A nomogram for preoperative prediction of invasiveness in solitary pulmonary adenocarcinoma: a multicenter study
Original Article

A nomogram for preoperative prediction of invasiveness in solitary pulmonary adenocarcinoma: a multicenter study

Xiaocui Liu1,2,3#, Dan Wang4#, Xiuying Yang5, Xiaofei Yue6, Chuansheng Zheng1,2,3, Liming Xia7, Xuefeng Kan1,2,3

1Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; 2Hubei Provincial Clinical Research Center for Precision Radiology & Interventional Medicine, Wuhan, China; 3Hubei Province Key Laboratory of Molecular Imaging, Wuhan, China; 4Department of Radiology, Taikang Tongji (Wuhan) Hospital, Wuhan, China5Department of Radiology, Jinshan Hospital, Fudan University, Shanghai, China; 6Department of Radiology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China; 7Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

Contributions: (I) Conception and design: C Zheng, L Xia, X Kan; (II) Administrative support: L Xia, X Kan; (III) Provision of study materials or patients: X Liu, X Yang, X Yue, C Zheng, L Xia; (IV) Collection and assembly of data: X Liu, D Wang, X Yang, X Yue; (V) Data analysis and interpretation: X Liu, D Wang; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

#These authors contributed equally to this work.

Correspondence to: Xuefeng Kan, MD, PhD. Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan 430022, China; Hubei Provincial Clinical Research Center for Precision Radiology & Interventional Medicine, Wuhan, China; Hubei Province Key Laboratory of Molecular Imaging, Wuhan, China. Email: xkliulang1314@163.com; Liming Xia, MD, PhD. Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan 430030, China. Email: lmxia@tjh.tjmu.edu.cn.

Background: The invasive pulmonary adenocarcinoma and preinvasive-minimally invasive lesions usually need different surgical operation methods. This study aims to develop a clinical prediction model for preoperatively assessing invasiveness in solitary pulmonary adenocarcinoma.

Methods: From January 2020 to December 2024, patients with solitary pulmonary nodules who underwent preoperative computed tomography (CT) scans in four centers were included. The patients were divided into a training dataset and an external testing dataset. Based on postoperative histopathology, patients were categorized into group A (atypical adenomatous hyperplasia, adenocarcinoma in situ, and minimally invasive adenocarcinoma) and group B (invasive adenocarcinoma). Logistic regression analyses were performed to establish a clinical prediction model and of which its performance was validated. Receiver operating characteristic curve was used to quantify discriminative ability, and a nomogram was generated to visualize the individualized risk probability.

Results: Four hundred and forty-eight patients were included, with 335 patients in the training dataset (Group A: 156; Group B: 179) and 113 patients in the external testing dataset (Group A: 53; Group B: 60). Four independent predictors were identified in the training dataset: cytokeratin 19 fragment (CYFRA 21-1) [odds ratio (OR): 4.175; 95% confidence interval (CI): 1.253–13.904; P=0.02], maximum diameter (OR: 1.247; 95% CI: 1.143–1.361; P<0.001), density type (OR: 6.604; 95% CI: 3.519–12.393; P<0.001), and air bronchogram (OR: 3.149; 95% CI: 1.406–7.051; P=0.005). The nomogram model demonstrated a robust diagnostic performance with area under the curves (AUCs) of 0.925 (95% CI: 0.897–0.953) in the training cohort and 0.895 (95% CI: 0.829–0.961) in the testing cohort.

Conclusions: The integration of tumor markers with CT imaging features enables preoperative noninvasive prediction of invasiveness in pulmonary adenocarcinoma.

Keywords: Tumor markers; computed tomography (CT); solitary pulmonary nodule (SPN); pulmonary adenocarcinoma; invasiveness assessment


Submitted May 11, 2025. Accepted for publication Jul 25, 2025. Published online Oct 22, 2025.

doi: 10.21037/jtd-2025-950


Highlight box

Key findings

• The integration of serum tumor markers with computed tomography (CT) features enables preoperative discrimination between invasive and preinvasive-minimally invasive lesions.

What is known and what is new?

• The association of CT radiological features and the invasiveness of lung adenocarcinoma is known.

• We established novel findings about the association of tumor markers with the invasiveness of lung adenocarcinoma.

What is the implication, and what should change now?

• This study holds potential for clinical translation, providing a basis for precise individualized treatments.


