(ChemotherapyAdvisor) – The parametric empirical Bayes (PEB) longitudinal screening algorithm “identifies ovarian cancer earlier and at lower biomarker concentrations than a single-threshold (ST) screening algorithm adjusted to the same specificity,” a retrospective study concluded in the Journal of Clinical Oncology online December 17.
Cancer screening using blood-based biomarkers is convenient, inexpensive, and provides quantitative measurements of disease. Compared with ST rules, in which a positive result is noted when a biomarker concentration exceeds a common population-wide threshold, a longitudinal algorithm, such as the PEB, uses “information available from the screening history of an individual to personalize screening decisions,” Charles Drescher, MD, of the Fred Hutchinson Cancer Research Center, Seattle, WA, and colleagues noted. In addition, “compared with an ST rule, smaller deviations from baseline biomarker levels are required to identify a tumor.”
To determine how frequently and to what extent the PEB algorithm identifies ovarian cancer earlier than an ST rule, the investigators retrospectively evaluated serial preclinical serum CA125 values. These values were measured annually in 44 incident cases of ovarian cancer identified from participants in the Prostate Lung Colorectal and Ovarian Cancer (PLCO) Screening Trial.
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They found that “the PEB algorithm detected ovarian cancer earlier than an ST rule in a substantial proportion of cases.”
At 99% specificity, 20% of cases were identified earlier by using the PEB algorithm. This specificity corresponded to the ST-rule CA125 cutoff ≥35U/mL used in the PLCO trial.
“Among these cases, the PEB signaled abnormal CA125 values, on average, 10 months earlier and at a CA125 concentration 42% lower (20U/mL) than the ST-rule cutoff,” they wrote.
As the specificity of the screening rule was reduced, the proportion of cases detected earlier by the PEB algorithm and the earliness of detection both increased.
“The PEB algorithm warrants additional testing in randomized ovarian cancer–screening trials,” Dr. Drescher noted. “The algorithm is computationally simple, easy to implement, and readily adaptable to multiple and novel markers and screening programs that incorporate early recall.”
The PEB algorithm is currently being evaluated in a phase I screening trial, and it may prove useful for screening for other cancers for which biomarkers are available.
Link to abstract:
http://jco.ascopubs.org/content/early/2012/12/13/JCO.2012.43.6691.abstract
