Interobserver Variation in Vulvar Squamous Cell Cancer Depth of Invasion Using Two Measurement Methods.

Area of Science:

• Gynecologic Oncology
• Pathology
• Surgical Oncology

Background:

• Depth of invasion (DOI) is critical for predicting nodal metastasis risk in vulvar squamous cell carcinoma (vSCC).
• International guidelines for measuring DOI have diverged, with some adopting the FIGO 2021 "New" method and others retaining the FIGO 2009 "Old" method.
• This divergence necessitates evaluating the impact of each method on diagnostic consistency.

Purpose of the Study:

• To compare the interobserver variation in measuring depth of invasion for vSCC using the FIGO 2009 "Old" and FIGO 2021 "New" measurement strategies.
• To assess the clinical implications of differing DOI measurement methods on vSCC staging and management decisions.

Main Methods:

• Ten pathologists measured DOI on 50 vSCC images (0.1-3 mm DOI) using both Old and New FIGO methods.
• Statistical analyses included ANOVA, Student's t-test, and kappa statistics to evaluate interobserver agreement.
• Discrepancies in measurements, particularly those crossing the 1 mm threshold, were analyzed.

Main Results:

• The Old method resulted in a larger mean DOI (1.3 mm) compared to the New method (0.9 mm; p < .001).
• Higher interobserver variation was observed with the New method (68% disagreement spanning 1 mm) compared to the Old method (53% disagreement; κ = 0.6 vs 0.65).
• Interobserver variation was lower with the Old method when at least two pathologists measured DOI >1 mm (30/36 cases; mean difference = -0.1 mm).

Conclusions:

• The FIGO 2021 DOI measurement method demonstrates greater interobserver variability than the FIGO 2009 method, particularly for tumors with DOI >1 mm.
• The current lack of international consensus and limited clinical outcome data for the New method warrant a re-evaluation of the 2021 FIGO staging guidelines.
• Standardizing DOI measurement is crucial for accurate vSCC staging and patient management.