Introduction

Lung cancer remains the leading cause of cancer-related mortality worldwide (1). Approximately 80% to 85% of lung cancers are non-small cell lung cancer, of which its histological subtypes include adenocarcinoma, squamous cell carcinoma, large cell carcinoma, and others. Among these, adenocarcinoma represents the most prevalent histopathological type, accounting for approximately 40% of all lung cancers (2,3). Pulmonary adenocarcinoma-related lesions encompass precursor glandular lesions and adenocarcinoma. The former includes atypical adenomatous hyperplasia (AAH) and adenocarcinoma in situ (AIS), while the latter comprises minimally invasive adenocarcinoma (MIA) and invasive adenocarcinoma (IAC) (4). In the multi-step progression model of adenocarcinoma, the disease progresses sequentially from AAH, AIS, MIA to IAC (4,5). AAH, AIS, and MIA always present with indolent growth patterns and a favorable prognosis, with 5-year survival rates approaching 100%, whereas IAC is associated with a significantly poorer prognosis (40–80%) (6,7).

A solitary pulmonary nodule (SPN) is defined as an isolated nodular lesion ≤3 cm in diameter within the lung parenchyma, surrounded by aerated lung tissue, with a round/oval or irregular appearance on computed tomography (CT) imaging (8). With the widespread use of low-dose CT and high-resolution CT in lung nodule screening and follow-up, along with the assistance of artificial intelligence technology, the detection rate of lung adenocarcinoma that presents with lung nodules has been significantly increased, leading to a reduction of lung cancer-related mortality (9-12). Lung adenocarcinoma appearing as SPNs usually corresponds to clinical stage IA and its treatment options mainly include wedge resection, segmentectomy, and lobectomy (13,14). For early-stage non-invasive adenocarcinomas, sublobar resection achieves a comparable recurrence-free survival rate to lobectomy (15,16). AAH requires periodic surveillance, AIS and MIA necessitate either close follow-up or limited resection (segmentectomy/wedge resection), whereas IAC often needs a standard lobectomy (17). Compared to IAC, AAH/AIS/MIA, which exhibit overlapping imaging features, represent low-risk entities, and require a relatively conservative management. Therefore, a precise differential diagnosis is needed to facilitate individualized treatments and improve the clinical outcomes of these patients.

Tumor biomarkers, that are the biochemical indicators and reflect biological processes, can be utilized for the early diagnosis of diseases (18,19). Tumor biomarker screening offers distinct advantages including minimal invasiveness, high reproducibility, convenient sampling, and technical simplicity. The elevation of serum tumor markers may precede clinical symptom onset, which thereby enables a noninvasive early detection of tumor. Furthermore, longitudinal tumor marker variations facilitate histopathological subtyping, staging, and tumor burden quantification, thereby informing personalized treatment strategies (20). This study innovatively stratifies SPN patients into invasive (IAC) and preinvasive-minimally invasive (AAH/AIS/MIA) groups based on pathological diagnosis. A clinical predictive model, which innovatively integrated serum tumor markers with CT imaging features, was developed to noninvasively predict the invasiveness in solitary pulmonary adenocarcinoma before surgery, with the aim to assist in selecting segmentectomy or lobectomy treatments. We present this article in accordance with the TRIPOD reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-950/rc).


Methods

Patient population

From January 2020 to December 2024, patients with pulmonary adenocarcinoma that appear as SPNs in CT scans were recruited from four centers, including Wuhan Union Hospital (center I), Wuhan Tongji Hospital (center II), Shanghai Jinshan Hospital (center III), and the First Affiliated Hospital of Zhengzhou University (center IV) of China. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the institutional ethics committees of Union Hospital (No. 2025-0140), Tongji Hospital (No. TJ-IRB202401064), Jinshan Hospital (No. 2024-S48), and The First Affiliated Hospital of Zhengzhou University (No. 2024-KY-0862-001). Informed consent was waived due to the retrospective nature of the study.

The inclusion criteria of this study were as follows: (I) pathologically confirmed AAH, AIS, MIA, or IAC through surgical resection; (II) availability of preoperative non-contrast chest CT scans within one month before surgery; (III) presence of SPN on CT imaging with maximum diameter ranging from 5 to 30 mm; (IV) complete clinical documentation. The exclusion criteria were as follows: (I) suboptimal chest CT image quality, such as motion artifacts or noise; (II) incomplete clinical documentation; (III) lesion diameter less than 5 mm on CT imaging; (IV) nodules radiographically indistinguishable from pleural lesions; (V) multiple pulmonary nodules.

