At first glance, it is counterintuitive that imaging, the alleged instigator of overdiagnosis, can reduce overdiagnosis and overtreatment. Imaging can curb overdiagnosis if it juxtaposes between the gateway of overdiagnosis and biopsy or treatment or makes diagnosis prognostically meaningful. In this special issue, how imaging may affect overdiagnosis is discussed in relation to prostate cancer , Alzheimer disease , and psychiatric disorders .
Magnetic resonance imaging (MRI) and prostate cancer: overtesting to curb overtreatment
The gateway to the overdiagnosis of prostate cancer is the prostate-specific antigen (PSA) test. PSA is not at fault for its own sake but because the threshold for its positivity is so low and the population in which it is used is so broad that overdiagnosis is inevitable. Many believe that the strategies after a positive PSA are to blame for the overtreatment of prostate cancer . The scale of overdiagnosis is illustrated by a remarkable statistic—nearly 60% of 60-year-olds and 80% of 80-year-olds have prostate cancer at autopsy . Simply put, if we seek cancer in the prostate gland, we will likely find it.
Biopsy not only finds innocuous tumors but does not confidently exclude high-grade tumors. This is one reason why so often the whole gland is treated, by surgery or radiation, for a localized low-grade tumor. Biopsy therefore overdiagnoses, increases uncertainty, and leads to overtreatment.
For MRI to reduce overtreatment, it must gatekeep biopsy when PSA is positive or whole gland treatment when the biopsy is positive. Diffusion-weighted MRI detects high-grade tumors well but does not detect low-grade tumors as well. The differential sensitivity for consequential and innocuous tumors makes it plausible that MRI can reduce overdiagnosis, if biopsy is conditional on the positivity of MRI.
However, this paradigm has several challenges, which Rosenkrantz and Taneja discuss . The costs are notable even if only men with a positive PSA undergo MRI as well. Furthermore, because of indication drift, more people with a positive PSA could get an MRI than would have been sent for a biopsy. The negative predictive value of MRI for significant cancer is 90% . Will clinicians not biopsy the prostate if the MRI is negative?
MRI could mirror PSA so completely that everyone who gets a PSA gets an MRI as well. This is not difficult to imagine in our medical culture where prudence is neither rewarded nor respected. However, MRI could persuade clinicians to adopt surveillance instead of whole gland treatment. Overtreatment of prostate cancer will be curbed at the expense of overtesting.
PET and dementia: biomarker becomes the disease
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Neuroimaging and psychiatric disorders: the Gaussian trap
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Conclusions
Get Radiology Tree app to read full this article<
References
1. Rosenkrantz A.B., Taneja S.S.: Prostate MRI Can reduce overdiagnosis and overtreatment of prostate cancer. Acad Radiol 2015; 22: pp. 1000-1006.
2. Dubroff J., Nasrallah I.M.: Will PET amyloid imaging lead to overdiagnosis of Alzheimer’s disease?. Acad Radiol 2015; 22: pp. 988-994.
3. Nucifora P.: Overdiagnosis in the era of neuropsychiatric imaging. Acad Radiol 2015; 22: pp. 995-999.
4. Sakr W.A., Grignon D.J., Haas G.P., et. al.: Age and racial distribution of prostatic intraepithelial neoplasia. Eur Urol 1996; 30: pp. 138-144.
5. Insel T.R.: The NIMH Research Domain Criteria Project (RDoC) Project: precision medicine for psychiatry. Am. J. Psychiatry 2014; 171: pp. 395-397.
6. Szasz T.S.: The myth of mental illness.2010.Harper PerennialNew York Anv. Edition
7. Sheline Y.I., Wang P.W., Csernansky J.G., et. al.: Hippocampal atrophy in recurrent major depression. Proc Natl Acad Sci U S A 1996; 93: pp. 3908-3913.