Pulmonary metastasis is seen in 20–54% of extra-thoracic malignancies [9]. Lung-RADS reporting is standardized per CT lung screening, which accounts for pulmonary nodules and other findings concerning carcinoma, as well as any significant incidental findings [10, 11].
The present study included 200 newly developed pulmonary nodules in 187 known cured cancer patients that were categorized by the lung-RADS calcification system into 6 sub-groups, 1-4A, 4B, and 4X, and we considered scores of 4A, 4B, and 4X as malignant. We found 86 lesions to be benign that were categorized as lung-RADS 1–3 scores. However, 8 of them were found to be malignant metastatic lesions (false negative) in line with histopathology and follow-up results. While we diagnosed 114 nodules as malignant lesions with lung-RADS 4A, 4B, and 4X scores, 21/114 proved to be of benign etiology (false positive): 6 inflammatory granulomas per histopathology results and 15 showed static appearance on LDCT chest follow-up after 18–24 months. Our findings were consistent with those of Caparica et al. [3], who conducted a similar study) on 228 patients and metastatic disease was found in 146 patients (64%). On biopsy, 60 patients (26.3%) were found to have a second primary lung tumor, while 22 patients (9.6%) were found to be cancer-free. Other series have also found different rates of malignant nodules on histologic analysis. In a large study with 1104 patients undergoing PNs resection, Mery et al. [12] observed a 63% malignancy rate in 337 patients with a previous cancer history. A lower rate by Khokhar et al. [13] discovered malignant pulmonary nodules in oncologic patients; 28% of small pulmonary nodules detected on the initial CT will increase in size, suggesting metastasis. However, Reginald et al. [14] concluded that in the majority of clinical settings, an interval increase in the size of a single pulmonary nodule is considered evidence of metastasis, this size increase tends to occur early, and follow-up CT in 3 and 6 months would be appropriate for further evaluation. On the opposite hand, Meng et al. [15] divided ground-glass nodules into three groups: benign disease (inflammations), pre-invasive group, and invasive group (adenocarcinoma) in line with the pathologic findings of type IV, strongly suggesting a high likelihood of malignancy, while Kim et al. [16] stated that pulmonary sub-solid nodules (SSNs) are frequently encountered within the screening CT with their main concern being lung adenocarcinoma and its precursors. Results from the National Lung Screening Trial showed that carcinoma screened by CT significantly reduced carcinoma mortality, and benign nodules were primarily confirmed by stability or shrinkage on repeat CT scans over a 2-year follow-up period [17]. Chung et al. [18] found that the typical false-positive rate was 7% for category 3 nodules, 7% for category 4A nodules, and 19% for category 4B nodules.
Lung-RADS may be a tool that facilitates standardized reporting and management of abnormal findings at LCS CT [8].
Our findings revealed that the lung-RADS arrangement had a high sensitivity of 92.08%, specificity of 78.79%, and accuracy of 85.50% in the diagnosis of pulmonary nodules in oncology patients, with 81.58% positive predictive value and 90.70% negative predictive value. These results were in agreement with McKee et al. [19], who said that ACR lung-RADS reduced the general positive rate from 27.6 to 10.6%. No false negatives were present within the 152 patients with > 12-month follow-up reclassified as benign. Applying ACR lung-RADS increased the positive predictive value for diagnosed malignancy in 1603 patients with follow-up from 6.9 to 17.3% and by Kessle et al. [20], who concluded that lung-RADS produced 9 false-positives and 16 false-negative findings, whereas VRC with a 5% threshold resulted in 29 false-positives and 10 false-negative findings. Overall sensitivity and specificity for lung-RADS was 58.0% and 98.0%, and for VRC with a 5% threshold was 73.7% and 93.5%, respectively (P = .313, P = .001, respectively).