Impact of computed tomography window settings on clinical T classifications and prognostic evaluation of patients with subsolid nodules

OBJECTIVES

To investigate the impact of lung window (LW) and mediastinal window (MW) settings on the clinical T classifications and prognostic prediction of patients with subsolid nodules.

METHODS

Seven hundred and nineteen surgically resected subsolid nodules were reviewed, grouping into pure ground-glass nodules (n = 179) or part-solid nodules (n = 540) using LW. Interobserver agreement on nodule classifications was assessed via kappa-value, and predictive performance of the solid portion measurement in LW and MW for pathological invasiveness and malignancy were compared using receiver-operating characteristic analysis. Cox regression was used to identify prognostic factors. Prognostic significance of T classifications based on LW (c[l]T) and MW (c[m]T) was evaluated by Kaplan-Meier method after propensity score matching. The performance of c(m)T for discrimination survival was estimated via the concordance index (C-index), net reclassification improvement and integrated-discrimination improvement.

RESULTS

By adopting MW, 124 part-solid nodules were reclassified as pure ground-glass nodules, and interobserver agreement improved to 0.917 (95% confidence interval 0.888-0.946). The solid portion size under MW more strongly predicted pathological invasiveness (P = 0.030), but did not better predict pathological malignancy. For remaining 416 part-solid nodules, c(l)T and c(m)T were both independent risk factors. c(m)T led to T classifications shifts in 321 nodules (14 upstaged and 307 downstaged) with no significant prognostic difference existing between the shifted c(m)T and matching c(l)T group after propensity score matching. The corrected C-index was improved to 0.695 (0.620-1.000) when adopting c(m)T with no significant difference in net reclassification improvement (P = 0.098) and integrated-discrimination improvement (P = 0.13) analysis.

CONCLUSIONS

As there is no significant benefit provided by MW in evaluating clinical T classification and prognosis, the current usage of LW is appropriate for assessing subsolid nodules.

Measurement Variability of Persistent Pulmonary Subsolid Nodules on Same-Day Repeat CT: What Is the Threshold to Determine True Nodule Growth during Follow-Up?

PURPOSE

To assess the measurement variability of subsolid nodules (SSNs) in follow-up situations and to compare the degree of variability between measurement metrics.

METHODS

Two same-day repeat-CT scans of 69 patients (24 men and 45 women) with 69 SSNs were randomly assigned as initial or follow-up scans and were read by the same (situation 1) or different readers (situation 2). SSN size and solid portion size were measured in both situations. Measurement variability was calculated and coefficients of variation were used for comparisons.

RESULTS

Measurement variability for the longest and average diameter of SSNs was ±1.3 mm (±13.0%) and ±1.3 mm (±14.4%) in situation 1, and ±2.2 mm (±21.0%) and ±2.1 mm (±21.3%) in situation 2, respectively. For solid portion, measurement variability on lung and mediastinal windows was ±1.2 mm (±27.1%) and ±0.8 mm (±24.0%) in situation 1, and ±3.7 mm (±61.0%) and ±1.5 mm (±47.3%) in situation 2, respectively. There were no significant differences in the degree of variability between the longest and average diameters and between the lung and mediastinal window settings (p>0.05). However, measurement variability significantly increased when the follow-up and initial CT readers were different (p<0.001).

CONCLUSIONS

A cutoff of ±2.2 mm can be reliably used to determine true nodule growth on follow-up CT. Solid portion measurements were not reliable in evaluating SSNs' change when readers of initial and follow-up CT were different.

Inter-reader variability when applying the 2013 Fleischner guidelines for potential solitary subsolid lung nodules

BACKGROUND

In 2013, the Fleischner Society published recommendations for managing subsolid pulmonary nodules. Inter-reader variability has not yet been defined and has potential implications for the ease and reproducibility of applying the guidelines to clinical practice.

PURPOSE

To evaluate inter-reader variability when applying the 2013 Fleischner guidelines for potential solitary subsolid lung nodules.

MATERIAL AND METHODS

Potential nodules were identified through a systematic retrospective review of CT studies that reported a ground-glass lesion. Three radiologists decided whether these lesions fit criteria of a subsolid nodule and thus merit application of the Fleischner Society guidelines, determined if a solid component was present, and measured each component in two dimensions. Final management recommendations were based on these intermediate decisions. Inter-reader variability for management was calculated and Fleiss' kappa was used to determine significance. Logistic regression and Fisher's exact test determined whether management was contingent on each intermediate decision.

RESULTS

Forty-four nodules with mean diameter of 9.4 mm were evaluated by three radiologists. Final management recommendations were in agreement for 93 out of 132 cases (70.4%, kappa = 0.56). Inter-reader variability in management recommendation was contingent on disagreement over whether a pulmonary lesion fit criteria of a subsolid nodule for 24 cases (P < 0.01), whether there was a solid component for 10 cases (P = 0.01), and whether the measurement met the threshold of 5 mm for five cases (P = 0.12).

CONCLUSION

There is moderate inter-reader variability when applying the 2013 Fleischner Society management recommendations. Significant contributors of variability include whether the potential lesions fit subsolid nodule criteria and whether a solid component is present. Measurement variability does not significantly affect the final management decisions.