All patients underwent routine evaluation by interventional radiologists prior to MWA, including medical history review, physical examination, laboratory tests, and relevant imaging studies. Clinical staging was performed using thoracoabdominal contrast-enhanced CT or positron emission tomography/computed tomography (PET/CT). Anticoagulant and antiplatelet medications were temporarily discontinued for 1 to 7 days, depending on the type of medication. All patients also underwent routine complete blood count, coagulation function tests, biochemical tests, and an electrocardiogram before MWA.

A comprehensive pulmonary function assessment was performed for all patients in accordance with the guidelines established by the American Thoracic Society (ATS) and the European Respiratory Society (ERS) (14). Pulmonary function indicators—including forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), and maximum voluntary ventilation (MVV)—were measured for all patients. To account for differences in gender, age, height, and weight, both percent predicted values and raw data were used for comparison. ATS/ERS guidelines (2005/2019 editions) categorize ventilatory impairment into five grades: Mild (70% ≤ FEV₁%pred ≤ 80%), Moderate (60% ≤ FEV₁%pred ≤ 69%), Moderate-to-severe (50% ≤ FEV₁%pred ≤ 59%), Severe (35% ≤ FEV₁%pred ≤ 49%), and Very severe (FEV₁%pred < 35%) (15). The study was conducted without supplementary oxygen.

Clinical data of 2,150 NSCLC patients treated with MWA between January 2018 and December 2024 were retrospectively analyzed. The inclusion criteria were as follows: (1) preoperative pulmonary function tests were performed; (2) histopathologically confirmed stage I NSCLC; (3) ablation margin > 5 mm; (4) lesions confined to the lung (unilateral or bilateral); and (5) age ≥ 18 years with an Eastern Cooperative Oncology Group (ECOG) performance status (PS) score ≤ 2. Exclusion criteria were: (1) regional lymph node metastasis or distant metastasis confirmed by contrast-enhanced CT, PET-CT, or contrast-enhanced magnetic resonance imaging; (2) receipt of other treatments (e.g., radioactive particle implantation, radiotherapy) either during the same admission or at different admissions; and (3) missing follow-up data. Among routine pulmonary function parameters, MVV is the most reliable indicator of pulmonary reserve function. It is generally accepted that surgery is safe when MVV exceeds 70% of the predicted value. Additionally, both FEV₁ and diffusing capacity for carbon monoxide (DLCO) are recognized as independent prognostic factors (16). Typically, surgical resection is not recommended for patients with a preoperative FEV₁% predicted < 50%, or a predicted postoperative FEV₁ or carbon monoxide transfer factor < 40% (17, 18). Therefore, we concluded that mild pulmonary dysfunction had no significant impact on patient prognosis. In this study, the observation group included 42 patients with moderate-to-severe pulmonary dysfunction (defined by MVV < 70% or FEV₁ ≤ 59%), while the control group included 106 patients with normal lung function who met the study criteria. This retrospective study was approved by our institutional review board (KYLL-202408-026), which waived the requirement for informed consent. Additionally, all patients provided written informed consent prior to MWA.

MWA was performed using the ECO-100C device, which complies with the registration standard YZB/Country 3388–2011. The microwave transmission frequency was set at 2450 ± 50 MHz, with an adjustable output power range of 0–150 W. The microwave antenna had an effective length of 130–180 mm and an outer diameter of 15G–18G, and was equipped with a water-circulating cooling system to maintain a low surface temperature. CT imaging was utilized both to guide the MWA procedure and to assess its outcomes.

Before the procedure, the patient’s position (supine, lateral, prone, etc.) was determined via CT image analysis, and body surface marking lines were placed. The exact level and location of the lesion were identified using CT scans, and a planned needle insertion path was established. The entire procedure was performed under aseptic conditions, with local anesthesia administered at the puncture site. Under CT guidance, the ablation needle was carefully advanced into the lesion. A cable was then connected to link the ablation needle with the microwave generator and cooling circulation tube. Ablation duration and power levels were tailored to factors including lesion size, observed changes in the lesion, and patient tolerance. After MWA, an additional CT scan was performed to confirm that the ablation zone extended beyond the lesion area by a 5–10 mm margin. Following the patient’s safe transfer back to the ward, routine monitoring of heart rate, blood pressure, and oxygen saturation was initiated. A chest CT scan was scheduled 24–48 hours post-MWA for further evaluation (an example is shown in Figure 1).

