**4.1 Targeted molecular imaging**

Recent advances in molecular and cellular biology have facilitated the discovery of novel molecular targets on tumor cells such as key molecules involved in proliferation, differentiation, cell death and apoptosis, angiogenesis, invasion and metastasis or associated with cancer cell stemness (William et al., 2008). Molecular imaging is defined as visualization, characterization and measurement of biological processes at the molecular and cellular levels in human beings and other living systems (Pysz et al., 2010). Today, molecular imaging is increasingly used in clinical oncology, because molecular imaging is a non-invasive diagnostic method that allows for more sensitive and specific monitoring of key cancer-related molecular targets in vivo and is expected to play an important role in future cancer diagnosis. Generally, molecular targets can be applied to (Meel et al., 2010; Neves & Brindle, 2006):


5. Staging the extent of disease

170 12 Chapters on Nuclear Medicine

their growth. Currently, there are at least three FDA-approved antibodies for targeting of

• Trastuzumab (Herceptin) that is bound to the extracellular domain of Her2/neu

• Bevacizumab that is bound to vascular endothelial growth factor receptors (VEGFRs). Immunotherapy of breast cancer may cause side effects such as fever, chill, pain, weakness, nausea, vomiting, diarrhea, headache, and rash. These side effects generally become less severe after the first treatment. In addition, immunotherapy is a very expensive method for

The researchers are trying to improve the methods that can decrease the dose of drugs and transfer them just to the tumor cells with high efficiency and kill the cancer cells without affecting healthy cells. The recent improvements in biology of tumor cells, have introduced new methods in diagnosis and therapy of cancer named targeted molecular imaging and therapy (Sawyers, 2004). The knowledge of the diversities between tumor and normal tissues is the key to identify novel targets for new selective diagnosis and therapeutic strategies (Gasparini et al., 2005). The aim of these methods is to deliver a drug for therapy or a contrast agent for imaging just to the tumor site or cancer cells using different technologies. In these methods, not only the dose of drugs is decreased, but also the damage to the normal tissues is decreased. On the other hand, the probability of the diagnosis and therapy is increased too. In addition, the targeting methods in comparison with other methods have fewer side effects and the patients tolerate less physical and mental hurts. Tumor markers are used for targeting cancer cells in molecular imaging and therapy methods. Tumor marker is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacologic responses to a therapeutic

Recent advances in molecular and cellular biology have facilitated the discovery of novel molecular targets on tumor cells such as key molecules involved in proliferation, differentiation, cell death and apoptosis, angiogenesis, invasion and metastasis or associated with cancer cell stemness (William et al., 2008). Molecular imaging is defined as visualization, characterization and measurement of biological processes at the molecular and cellular levels in human beings and other living systems (Pysz et al., 2010). Today, molecular imaging is increasingly used in clinical oncology, because molecular imaging is a non-invasive diagnostic method that allows for more sensitive and specific monitoring of key cancer-related molecular targets in vivo and is expected to play an important role in future cancer diagnosis. Generally, molecular targets can be applied to (Meel et al., 2010;

1. Detection: screening high-risk groups and large populations of asymptomatic

2. Diagnosis of cancer in individuals with signs or symptoms

breast cancers (Stipsanelli & Valsamaki, 2005; Disis et al., 1994a, 1997b):

• Pertuzumab that is bound to a different epitope of Her2/neu receptor

**4. Targeted molecular imaging and therapy**

intervention (Meel et al., 2010).

Neves & Brindle, 2006):

3. As a prognostic indicator

4. Localization of tumor and metastases

individuals

**4.1 Targeted molecular imaging** 

receptor

patients.


A molecular imaging agent typically consists of a signaling moiety (radionuclide in nuclear medicine) and a functional target. Specific targeting of cancer-associated targets with radiolabeled targeting agents (e.g. antibodies, peptides and non-immunoglobulin proteins) and the use of subsequent visualization systems like gamma camera, SPECT and PET are examples of molecular imaging methods in nuclear medicine.