Equipment and parameters

The following CT scanners were utilized across participating institutions, as shown in Table S1. All scans utilized a head-first supine position. Patients were instructed to hold their breath after deep inspiration. The scan range extended from the lung apex to the subdiaphragmatic region. Non-contrast CT parameters are summarized in Table S2. Raw data were reconstructed with lung or standard kernels at 1.0–1.5 mm slice thickness and 20–30% overlap.

Collection of clinical data and analysis of imaging findings

The clinical data of patients were collected, including gender, age, smoking history, tumor history (history of malignant tumors), serum tumor markers, and pathological diagnosis. The tumor markers included carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), squamous cell carcinoma antigen (SCC), and cytokeratin 19 fragment (CYFRA 21-1). CT images were reviewed using Radiant Digital Imaging and Communications in Medicine (DICOM) Viewer (version 2021.2.2; Medixant). Qualitative data included lobe distribution (right upper lobe, right middle lobe, right lower lobe, left upper lobe, left lower lobe), density type (ground-glass, part-solid, and solid nodule), shape (round/oval, irregular), margin (clear, unclear), spiculation, pleural retraction sign, lobulation sign, air bronchogram, and cavitation. These qualitative imaging features were independently assessed by two radiologists with more than five years of experience in a double-blind way. Cases with significant discrepancies were resolved through discussion. The maximum diameter of the nodule (mm) was measured independently by the two radiologists, and the average value was calculated. CT scans for all patients were independently reviewed in a blinded fashion by two senior radiologists from the Department of Radiology at a tertiary hospital. Discrepancies were adjudicated by a chief diagnostic radiologist (CDR).

Statistical analysis

Statistical analysis was performed by SPSS software (version 26.0.0.0; IBM). Inter- and intrareader agreement was assessed using Cohen’s κ for qualitative variables and the intraclass correlation coefficient (ICC) for quantitative variables. Comparisons of categorical variables were conducted with the Chi-squared test, Yates’ continuity correction, or Fisher’s exact test. For quantitative variables, normality was first evaluated using the Shapiro-Wilk test, and homogeneity of variance was assessed via Levene’s test. Variables conforming to a normal distribution were analyzed using the t-test, while non-normally distributed variables were analyzed using the nonparametric Mann-Whitney U test. A P<0.05 indicated statistical significance. All parameters were analyzed by univariate and multivariate binary logistic regression to identify the independent risk factors and establish a clinical prediction model. In the univariate analysis, variables with P values <0.05 were initially selected for inclusion in the subsequent multivariate analysis. The multivariate analysis was then performed using the Enter method. The predictive performance was evaluated with the receiver operating characteristic (ROC) curve. The calibration curves were employed to assess goodness-of-fit, decision curve analysis (DCA) was used to evaluate the clinical utility, and a nomogram was constructed to visualize the scoring system. Additionally, ROC curve analysis was conducted to compute the model’s accuracy, specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) with its 95% confidence interval (CI). The Hosmer-Lemeshow test was applied to assess the model’s goodness-of-fit. Statistical visualizations were generated in Python (version 3.12.4) utilizing the following libraries: scikit-learn, dcurves, and statsmodels. Graphical outputs were uniformly formatted with Matplotlib to ensure the clarity and consistency.


Results

Patient recruitment

The patient enrollment flowchart is shown in Figure 1. A total of 776 patients were initially screened: 563 at the main center I, 213 at the branch centers II, III and IV. Of these, 335 patients from the former were allocated to the training cohort (4 AAH, 60 AIS, 92 MIA, 179 IAC), while 113 patients from the latter were assigned to the external testing cohort (2 AAH, 21 AIS, 30 MIA, 60 IAC). The pre-invasive/micro-invasive group (MIA, AIS, and AAH) and the invasive group (IAC) were designated as Group A and Group B, respectively. Finally, 448 patients were included: 335 cases in the training cohort (male: 110, female: 225; age, 49–64 years; Group A: 156, Group B: 179) and 113 cases in the testing cohort (male: 35, female: 78; age: 49–64 years; Group A: 53, Group B: 60).

Figure 1 Inclusion and exclusion flowchart for the training and testing cohorts. AAH, atypical adenomatous hyperplasia; AIS, adenocarcinoma in situ; CT, computed tomography; IAC, invasive adenocarcinoma; MIA, minimally invasive adenocarcinoma.