Patients were hospitalized for MWA and subsequent observation. Immediately after ablation, a chest CT was performed to assess the completeness of ablation and detect potential complications (e.g., pneumothorax, hemorrhage, pleural effusion). Technical success was defined as complete tumor coverage by the ablation zone with an adequate margin, confirmed by the immediate post-procedure CT scan. If ablation was successful and no urgent complications occurred, patients were transferred to the ward for observation. During this period, postoperative infections and wound pain were monitored, along with routine checks of heart rate, blood pressure, and oxygen saturation. Another chest CT was conducted 24–48 hours post-MWA; patients were discharged 2–3 days later if no further treatment for complications was required. Follow-up chest CTs were scheduled at 1, 3, 6, and 12 months post-procedure, with subsequent check-ups every 6 months.

The primary endpoints were postoperative complications and length of hospital stay. Complications were graded using the standardized Society of Interventional Radiology (SIR) system (19). Patients who died within 30 days post-procedure were categorized under SIR classification F. Major complications (corresponding to SIR classifications C–E) were defined as events causing significant morbidity and disability that required blood transfusions or interventional drainage; all other complications were classified as minor. The secondary endpoint was progression-free survival (PFS), defined as the time from the date of MWA treatment to the first occurrence of local tumor progression or distant metastasis, whichever came first.

Categorical data were compared using the χ² test, and continuous data were compared using the t-test. Kaplan-Meier survival curves were utilized for univariate analysis. A p-value < 0.05 was considered statistically significant. All statistical analyses were performed using SPSS software (version 27; SPSS, Inc., Chicago, IL, USA).

Among 663 stage I NSCLC patients who underwent MWA and had available lung function data, 148 were ultimately included in the analysis. The observation group and control group comprised 42 patients (42/148, 28.38%) and 106 patients (106/148, 71.62%), respectively (Figure 2). All patients had pathologically confirmed diagnoses; patient and tumor characteristics are detailed in Table 1. The 42 patients in the observation group collectively underwent 42 MWA procedures, treating a cumulative total of 48 lesions. Two cases required the simultaneous use of two ablation needles due to large lesion volumes, while six cases involved the simultaneous ablation of two lesions during a single treatment session. The control group comprised 106 patients who collectively underwent 106 MWA procedures, cumulatively treating 114 lesions. Among these, four cases required the simultaneous use of two ablation needles due to larger lesion volumes, while eight cases underwent the simultaneous ablation of two lesions during a single treatment session.

Thirty-one patients (31/42, 73.81%) presented with ≥ 1 comorbidity. The principal comorbidities included hypertension (19/42, 45.24%), coronary artery disease (15/42, 35.71%), emphysema (22/42, 52.38%), chronic obstructive pulmonary disease (16/42, 38.10%), and diabetes mellitus (3/42, 7.14%). Analysis of the association between smoking and various complications indicated that smoking exhibited a statistically significant correlation with emphysema and chronic obstructive pulmonary disease (p < 0.05). Preoperatively, the predicted FEV₁ values ranged from 23.09% to 78.63% of predicted, with a mean of 56.43 ± 13.49% of predicted. MVV ranged from 31.32% to 69.82% of predicted, with a mean of 53.31 ± 12.53% of predicted (Table 2).

The incidence of adverse events in the observation group (42.86%, 18/42) was slightly higher than that in the control group (33.96%, 36/106), with no statistically significant difference (p = 0.4099). No procedure-related deaths occurred within 30 days post-MWA in either group. The grading of adverse events in the two groups is presented in Table 3. The mean length of hospital stay was 5.86 days in the observation group and 5.89 days in the control group, with no significant difference between the two groups (p = 0.9757).

Cox regression analysis incorporated vital capacity (VC, % predicted), FVC(% predicted), FEV₁(% predicted), FEV₁/FVC ratio, FEV₁/VC ratio, and MVV (% predicted). Univariate analysis indicated that patients with FEV₁ (percentage of predicted value) < 55% and FEV₁/VC < 70 were more prone to postoperative complications; however, multivariate analysis revealed no statistically significant differences (Table 4).

The median follow-up duration was 25.5 months (range: 10–53 months) for the observation group and 22 months (range: 10–65 months) for the control group, with no statistically significant difference between the two groups (p = 0.1478). No patients were lost to follow-up.

In the observation group, the median progression-free survival (PFS) was 39 months, with 1-year and 3-year PFS rates of 94.9% and 68.7%, respectively. In the control group, the median PFS was 44 months, with 1-year and 3-year PFS rates of 98.1% and 72.3%, respectively. However, the difference in PFS between the two groups was not statistically significant (p = 0.526; Figure 3).

Cox regression analysis included variables such as gender, age, smoking history, pathology, tumor size, vital capacity (VC, % predicted), FVC(% predicted), FEV₁(% predicted), FEV₁/FVC ratio, FEV₁/VC ratio, and MVV (% predicted). Both univariate and multivariate analyses revealed no statistically significant associations between these variables and PFS (p > 0.05; Table 5).