Research Article: Prognostic Significance of Tumor Size of Small Lung Adenocarcinomas Evaluated with Mediastinal Window Settings on Computed Tomography

Date Published: November 3, 2014

Publisher: Public Library of Science

Author(s): Yukinori Sakao, Hiroaki Kuroda, Mingyon Mun, Hirofumi Uehara, Noriko Motoi, Yuichi Ishikawa, Ken Nakagawa, Sakae Okumura, Prasad S. Adusumilli.

http://doi.org/10.1371/journal.pone.0110305

Abstract

We aimed to clarify that the size of the lung adenocarcinoma evaluated using mediastinal window on computed tomography is an important and useful modality for predicting invasiveness, lymph node metastasis and prognosis in small adenocarcinoma.

We evaluated 176 patients with small lung adenocarcinomas (diameter, 1–3 cm) who underwent standard surgical resection. Tumours were examined using computed tomography with thin section conditions (1.25 mm thick on high-resolution computed tomography) with tumour dimensions evaluated under two settings: lung window and mediastinal window. We also determined the patient age, gender, preoperative nodal status, tumour size, tumour disappearance ratio, preoperative serum carcinoembryonic antigen levels and pathological status (lymphatic vessel, vascular vessel or pleural invasion). Recurrence-free survival was used for prognosis.

Lung window, mediastinal window, tumour disappearance ratio and preoperative nodal status were significant predictive factors for recurrence-free survival in univariate analyses. Areas under the receiver operator curves for recurrence were 0.76, 0.73 and 0.65 for mediastinal window, tumour disappearance ratio and lung window, respectively. Lung window, mediastinal window, tumour disappearance ratio, preoperative serum carcinoembryonic antigen levels and preoperative nodal status were significant predictive factors for lymph node metastasis in univariate analyses; areas under the receiver operator curves were 0.61, 0.76, 0.72 and 0.66, for lung window, mediastinal window, tumour disappearance ratio and preoperative serum carcinoembryonic antigen levels, respectively. Lung window, mediastinal window, tumour disappearance ratio, preoperative serum carcinoembryonic antigen levels and preoperative nodal status were significant factors for lymphatic vessel, vascular vessel or pleural invasion in univariate analyses; areas under the receiver operator curves were 0.60, 0.81, 0.81 and 0.65 for lung window, mediastinal window, tumour disappearance ratio and preoperative serum carcinoembryonic antigen levels, respectively.

According to the univariate analyses including a logistic regression and ROCs performed for variables with p-values of <0.05 on univariate analyses, our results suggest that measuring tumour size using mediastinal window on high-resolution computed tomography is a simple and useful preoperative prognosis modality in small adenocarcinoma.

Partial Text

We previously reported that the size of lung adenocarcinoma, evaluated using mediastinal window (MD) settings on computed tomography (CT), is a more important predictive prognosis factor than the total tumour size, evaluated using lung window (LD) settings [1] Various studies have documented the correlation between CT findings and the pathological features of lung adenocarcinoma [2]–[4]. The ground glass opacity (GGO) component is typically recognized as a bronchioloalveolar carcinoma (BAC) component on microscopic examination, and the BAC is now categorized as an adenocarcinoma in situ that does not affect tumour aggressiveness [5], [6]. In contrast, the solid component recognized as invasive lesion being so called scar, which excludes the BAC component in lepidic predominant adenocarcinoma, can be easily defined using MD settings on CT [1], [2], [5]. Moreover, the solid tumour recognized as a non-lepidic predominant adenocarcinoma, such as acinar, papillary, solid predominant or micropapillary predominant adenocarcinomas, is recognized as invasive adenocarcinoma and shows much more aggressiveness than that by lepidic predominant adenocarcinoma [2], [5], [7]. Therefore, we have emphasized the importance of determining the size of the solid tumour component in adenocarcinoma using MD settings when evaluating tumour aggressiveness [1], [2], [5].

This was a retrospective study conducted between October 2003 and December 2008 in patients with small lung adenocarcinomas (diameters of ≤3 cm) that underwent standard surgical resections (lobectomy with hilar and mediastinal lymph node dissection) at the Cancer Institute Hospital.

In total, 176 patients were enrolled. This subgroup that excluded BAC and small tumours (<1 cm) comprised 99 females and 77 males, with ages ranging from 34 to 78 (median  = 61) years. The follow-up periods ranged from 24–84 (median  = 49) months. Tumour diameter is a major prognostic factor for lung cancer. The most common method for determining tumour size before surgery is by CT using lung window settings [8]. Recently, attempts were made to classify small peripheral adenocarcinomas into subgroups according to the patterns of tumour growth, which are considered to be associated with the biological characteristics of tumours derived from clinicopathological examination[4], [6], [9]–[11]. These subgroups comprise the following: AIS (adenocarcinoma in situ), minimally invasive adenocarcinoma (3-cm lepidic predominant tumour with an invasion of ≤5 mm), lepidic predominant, acinar predominant, papillary predominant, micropapillary predominant, solid predominant with mucin production and invasive adenocarcinoma variants.   Source: http://doi.org/10.1371/journal.pone.0110305