Clinical data

As shown in Table 1, statistically significant differences (P<0.05) were observed in age and tumor markers (CEA, CYFRA 21-1) between Group A and Group B in both the training and testing datasets, while no significant differences were found in the other variables. There were no statistically significant differences (P>0.05) between the training and testing cohorts regarding the clinical data of age, gender, smoking history, tumor history, CEA, NSE, SCC, and CYFRA 21-1, indicating the consistence of different cohorts.

Table 1

Baseline characteristics of patients in the two datasets

Characteristic Training dataset Testing dataset P
Total (n=335) Group A (n=156) Group B (n=179) P Total (n=113) Group A (n=53) Group B (n=60) P
Age (years) 56 [49–64] 53 [41–59] 59 [54–66] <0.001* 58 [49–64] 54 [41–62] 60 [54–64] 0.03* 0.76
Gender 0.07 0.44 0.80
   Female 225 (67.16) 113 (72.44) 112 (62.57) 78 (69.03) 39 (73.58) 39 (65.00)
   Male 110 (32.84) 43 (27.56) 67 (37.43) 35 (30.97) 14 (26.42) 21 (35.00)
Smoking history 0.32 0.97 0.08
   No 313 (93.43) 143 (91.67) 170 (94.97) 99 (87.61) 47 (88.68) 52 (86.67)
   Yes 22 (6.57) 13 (8.33) 9 (5.03) 14 (12.39) 6 (11.32) 8 (13.33)
Tumor history 0.26 0.34 0.89
   No 311 (92.84) 148 (94.87) 163 (91.06) 106 (93.81) 48 (90.57) 58 (96.67)
   Yes 24 (7.16) 8 (5.13) 16 (8.94) 7 (6.19) 5 (9.43) 2 (3.33)
CEA (μg/L) <0.001* 0.02* 0.72
   <5.0 308 (91.94) 153 (98.08) 155 (86.59) 102 (90.27) 52 (98.11) 50 (83.33)
   ≥5.0 27 (8.06) 3 (1.92) 24 (13.41) 11 (9.73) 1 (1.89) 10 (16.67)
NSE (μg/L) 0.51 0.85 0.98
   <16.3 309 (92.24) 146 (93.59) 163 (91.06) 105 (92.92) 50 (94.34) 55 (91.67)
   ≥16.3 26 (7.76) 10 (6.41) 16 (8.94) 8 (7.08) 3 (5.66) 5 (8.33)
SCC (ng/mL) >0.99 >0.99 0.98
   <1.5 312 (93.13) 145 (92.95) 167 (93.30) 106 (93.81) 50 (94.34) 56 (93.33)
   ≥1.5 23 (6.87) 11 (7.05) 12 (6.70) 7 (6.19) 3 (5.66) 4 (6.67)
CYFRA21-1 (ng/mL) 0.02* 0.012* 0.64
   <2.5 298 (88.96) 146 (93.59) 152 (84.92) 98 (86.73) 51 (96.23) 47 (78.33)
   ≥2.5 37 (11.04) 10 (6.41) 27 (15.08) 15 (13.27) 2 (3.77) 13 (21.67)

Data are presented as n (%) or median [interquartile range]. Group A: atypical adenomatous hyperplasia, adenocarcinoma in situ, and minimally invasive adenocarcinoma; Group B: invasive adenocarcinoma. *, P<0.05. CEA, carcinoembryonic antigen; CYFRA 21-1, cytokeratin 19 fragment; NSE, neuron-specific enolase; SCC, squamous cell carcinoma antigen.

CT radiological features

Figure 2 displays the pathological results corresponding to different SPN lesions, and Figure 3 provides examples of qualitative features in CT images. Inter- and intrareader agreement analyses for all CT imaging features demonstrated excellent consistency (all Cohen’s κ and ICC >0.8). As shown in Table 2, statistically significant differences (P<0.01) were observed between Group A and Group B in the training and testing datasets for pulmonary nodule imaging characteristics, including maximum diameter, density type, shape, spiculation, pleural retraction, lobulation, and air bronchogram, while there were no significant differences in other features. Except for density type, no statistically significant differences (P>0.05) were found in imaging characteristics between the training cohort and external testing cohort.

