Background & Objectives: There are many challenges in the execution of targeted
therapy in cancer due to tumor heterogeneity between individuals. In case of solid tumors this is
one of the reasons as to why genomic analysis from single tumor biopsy specimens underestimate
the mutational burdens in such heterogeneous tumors thus contributing to treatment failure and
drug resistance. Molecular characteristics redefine tumor classification for molecular targeted
therapies ensuring the best patient specific therapies with better specificity and cost effective ratio.
Functional imaging like Positron Emission Tomography & Computed Tomography (PET-CT)
with 18-F Fluorodeoxyglucose (FDG) has been extensively used in oncology to assess the glucose
metabolism in tumor cells since long. It has been further redefined to use other radiopharmaceutical
targets capable of tumor characterization, microenvironment, angiogenesis, proliferation, apoptosis,
receptor expression and few others. Among these the receptor expression in tumors have
been studied in detail and specific imaging probes have been developed for imaging with either
Single Photon Emission Computed Tomography (SPECT-CT) or PET-CT. Combination of these
diagnostic tool with the same vector has permitted an easy switch from diagnosis to therapy using
a therapeutic radionuclide when such expression is documented. Thus in Nuclear Medicine the
concept of Theranostics have been utilized with ease and successfully implemented the theranostic
concept and has become a valid example of personalized and precision medicine. Imaging and
therapy of thyroid cancer, neuroendocrine tumors and castration resistant prostate cancer are current
examples of this concept.
Conclusion: Molecular imaging has high potential to link target identification with therapy and
thus to personalize it. It also has a very high potential for in-vivo tissue characterization, to
improve prediction, prognostication, road map for biopsy and monitoring of therapy.
Keywords: Tumor heterogeneity, molecular characterization of tumor, functional imaging, SPECT-CT, PET-CT, FES,
68-Ga 177-Lu DOTA & PSMA.
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