Effect of computed tomography window settings and reconstruction plane on 8th edition T-stage classification in patients with lung adenocarcinoma manifesting as a subsolid nodule

doi:10.1016/j.ejrad.2017.11.015

European Journal of Radiology

Volume 98, January 2018, Pages 130-135

https://doi.org/10.1016/j.ejrad.2017.11.015 Get rights and content

Highlights

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Multiplanar measurement resulted in upstaging of cT-stage in up to 24.3% of SSNs.
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Clinical T-stages using mediastinal- and lung-window disagreed in nearly up to 50%.
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The agreement between clinical and pathological T-stage was moderate to good.

Abstract

Purpose

To assess the effect of window settings and reconstruction plane on clinical T-stage determined by solid portion size within subsolid nodules (SSNs), based on 8th-edition TNM standards.

Materials and methods

This retrospective study included 247 SSNs from 221 patients who underwent surgery for lung adenocarcinomas between Feb 2012 and Oct 2015. Two radiologists independently measured the diameter of the solid portion on axial, coronal, and sagittal planes using lung- and mediastinal-window. The largest diameter among the measurements on the three planes was referred to as multiplanar measurement. Inter-reader agreement as well as the correlation between the CT and pathologic measurements were calculated using intra-class correlation coefficients (ICCs). The proportions of disagreement in clinical T-stage on different measurement methods were measured. The κ values for agreement between clinical- and pathological T-stage were measured.

Results

Inter-reader agreement was moderate-to-excellent (ICC confidence interval [CI] range, 0.51–0.92) in lung-window, while it was good-to-excellent (0.77–0.95) in mediastinal-window. The correlation between the CT and pathologic measurements was good-to-excellent (ICC CI range, 0.63–0.82) in lung-window and fair-to-good (0.25–0.78) in mediastinal-window. The proportions of disagreement between clinical T-stages using mediastinal- and lung-window were 32.0%–41.7% and 33.6%–49.0% with axial and multiplanar measurement, respectively. Multiplanar measurement resulted in upstaging in 12.6%–15.8% and 19.0%–24.3% of cases with mediastinal- and lung-window, respectively, when compared with axial measurement alone. The κ values for agreement between clinical T-stage and pathological T-stage ranged from 0.53 to 0.69.

Conclusions

Mediastinal-window was a more stable method in the aspect of the inter-reader agreement, but the correlation between the CT and pathologic measurement was better in lung-window. The clinical T-stage varied in up to one-half of the cases according to the window setting, and multiplanar measurement resulted in upstaging in up to one-fourth of the cases.

Introduction

For patients with subsolid nodules (SSNs), accurate clinical staging is important for determining the extent of surgical resection preoperatively and predicting prognosis [1]. Clinical stage can be obtained in virtually all patients who undergo CT imaging, even before surgical resection [2]. Furthermore, due to the shrinkage after formalin fixation in resected specimen, CT measurement of the solid component may better represent the in-vivo state of the invasive component than pathologic measurement in some cases [3].

The 8th edition of the tumor, node, and metastasis (TNM) staging of lung cancers states that the clinical T-stage should be based on the size of its solid portion within SSNs [1]. In T₁ lung adenocarcinomas manifesting as SSNs, clinical T-stage is sub-categorized into the five categories as cT_is, cT_1mi, cT_1a, cT_1b, and cT_1c according to the diameter of solid portion. For clinical T-staging, the 8th edition TNM staging guideline suggests measuring the single largest dimension of the solid portion in lung or intermediate window settings [1]. However, it still leaves which window setting is the best method for measuring the solid component as research questions [1]. If the lesions are aligned along a craniocaudal axis, multiplanar reconstructions in the coronal and sagittal plane are recommended for obtaining a more accurate assessment of nodule size. However, measuring the solid portion in the three reconstruction planes increases reading times, when compared with that in the axial plane. To our knowledge, the difference between the clinical T-stage according to the reconstruction plane or window settings in patients with SSNs has never been investigated.

The present study aimed to assess the effect of window settings and reconstruction plane on clinical T-stage determined by solid portion size within SSNs, based on 8th edition TNM standards.

Section snippets

Materials and methods

This retrospective study was approved by the Institutional Review Board of Seoul National University Bundang Hospital (a tertiary referral center), which waived the requirement for informed consent.

Nodule characteristics

Nodules were confirmed by surgical procedures including 113 lobectomies, 106 sublobar resections, and six combinations of lobectomy and sublobar resection in different lobes. The mean time ± standard deviation between CT and surgery was 18.5 ± 13.1 days.

Pathologically, 24 of 247 SSNs were of stage T_is or less, 70 were of stage T_1mi, 55 were of stage T_1a, 82 were of stage T_1b, and 16 were of stage T_1c.

Intra- and inter-reader agreements

Intra-reader agreement was good-to-excellent (ICC CI range, 0.78–0.94) in lung-window and excellent

Discussion

The present study investigated the effect of various reconstruction planes and window settings on the determination of clinical T-stage based on 8th TNM standards in patients with lung adenocarcinoma. There was a considerable discrepancy between clinical T-stages using different measurement methods. The clinical T-stage varied in up to one-half of the cases according to the window setting, and multiplanar measurement resulted in upstaging in up to one-fourth of the cases.

Regarding the

Declaration of interest

The authors have no conflicts of interest.

Funding

This study was supported by a grant of the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI14C2175).

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Research articleEffect of computed tomography window settings and reconstruction plane on 8th edition T-stage classification in patients with lung adenocarcinoma manifesting as a subsolid nodule

Highlights

Abstract

Purpose

Materials and methods

Results

Conclusions

Introduction

Section snippets

Materials and methods

Nodule characteristics

Intra- and inter-reader agreements

Discussion

Declaration of interest

Funding

J. Thorac. Oncol.

J. Thorac. Oncol.

J. Thorac. Oncol.

The American Joint Committee on Cancer: the 7th edition of the AJCC cancer staging manual and the future of TNM

Ann. Surg. Oncol.

Recommendations for measuring pulmonary nodules at CT: a statement from the Fleischner Society

Radiology

Research article
Effect of computed tomography window settings and reconstruction plane on 8th edition T-stage classification in patients with lung adenocarcinoma manifesting as a subsolid nodule