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Comparative Study
. 2018 May;1(1):e180083.
doi: 10.1001/jamanetworkopen.2018.0083.

Concordance and Reproducibility of Melanoma Staging According to the 7th vs 8th Edition of the AJCC Cancer Staging Manual

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Free PMC article
Comparative Study

Concordance and Reproducibility of Melanoma Staging According to the 7th vs 8th Edition of the AJCC Cancer Staging Manual

Joann G Elmore et al. JAMA Netw Open. .
Free PMC article

Abstract

Importance: The recently updated American Joint Committee on Cancer (AJCC) classification of cancer staging, the AJCC Cancer Staging Manual, 8th edition (AJCC 8), includes revisions to definitions of T1a vs T1b or greater. The Melanoma Pathology Study database affords a comparison,of pathologists' concordance and reproducibility in the microstaging of melanoma according to both the existing 7th edition (AJCC 7) and the new AJCC 8.

Objective: To compare AJCC 7 and AJCC 8 to examine whether changes to the definitions of T1a and T1b or greater are associated with changes in concordance and reproducibility.

Design setting and participants: In this diagnostic study conducted as part of the national Melanoma Pathology Study across US states, 187 pathologists interpreting melanocytic skin lesions in practice completed 4342 independent case interpretations of 116 invasive melanoma cases. A consensus reference diagnosis and participating pathologists' interpretations were classified into the Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis class IV (T1a) or class V ( T1b) using both the AJCC 7 and AJCC 8 criteria.

Main outcomes and measures: Concordance with consensus reference diagnosis, interobserver reproducibility, and intraobserver reproducibility.

Results: For T1a diagnoses, participating pathologists' concordance with the consensus reference diagnosis increased from 44% (95% CI, 41%-48%) to 54% (95% CI, 51%-57%) using AJCC 7 and AJCC 8 criteria, respectively. The concordance for cases of T1b or greater increased from 72% (95% CI, 69%-75%) to 78% (95% CI, 75%-80%). Intraobserver reproducibility of diagnoses also improved, increasing from 59% (95% CI, 56%-63%) to 64% (95% CI, 62%-67%) for T1a invasive melanoma, and from 74% (95% CI, 71%-76%) to 77% (95% CI, 74%-79%) for T1b or greater invasive melanoma cases.

Conclusions and relevance: Melanoma staging in AJCC 8 shows greater reproducibility and higher concordance with a reference standard. Improved classification of invasive melanoma can be expected after implementation of AJCC 8, suggesting a positive impact on patients. However, despite improvement, concordance and reproducibility remain low.

Conflict of interest statement

Conflict of Interest Disclosures: Dr Elder reported serving as a consultant for Myriad Genetics and SciBase and receiving research funding from the National Institutes of Health/National Cancer Institute. Dr Barnhill reported a financial relationship with Myriad Genetics. Dr Longton reported receiving grants from Fred Hutchinson Cancer Research Center and the National Cancer Institute during the conduct of the study. Drs Titus, Weinstock, Pepe, and Piepkorn reported receiving grants from the National Cancer Institute during the conduct of the study. No other disclosures were reported.

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