Figure 2 Pathological findings corresponding to different solitary pulmonary nodules. CT images and pathological findings of a patient with atypical adenomatous hyperplasia (A-C), adenocarcinoma in situ (D-F), minimally invasive adenocarcinoma (G-I), and invasive adenocarcinoma (J-L). The red arrows (A,D,G,J) point to the pulmonary nodules. All pathology images are shown at ×40 (B,E,H,K) and ×100 (C,F,I,L) original magnification by H&E staining. CT, computed tomography; H&E, hematoxylin and eosin.
Figure 3 CT characteristics of solitary pulmonary adenocarcinoma. As indicated by the red arrow: (A) irregular shape; (B) oval shape; (C) unclear margin; (D) clear margin; (E) spiculation; (F) lobulation sign; (G) pleural retraction sign; (H) cavitation; (I) air bronchogram; (J) pure ground-glass nodule; (K) ground-glass component (blue arrow) and solid component (red arrow) of a part-solid nodule; (L) solid nodule. All CT images are displayed in the lung window (window level/window width, −600/1,400). CT, computed tomography.

Table 2

CT radiological features of patients in the two datasets

Features Training dataset Testing dataset P
Total (n=335) Group A (n=156) Group B (n=179) P Total (n=113) Group A (n=53) Group B (n=60) P
Lobe location 0.35 0.43 0.16
   Left upper lobe 103 (30.75) 50 (32.05) 53 (29.61) 24 (21.24) 13 (24.53) 11 (18.33)
   Left lower lobe 47 (14.03) 17 (10.90) 30 (16.76) 19 (16.81) 7 (13.21) 12 (20.00)
   Right upper lobe 104 (31.04) 54 (34.62) 50 (27.93) 45 (39.82) 18 (33.96) 27 (45.00)
   Right middle lobe 26 (7.76) 13 (8.33) 13 (7.26) 5 (4.42) 3 (5.66) 2 (3.33)
   Right lower lobe 55 (16.42) 22 (14.10) 33 (18.44) 20 (17.70) 12 (22.64) 8 (13.33)
Maximum diameter, mm 13.80±5.69 10.28±4.21 16.87±5.00 <0.001* 13.43±4.96 10.66±3.89 15.89±4.51 <0.001* 0.79
Density type <0.001* <0.001* 0.03*
   Ground-glass nodule 106 (31.64) 88 (56.41) 18 (10.06) 40 (35.40) 33 (62.26) 7 (11.67)
   Part-solid nodule 159 (47.46) 65 (41.67) 94 (52.51) 62 (54.87) 19 (35.85) 43 (71.67)
   Solid nodule 70 (20.90) 3 (1.92) 67 (37.43) 11 (9.73) 1 (1.89) 10 (16.67)
Shape <0.001* <0.001* 0.22
   Round/oval 121 (36.12) 75 (48.08) 46 (25.70) 33 (29.20) 24 (45.28) 9 (15.00)
   Irregular 214 (63.88) 81 (51.92) 133 (74.30) 80 (70.80) 29 (54.72) 51 (85.00)
Border 0.76 0.61 0.26
   Clear 200 (59.70) 95 (60.90) 105 (58.66) 60 (53.10) 30 (56.60) 30 (50.00)
   Unclear 135 (40.30) 61 (39.10) 74 (41.34) 53 (46.90) 23 (43.40) 30 (50.00)
Spiculation <0.001* <0.001* 0.057
   No 224 (66.87) 139 (89.10) 85 (47.49) 87 (76.99) 50 (94.34) 37 (61.67)
   Yes 111 (33.13) 17 (10.90) 94 (52.51) 26 (23.01) 3 (5.66) 23 (38.33)
Pleural retraction <0.001* <0.001* 0.30
   No 196 (58.51) 128 (82.05) 68 (37.99) 73 (64.60) 47 (88.68) 26 (43.33)
   Yes 139 (41.49) 28 (17.95) 111 (62.01) 40 (35.40) 6 (11.32) 34 (56.67)
Lobulation <0.001* <0.001* 0.84
   No 222 (66.27) 130 (83.33) 92 (51.40) 73 (64.60) 48 (90.57) 25 (41.67)
   Yes 113 (33.73) 26 (16.67) 87 (48.60) 40 (35.40) 5 (9.43) 35 (58.33)
Air bronchogram <0.001* <0.001* 0.13
   No 241 (71.94) 141 (90.38) 100 (55.87) 72 (63.72) 48 (90.57) 24 (40.00)
   Yes 94 (28.06) 15 (9.62) 79 (44.13) 41 (36.28) 5 (9.43) 36 (60.00)
Cavitation 0.10 >0.99 0.89
   No 308 (91.94) 148 (94.87) 160 (89.39) 105 (92.92) 49 (92.45) 56 (93.33)
   Yes 27 (8.06) 8 (5.13) 19 (10.61) 8 (7.08) 4 (7.55) 4 (6.67)

