The feasibility of low-dose CT for pulmonary metastasis in patients with primary gynecologic malignancy

Purpose To assess the feasibility of low-dose CT (LDCT) in the detection of pulmonary metastases in patients with primary gynecologic malignancies and also to compare the performance of chest digital radiography (DR) and LDCT for their delectability of pulmonary metastases, with use of standard-dose CT (SDCT) as the reference standard. Materials and methods Thirty female patients with primary gynecologic malignancies (age range, 20–76 years; mean age, 50 years) underwent DR, noncontrast LDCT and contrast-enhanced SDCT, which were performed within an interval of 2 weeks. We used lung nodule, mediastinal lymphadenopathy (>10 mm in the short axis) and pleural changes (including effusion, irregular thickening, or nodularity) as the cardinal imaging findings of lung metastases. A five-point scoring system was designed to indicate the probability of lung metastasis from primary gynecologic malignancies. The five-point scores of DR, LDCT, and SDCT were analyzed by receiver operating characteristic (ROC) curve. Results SDCT probability scores of +2 and −2 were set to indicate true positive and true negative for pulmonary nodule, mediastinal lymphadenopathy, and pleural effusion, respectively. All the areas under the ROC curve of LDCT appeared to be larger than those of DR{pulmonary nodule: 0.96 [95% confidence interval (CI): 0.92–1.01] vs. 0.74 [95% CI: 0.57–0.91], 0.82 [95% CI: 0.70–0.95] vs. 0.61 [95% CI: 0.50–0.77]; mediastinal lymphadenopathy: 0.98 [95% CI: 0.93–1.03] vs. 0.90 [95% CI: 0.79–1.01], 0.94 [95% CI: 0.82–1.06] vs. 0.66 [95% CI: 0.44–0.88]; and pleural effusion: 0.98 [95% CI: 0.93–1.03] vs. 0.56 [95% CI: 0.29–0.82], 0.90 [95% CI: 0.74–1.05] vs. 0.46 [95% CI: 0.23–0.68]}. Conclusion The performance of LDCT were comparable to those of SDCT and superior to those of DR for detection of pulmonary nodule, mediastinal lymphadenopathy, and pleural effusion. By using LDCT, there was no need of intravenous contrast injection and less radiation exposure. We propose a protocol including standard-dose abdominal CT and low-dose chest CT for the initial and follow-up stagings of primary gynecologic malignancy. The use of chest DR is unnecessary.