MedicalResearch.com Interview with:
Dr. Pam Marcus PhD
Epidemiology and Genomics Research Program
Division of Cancer Control and Population Sciences
National Cancer Institute
National Institutes of Health
Bethesda, MD 20892
MedicalResearch: Why do we need to consider targeted cancer screening?
Dr. Marcus: Cancer screening, the routine testing of asymptomatic individuals without a history of the disease of interest, is an important approach to cancer prevention and control. There is compelling evidence that screening for at least four cancers reduces disease-specific mortality, but population-based cancer screening also leads to unfavorable events. Only a minority of those screened will benefit, and many will have false-positive exams. Some screenees will experience undesirable sequelae, ranging from minor inconveniences to serious adverse events due to the exam itself or diagnostic evaluation.
MedicalResearch: What is the goal of targeted cancer screening in average-risk individuals?
Dr. Marcus: Targeted cancer screening attempts to segregate those who will benefit from screening from those who will not through use of information on disease risk. Average risk individuals are those not known to be at substantially elevated risk, including those without known inherited predisposition, without co-morbidities known to increase cancer risk, and without previous diagnosis of cancer or pre-cancer. The goal of targeted cancer screening in average risk individuals is to reduce the number of individuals who need to be screened while preserving the overarching benefit of reduced cancer-specific mortality in the general population. Targeted cancer screening is an example of precision medicine; visit http://www.nih.gov/precisionmedicine/goals.htm to learn more about the National Institute of Health’s Precision Initiative.
MedicalResearch: Do we already employ targeted cancer screening? Are there other factors on which we could target?
Dr. Marcus: Screening guidelines for average risk individuals currently target on age, smoking (lung cancer only), and in some instances race, family history of cancer, and previous negative screening history (cervical cancer only). Researchers have begun to explore the possibility of refining screening regimens for average risk individuals using combinations of genomic polymorphisms and additional non-genomic risk factors, including previous screening history.
MedicalResearch: Is there evidence to support targeted cancer screening in average risk individuals?
Dr. Marcus: Definitive evidence of a cancer screening benefit is accepted by most to be a reduction in disease-specific mortality, typically as observed in a. randomized controlled trial (RCT). Some RCTs suggest that targeting on certain ages and smoking histories reduces mortality for some cancers. Statistical modeling has been used to gauge possible benefits in populations and for scenarios not studied in RCTs. Observed elevated risk of cancer has led to screening recommendations based on race and family history, but no reduction in mortality has been convincingly demonstrated. Researchers are beginning to examine the relationship between genomic information and screening outcomes.
MedicalResearch: What does the future hold?
Dr. Marcus: In time, targeted cancer screening in average-risk individuals is likely to include genomic factors and past screening experience as well as non-genomic factors other than age, smoking, and race, but it is of utmost importance that clinical implementation be evidence-based.
Dr. Pam Marcus PhD (2015). Genomics Aims To Refine Cancer Screening Programs