Concordance, Reproducibility of Melanoma Staging: AJCC 8 Versus AJCC 7
Posted: Monday, July 2, 2018
With changes to reference diagnoses in the American Joint Committee on Cancer Staging Manual, 8th edition (AJCC 8), pathologists observing melanocytic skin lesions will agree about half the time—more than with AJCC 7—about the diagnosis of early-stage invasive melanoma. Accuracy in such diagnoses will thus likely remain relatively low, according to a study of the manual published in JAMA Network Open.
“For T1a diagnoses, participating pathologists’ concordance with the consensus reference diagnosis increased from 44% to 54% using AJCC 7 and AJCC 8 criteria, respectively,” wrote the team, led by Joann G. Elmore, MD, MPH, of the David Geffen School of Medicine, University of California, Los Angeles. AJCC 8 includes revisions to definitions of T1a versus T1b or greater. The 10% increase will positively impact patient treatment, agreed the researchers, but ideally, reference guidelines would mean that two qualified pathologists, tackling the same tissue, would give the same, correct diagnosis.
A total of 187 U.S. pathologists who interpret melanocytic skin lesions in practice participated in the study, completing 4,342 interpretations of 116 invasive melanoma cases. Each pathologist saw the same set of cases twice, unbeknownst to them, at least 8 months apart.
Concordance in diagnoses of invasive melanoma staged at T1b or greater was better: It increased from 72% with AJCC 7 to 78% with AJCC 8. As concordance did, intraobserver reproducibility of diagnoses improved, increasing from 59% to 64% for T1a and from 74% to 77% for T1b or greater.