**2. Diagnosis of breast cancer**

Breast cancer is currently the most common cancer in females and the second highest cause of cancer death in female population of the world. The majority of breast cancer deaths are due to metastasis (Costelloe et al., 2009). If breast cancer is detected prior to metastatic spread, it has considerably better prognosis than the cancer that has already spread. Therefore, the detection of cancer in an early stage is a major factor in the reduction of patient mortality and leading to less cancer costs and more successful treatments. The management of patients with a suspicious lesion includes confirming the diagnosis, identifying the stage of disease and choosing an appropriate treatment for each individual patient. Identifying the stage of a disease in any patient is a crucial step, because it determines the type of treatment that is appropriate for that particular person. Also, it is necessary to follow patients that need therapeutic procedures to assess their response to the treatment. There are a number of methods available for the detection of breast cancer. This section briefly points out some difficulties that encounter with these conventional imaging

Breast Cancer: Radioimmunoscintigraphy and Radioimmunotherapy 167

While breast cancer is still increasing in frequency, new diagnostic procedures must be available to challenge existing procedures to make diagnosis of breast cancer more accurate and reliable. DOT is one of the most important non-invasive and non-ionizing imaging modalities that are available for breast cancer diagnosis. DOT can be used to locate lesions within breast (Frangioni, 2008; Kepshire et al., 2007; Hawrysz et al, 2000). Despite promising results, there are several factors that limit the wide application of DOT for the imaging of breast tissue in clinic. First, the maximum depth of imaging in breast tissue is less than 15 mm. Secondly, the spatial resolution of DOT is less than one centimeter, that is not as good as mammography, ultrasonography or MRI. Because of these limitations, DOT is not a widely-accepted imaging modality for breast cancer (Kepshire et al., 2007; Hawrysz et al.,

X-ray computed tomography (introduced into clinical practice in 1972) was the first of modern slice-imaging modalities. CT scan has several advantages including (1) unlimited depth penetration; (2) high spatial resolution; (3) short acquisition time (minutes); (4) moderately cheap and (5) ability of performing anatomical imaging. CT has some limitations including (1) sensitivity of CT scan decreases in early stage of breast cancer, (2) CT scan is associated with radiation exposure and should never be done in pregnant females because of radiation risk to the fetus, (3) CT is not very good at identifying pathology of soft tissues, (4) the dye used in CT is iodine based and is often a cause of allergy and (5) CT probably can not be used for molecular imaging and currently is just used for anatomical

Several biochemical compounds in the serum/plasma may act as the indicators of the presence, risk or prognosis of cancer. In patients with history of breast cancer, elevated tumor marker levels may represent cases of tumor relapse. It has been shown that increasing levels of tumor markers is associated with disease recurrence and may indicate the need for further investigations. Examples of tumor markers in blood including CA 15.3, CA 27.29, CA125, CEA and circulating tumor cells. While breast cancer blood marker tests are promising, they are not absolutely conclusive. When a breast cancer blood marker test comes back negative, it doesn't necessarily mean that the patient is free and clear of breast cancer and a positive result does not always mean that the cancer is growing (Merkle et al.,

As cited, each imaging method has strengths and weaknesses in terms of sensitivity, specificity, spatial and temporal resolution, contrast and cost. Therefore, the fundamental efforts for introduction and development of new methods for breast cancer diagnosis are requested. Nuclear medicine is defined as a branch of medicine that employs open radioactive sources, commonly referred to radionuclides, in diagnosis and treatment of diseases (Glasspool & Evans, 2000). The application of nuclear medicine techniques to study patients with breast cancer has recently raised its profile particularly in the investigation of indeterminate mammographic lesions and for overcoming limitations of MRI, US, CT and

**2.4 Diffuse Optical Tomography (DOT)** 

**2.5 Computed Tomography (CT)** 

and functional imaging (Pysz et al., 2010).

**2.6 Measurement of tumor markers in blood** 

2000).

2009).

**2.7 Nuclear medicine** 

modalities and describes application of nuclear medicine techniques and targeted molecular imaging in the investigation of patients with breast cancer.
