is that at early stages of cancer, patients could be exposed to a high rate of endogenous and exogenous oxidative stress. The exogenous stress could be diminished at later stages of BC.