By Onco’Zine Staff Wiriter
A nomogram that incorporates factors such as age, Gleason score, and prostate-specific antigen (PSA) level at diagnosis may be able to estimate if a screen-detected prostate cancer has beenoverdiagnosed according to a new study published January 6 in the Journal of the National Cancer Institute.
Researchers developed the over-diagnosis nomogram to assist both patients and clinicians make informed treatment decisions about screen-detected prostate cancers. Routine screening for prostate cancer has recently been viewed as a ?double-edged tool? in that it is associated with both potential benefits and potential harms. Specifically, the harms include unnecessary invasive diagnostics and treatment, as well as emotional distress due to detecting cancers that would never cause symptoms or become lethal.
…once an individual has been screened and found to have prostate cancer, the relevant question is the outcomes of various treatments …, and not the probability of an event that could have happened if the individual had not been screened…
Overdiagnosed cancers do not pose a risk to the patient and do not require treatment, but current interventions are associated with adverse effects that include impotence and incontinence. Studies have estimated that the risk of overdiagnosis for US males ranges from 23% to 42% of screen detections, although the risk of overdiagnosis can vary considerably, depending on factors such as the patient’s age and tumor characteristics. But these aspects highlight the need for a personalized tool that can better predict the likelihood of overdiagnosis, and thus reduce the risk of a patient receiving unnecessary treatment.
Led by Roman Gulati, M.S., from the Division of Public Health Sciences at the Fred Hutchinson Cancer Research Center in Seattle, WA, the researchers used a microsimulation model to generate life histories for a representative virtual population model of U.S. men aged 50 to 84 years from 1975 to 2005 and applied existing data on PSA levels, biopsy practices and cancer diagnosis patterns. The model used prostate cancer incidence data from the Surveillance, Epidemiology, and End Results registry to estimate risks of prostate cancer progression and detection in the absence and presence of PSA screening. It was designed for patients who presented with nonmetastatic disease and who were diagnosed via routine screening, with a PSA less than 10ng/mL.
A nomogram was then created to predict the individualized risk of overdiagnosis using patient age, Gleason score, and PSA at diagnosis. Screening and biopsy patterns were added on the model to determine when the men would have been diagnosed with and without screening, and who might have died from other causes. The prediction model that was eventually developed estimated that the chances of over-diagnosis range from 2.9% to 88.1%, depending on the patient?s individual factors.
The researchers write that ?It is hoped that the resulting nomogram, tailored to individual patient characteristics known at diagnosis, will provide useful information for patients and their physicians seeking to weigh the likely harms and benefits of the treatment options available for contemporary screen-detected prostate cancers.”
In an accompanying editorial, Boris Freidlin, Ph.D. and Edward L. Korn, Ph.D., from the Biometric Research Branch, Division of Cancer Treatment and Diagnosis at the National Cancer Institute in Bethesda, MD, do caution that every step of the modeling process described in this study “multiple unverifiable assumptions that can produce bias.” While they note that microsimulation could still be useful to increase generalizability of results from randomized trial results, the editorialists question if this model can be useful in guiding treatment decisions of patients with screen-detected prostate cancer:
“?once an individual has been screened and found to have prostate cancer, the relevant question is the outcomes of various treatments (treatment morbidity, prostate cancer symptoms and death), and not the probability of an event [detection of prostate cancer] that could have happened if the individual had not been screened,” they note.
For more information:
 Gulati R, Inoue LYT, Gore JL, Katcher J, Etzioni R. Individualized Estimates of Overdiagnosis in Screen-Detected Prostate Cancer JNCI J Natl Cancer Inst (2014)doi: 10.1093/jnci/djt367(First published online: January 7, 2014) [Article]
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