Data are presented as n (%) or mean ± standard deviation. Group A: atypical adenomatous hyperplasia, adenocarcinoma in situ, and minimally invasive adenocarcinoma; Group B: invasive adenocarcinoma. *, P<0.05. CT, computed tomography.

Logistic regression model

The univariate and multivariate analysis results for the training cohort are shown in Table 3. Univariate analysis revealed significant associations between age, tumor markers (CEA, CYFRA 21-1), and CT imaging features (maximum diameter, density type, shape, spiculation, pleural retraction, lobulation, and air bronchogram) and invasiveness (P<0.05 for all). Subsequent multivariate logistic regression analysis further identified four independent risk factors for differentiating Group A and Group B: CYFRA 21-1 [odds ratio (OR): 4.175; 95% CI:1.253–13.904; P=0.02], maximum diameter (OR; 1.247; 95% CI: 1.143–1.361; P<0.001), density type (OR: 6.604; 95% CI: 3.519–12.393; P<0.001), and air bronchogram (OR: 3.149;95% CI: 1.406–7.051; P=0.005). A logistic regression clinical prediction model was constructed using the training dataset and validated with the testing dataset. Figure 4 presents the nomogram for the training cohort. ROC curve analysis (Table 4, Figure 5A) demonstrated a robust and comparable diagnostic performance in the two datasets. The training dataset achieved an AUC of 0.925 (95% CI: 0.897–0.953), accuracy of 0.863, sensitivity of 0.872, specificity of 0.853, PPV of 0.872, NPV of 0.853 (P<0.001), while the external testing dataset yielded an AUC of 0.895 (95% CI: 0.829–0.961), accuracy of 0.876, sensitivity of 0.833, specificity of 0.925, PPV of 0.926, NPV of 0.831 (P<0.001). The calibration curve (Figure 5B) and Hosmer-Lemeshow test indicated a good model fit, with no significant deviation from the ideal calibration line (training dataset: χ2=10.357, P=0.241; testing dataset: χ2=10.793, P=0.214). DCA curve (Figure 5C) showed similar and favorable clinical benefits across both datasets. These results collectively validated that this combined model exhibited a strong diagnostic performance and robust generalizability.

Table 3

Univariate and multivariate logistic regression analysis in the training dataset

Variable Univariable analysis Multivariable analysis
OR 95% CI P OR 95% CI P
Gender 1.572 0.989–2.499 0.056
Age 1.069 1.046–1.093 <0.001* 1.004 0.972–1.038 0.81
Smoking history 0.582 0.242–1.401 0.23
Tumor history 1.816 0.755–4.367 0.18
CEA 7.897 2.329–26.770 0.001* 1.637 0.313–8.544 0.56
NSE 1.433 0.631–3.257 0.39
SCC 0.947 0.406–2.211 0.90
CYFRA 21-1 2.593 1.213–5.547 0.014* 4.175 1.253–13.904 0.02*
Lobe location 1.034 0.888–1.204 0.67
Maximum diameter 1.355 1.268–1.447 <0.001* 1.247 1.143–1.361 <0.001*
Density type 8.728 5.396–14.117 <0.001* 6.604 3.519–12.393 <0.001*
Shape 2.677 1.691–4.238 <0.001* 0.865 0.401–1.866 0.712
Border 1.098 0.708–1.701 0.68
Spiculation 9.042 5.049–16.195 <0.001* 1.322 0.559–3.123 0.53
Pleural retraction 7.462 4.489–12.405 <0.001* 2.056 0.960–4.400 0.06
Lobulation 4.728 2.831–7.898 <0.001* 1.661 0.758–3.643 0.21
Air bronchogram 7.426 4.041–13.648 <0.001* 3.149 1.406–7.051 0.005*
Cavity 2.197 0.934–5.170 0.07
Constant 0.004 0.001–0.026 <0.001*

*, P<0.05. CEA, carcinoembryonic antigen; CI, confidence interval; CYFRA 21-1, cytokeratin 19 fragment; NSE, neuron-specific enolase; OR, odds ratio; SCC, squamous cell carcinoma antigen.

