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Role of Molecular Imaging in Personalized Therapy of Cancer
In oncology, if cancer cells are removed from their microenvironment, their pattern
of gene expression changes because the behavior of tumor cells is inextricably
linked to their environments. Therefore, noninvasive, quantitative means of detect-
ing gene and protein activity are essential. In vivo imaging is one method for
achieving this. Various technologies available for this purpose are PET scanning,
SPECT and MRI. Ultrasound and CT are being re-engineered to refl ect information
at the cellular level. In vivo optical imaging technologies have matured to the point
where they are indispensable laboratory tools for small animal imaging. Human
applications are being explored and the future for clinical optical imaging tech-
niques looks bright. Merging these molecular imaging techniques with minimally
or noninvasive image-guided therapeutic delivery techniques is an important goal
in the fi ght against cancer.
In investigational and clinical oncology there is a need for imaging technologies
that will indicate response to therapy prior to clinical evidence of response. The
conventional imaging methods such as CT and MRI enable anatomic measurements
of the tumor. This may be useful for assessing response to traditional cytotoxic
agents where tumor shrinkage occurs early. In contrast to this, molecularly targeted
agents tend to induce arrest of cancer cell growth and development, but not neces-
sarily signifi cant tumor shrinkage in the short term. Thus there is a need for func-
tional or molecular imaging methods that would give information about what is
happening in the tumor at the molecular level. One example of this approach is an
attempt to fi nd an explanation for poor performance of some antiangiogenesis drugs
in clinical trials despite abundant preclinical evidence that the drugs should work.
Noninvasive molecular imaging is needed to identify patients that are suitable for a
particular targeted therapy, and to determine if the drug is reaching its target and in
suffi cient quantities to block the target. The molecularly targeted approaches enable
the therapy to be individually tailored to a given patient’s tumor and metabolism.
CT may not be optimally suitable for assessment of oncolytic virus treatments
because of paradoxical infl ammatory tumor swellings, which result from virus
treatments, particularly when viruses are armed with immunostimulatory mole-
cules. In a comparative study of patients treated by viral oncolysis, FDG-PET was
more sensitive in detection of responses than tumor size determined by CT (Koski
et al. 2013 ).
Functional Diffusion MRI
Functional diffusion MRI scan could help physicians decide quickly whether treat-
ment for brain tumors is having any effect. The scan uses MRI to track the Brownian
motion of water through the brain (Moffat et al. 2005 ). Tumor cells block the fl ow
of water, so as those cells die, water diffusion patterns change, and the new MRI
technology can track it. Application of this technique in patients with malignant
10 Personalized Therapy of Cancer