Clinical Utility of Chromosomal Aneusomy in Individuals at High Risk of Lung Cancer

Introduction Low-dose computed tomography screening for lung cancer has a high false-positive rate with frequent discovery of indeterminate pulmonary nodules. Noninvasive biomarkers are needed to reduce false positives and improve risk stratification. A retrospective longitudinal evaluation was performed to assess chromosomal aneusomy in sputum by fluorescence in situ hybridization (CA-FISH) in four nested case-control studies. Methods Receiver operating characteristic analysis resulted in two grouped cohorts: a high-risk cohort (Colorado High-Risk Cohort and Colorado Nodule Cohort [68 case patients and 69 controls]) and a screening cohort (American College of Radiology Imaging Network/National Lung Screening Trial and Pittsburgh Lung Screening Study [97 case patients and 185 controls]). The CA-FISH assay was a four-target DNA panel encompassing the EGFR and v-myc avian myelocytomatosis viral oncogene homolog (MYC) genes, and the 5p15 and centromere 6 regions or the fibroblast growth factor 1 gene (FGFR1) and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha gene (PIK3CA). A four-category scale (normal, probably normal, probably abnormal, and abnormal) was applied. Sensitivity, specificity, and positive and negative likelihood ratios (LRs) (with 95% confidence intervals [CIs]) were estimated for each cohort. Results Sensitivity and specificity were, respectively, 0.67 (95% CI: 0.55–0.78) and 0.94 (95% CI: 0.85–0.98) for high-risk participants and 0.20 (95% CI: 0.13–0.30) and 0.84 (95% CI: 0.78–0.89) for screening participants. The positive and negative LRs were, respectively, 11.66 (95% CI: 4.44–30.63) and 0.34 (95% CI: 0.24–0.48) for high-risk participants and 1.36 (95% CI: 0.81–2.28) and 0.93 (95% CI: 0.83–1.05) for screening participants. Conclusion The high positive LR of sputum CA-FISH indicates that it could be a useful adjunct to low-dose computed tomography for lung cancer in high-risk settings. For screening, however, its low positive LR limits clinical utility. Prospective assessment of CA-FISH in the incidentally identified indeterminate nodule setting is ongoing in the Colorado Pulmonary Nodule Biomarker Trial.