Figure 4 Nomogram of the combined model in the training cohort. For CYFRA211 and air bronchogram, 0 represents negative, and 1 represents positive. For density type, 0, 1, and 2 represent pure ground-glass nodule, part-solid nodule, and solid nodule, respectively. CYFRA 21-1, cytokeratin 19 fragment.

Table 4

Diagnostic performance of the combined model in the two datasets

Dataset AUC (95% CI) Accuracy Sensitivity Specificity PPV NPV P
Training 0.925 (0.897–0.953) 0.863 0.872 0.853 0.872 0.853 <0.001*
Testing 0.895 (0.829–0.961) 0.876 0.833 0.925 0.926 0.831 <0.001*

*, P<0.05. AUC, area under the curve; CI, confidence interval; NPV, negative predictive value; PPV, positive predictive value.

Figure 5 Performance of the combined model in training and testing cohorts. (A) ROC curve, (B) calibration curve, and (C) DCA in different cohorts. AUC, area under the curve; DCA, decision curve analysis; ROC, receiver operating characteristic.

Discussion

The 2021 fifth edition of the WHO Classification of Thoracic Tumors reclassified and reorganized lung tumors compared to the 2015 fourth edition, moving AAH and AIS out of the adenocarcinoma category and reclassifying them as precursor glandular lesions, while MIA remains classified under adenocarcinoma (4,5). This has sparked an extensive debate among Chinese experts: the reclassification of AIS raised concerns about whether AIS should no longer be considered a malignant tumor but rather a precancerous lesion, and whether its treatment should be adjusted accordingly to avoid overtreatment (21). However, international experts still recommend surgical resection and advocate sublobar resection due to its indolent nature (22). Since both AIS and MIA exhibit limited histological invasion, their 5-year recurrence-free probability after surgery is nearly 100%, with a very low risk of recurrence beyond 5 years and similarly favorable survival outcomes (6). This strongly supports the clinical value of distinguishing AIS and MIA from other lung adenocarcinomas. Furthermore, sublobar resection and lobectomy yield similar survival outcomes for AIS and MIA (15,16). To avoid overtreatment, sublobar resection (segmentectomy or wedge resection) is recommended for diagnostically challenging AAH, AIS, and MIA. In contrast, IAC requires lobectomy and lymph node dissection (23).

A population-based study in France found the incidence of SPNs to be 16.4–17.7% in males and 4.9–8.2% in females (24). The malignancy rate of SPN reaches 12% (25), with 60% of malignant SPNs being lung adenocarcinomas (26). Incidentally detected SPNs via CT in asymptomatic patients pose an increasingly common clinical challenge for radiologists in daily practice. The heterogeneity of lung adenocarcinoma leads to a wide variety of imaging presentations in SPNs (27). Based on different surgical treatment strategies, this study categorized lung adenocarcinomas and their precursor lesions presenting as SPNs into the invasive group (IAC) and the pre-invasive/micro-invasive group (AAH, AIS, MIA). By analyzing the tumor markers and CT radiological features, this study aimed to establish a non-invasive preoperative diagnostic prediction model to differentiate these two groups. To address the issue of data imbalance, the patients in four participating centers were paired and divided into the training dataset and testing dataset, which could make the study more representative.

There have been several related studies conducted previously. Feng et al. combined radiomics with traditional models to develop a nomogram for distinguishing between microinvasive and IAC in patients with solitary subsolid pulmonary nodules, achieving a strong performance in both training cohort (AUC: 0.943; 95% CI: 0.895–0.991) and validation cohort (AUC: 0.912; 95% CI: 0.780–1.000) (28). However, the small sample size raises concerns about bias and the reliability of results. Wang et al. established a combined model integrating intratumoral and peritumoral radiomics with CT imaging features to predict the invasiveness of subpleural ground-glass nodular lung adenocarcinoma with ≤50% solid component (AUC =0.912) (29). In contrast to the aforementioned studies, our investigation centers on lung adenocarcinomas manifesting as SPNs, with a more diverse spectrum of nodule types and pathological features. Additionally, no prior studies integrated the tumor markers and CT imaging features to diagnose SPN-presenting lung adenocarcinoma invasiveness. This multicenter study established a combined diagnostic model based on readily available laboratory and CT imaging data, demonstrating a consistently strong performance in both the training and testing cohorts, with AUCs of 0.925 (95% CI: 0.897–0.953) and 0.895 (95% CI: 0.829–0.961), respectively.

