to include all three variables: the tumor size and spread at detection, its growth rate,
and patient’s competing risks for mortality. Even a rapidly growing cancer may still
represent overdiagnosis if detected when it is very small or in a patient with limited
life expectancy.^31 Following the initiation of Japanese national screening program
for neuroblastoma, a rare neuroendocrine tumor in children, the number of children
diagnosed with this tumor extremely increased.^32 Therefore, a group of pediatric
oncologists decided to offer a “watchful waiting” strategy to the parents of children
with small lesions.^33 Cancer spontaneously regressed in all infants on this strategy,
which represents clear evidence of overdiagnosis. The magnitude of overdiagnosis
has been estimated to be as much as 25 % of mammographically detected breast
cancers, 50 % of chest X-ray and/or sputum-detected lung cancers, and 60 % of
prostate-specific antigen-detected prostate cancers.^34 Overdiagnosis should not be
confused with a false-positive result. A false-positive result in oncologic imaging
encompasses not only detection but frequently invasive diagnostics and therapy of
suspected lesions that finally appear nonmalignant. Our ability to detect smaller
lesions using novel technology simultaneously increases the necessity to charac-
terize such findings, resulting in the extension of diagnostics. A false-positive result
as a major concern of diagnostics is immediately discernible to the radiologist,
unlike overdiagnosis, which is evident a long time after the implementation of a
particular diagnostic method. Randomized clinical studies with undoubted proofs
of overdiagnosis have a strong influence on stakeholders when they make a decision
whether to finance the implementation/resumption of screening programs or not.
Modern radiology and nuclear medicine provide not only accurate morphologic
assessment of the tumor location, size, and extent but also physiological character-
istics of the lesion like perfusion, flow, diffusion, and metabolism. Perfusion-based
imaging is used to take advantage of neovascularity to discriminate benign struc-
tures from aggressive lesions and might help with the prediction of tumor behavior
and the assessment of the response to therapy.^35 By recording X-ray attenuation
during a passage of a contrast material through a region of interest, time-attenuation
curves are created by using a deconvolution algorithm, and perfusion parameters
can be generated such as blood flow, blood volume, mean transit time, and capillary
permeability. CT perfusion parameters not only allow evaluation of the hemody-
namic biologic status of a lesion but also have been helpful in predicting response to
chemo-irradiation.^36 There are several techniques for performing perfusion-
weighted MR imaging, of which the most widely available is T2*-weighted
(^31) Schoder et al. ( 2009 ).
(^32) Welch and Black ( 2010 ).
(^33) Bessho (1996a).
(^34) European Society of Radiology ( 2011 ) and Schoder et al. ( 2009 ).
(^35) Bessho (1996b).
(^36) Rumboldt et al. ( 2005 ).
The Role of Radiology in Personalized Medicine 225