CEA, SCC, NSE, and CYFRA 21-1 are the most widely used tumor markers for primary lung cancer. Elevated lung cancer tumor markers can sometimes appear earlier than clinical symptoms, aiding in early diagnosis and predicting the pathological subtype (30,31). Increased serum levels of CEA, SCC, and CYFRA 21-1 are useful for diagnosing non-small cell lung cancer and estimating therapeutic efficacy (32-36). Among these, CEA levels are most significantly elevated in lung adenocarcinoma, demonstrating high sensitivity but low specificity, while the combined detection of CYFRA 21-1 and CEA could improve the diagnostic accuracy (37,38). Our study further confirmed that CEA and CYFRA 21-1 can effectively differentiate invasive lung adenocarcinoma from pre-invasive/micro-invasive lesions (P<0.05). In the training dataset, both univariate and multivariate analyses demonstrated that the elevated CYFRA 21-1 is an independent risk factor for predicting the invasiveness of solitary lung adenocarcinoma (OR: 4.175; 95% CI: 1.253–13.904; P<0.05).

In addition, CT features including density type (OR: 6.604; 95% CI: 3.519–12.393; P<0.001), maximum diameter (OR: 1.247; 95% CI: 1.143–1.361; P<0.001), and air bronchogram (OR: 3.149; 95% CI: 1.406–7.051; P=0.005) were identified as independent predictive factors. CT imaging features are crucial for the qualitative diagnosis of nodules (39). First, ground-glass opacity is associated with less aggressive histological subtypes, whereas the presence of solid components suggests a more invasive subtype (40). The qualitative density characteristics on CT help assess invasiveness (41). Second, larger nodule diameter usually correlates with a higher malignancy risk (42). Similarly, the larger the SPN diameter, the higher the malignancy potential of lung adenocarcinoma (43). Finally, the air bronchogram sign, which refers to visible aerated bronchi within the nodule, aids benign-malignant differentiation (43). Our study further confirmed that its presence can also predict the invasiveness of lung adenocarcinoma. These imaging features can be easily obtained through the non-contrast CT scans and are significantly effective for differential diagnosis.

This study has the following limitations. First, subjective bias may exist due to manual measurements and interpretation of imaging features. Second, the inclusion criteria of 5–30 mm nodules excluded sub-5 mm tiny nodules, which may introduce selection bias. Third, the limited sample size of the test set (n=113) may affect the statistical power. Fourth, lack of prospective validation. A prospective study with larger sample size and more precise imaging analysis techniques in the future is indispensable to enhance the reliability of the conclusions.


Conclusions

In conclusion, this study established and validated a clinically predictive model, combining the tumor marker (CYFRA 21-1) and CT imaging features (density type, maximum diameter, and air bronchogram), to perform a non-invasive preoperative differentiation between invasive and pre-invasive/microinvasive solitary lung adenocarcinoma lesions. This model showed favorable diagnostic accuracy and clinical value across cohorts, with good fit and robust generalizability. Given the widespread availability and affordability of CT and serological tests worldwide, this model can be easily implemented even in resource-limited regions. Therefore, it holds potential for clinical translation, providing a basis for precise individualized treatments.


Acknowledgments

None.


Footnote

Reporting Checklist: The authors have completed the TRIPOD reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-950/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-950/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-950/prf

Funding: This study was supported by the grants of National Natural Science Foundation of China (No. 82372069 and No. 82072041), National Key R&D Program of China (No. 2023YFC2413500 and No. 2024YFC2417805), and the Outstanding Youth Foundation of Hubei Province, China (No. 2023AFA107).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-950/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the institutional ethics committees of Union Hospital (No. 2025-0140), Tongji Hospital (No. TJ-IRB202401064), Jinshan Hospital (No. 2024-S48), and The First Affiliated Hospital of Zhengzhou University (No. 2024-KY-0862-001). Informed consent was waived due to the retrospective nature of the study.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.


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Cite this article as: Liu X, Wang D, Yang X, Yue X, Zheng C, Xia L, Kan X. A nomogram for preoperative prediction of invasiveness in solitary pulmonary adenocarcinoma: a multicenter study. J Thorac Dis 2025;17(10):8210-8223. doi: 10.21037/jtd-2025-950

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