Cost, Risks, and Additional Diagnosis
Prior to the NLST, reports on lung cancer cost effectiveness were inconsistent, ranging from very favorable to unfavorable.[15–18] This was due to the variability in screening protocols, cost of LDCT, and uncertainty regarding the impact on mortality. A retrospective cost analysis of the NSLT estimated that annual LDCT cost an additional $1,631 per person and provided an additional 0.0316 life-years per person and 0.0201 quality adjusted life years (QALY) per person. The incremental cost effectiveness ratios (ICER) were $52,000/life-year gained and $81,000/QALY gained. This falls below the recommended $100,000 for efficacy and compares favorably with screening for breast, colon, and cervical cancer. Of note, this was conducted on the NSLT study population and the costs may be higher outside of the controlled environment of the study.
Radiation Exposure. Patients and physicians have limited understanding of true risks related to lung cancer screening. Increased radiation exposure is a fear because of its association with cancer development. The mean LDCT radiation dose in the NLST was 1.4 millisievert (mSv). This is compared with 7 to 8 mSv for a diagnostic chest CT and 0.1 mSv for a chest radiograph. The cancer risk from this very low radiation dose is small and can only be estimated on a population basis. It is estimated that yearly LDCT scanning from age 50 to 75 years will result in a 0.23 and 0.85% increased lifetime risk of lung cancer in men and women respectively.
False Positives. A far more common risk relates to the evaluation of false positive scans. Thirty-six percent of NLST participants had a positive scan, but only a small fraction (4%) were cancer. Greater than 90% were false positive but required further evaluation; for the majority, this was only an additional imaging procedure. One hundred and twenty-one patients (0.01%) in the chest radiograph group and 297 (0.03%) in the LDCT underwent surgery for false positive findings. One patient died following surgery for benign disease. This highlights that to make screening effective, false positives and invasive biopsies must be minimized without reducing benefit of early detection.
Anxiety. Prolonged nodule follow-up of nodules has the potential to cause stress and anxiety. Fear of a growing lung cancer should not be underestimated, but the anxiety associated with positive scans is not well studied. Two recent meta-analyses suggest that LDCT screening is associated with short-term psychologic discomfort but did not negatively impact health-related quality of life.[24,25]
Significant Incidental Findings
Significant incidental findings are unexpected findings and require clinical or imaging investigation before the next recommended screening study. In addition to early detection of lung cancer, LDCT screening provides an opportunity to detect cardiovascular disease, pulmonary disease, and extrapulmonary neoplasms, such as thyroid, breast, kidney, liver, esophageal, pancreatic, and mediastinal tumors. The reporting and management of incidental findings varies dramatically amongst screening trials. The Lung-RADS (lung imaging reporting and data system) reporting system now uses the "S" modifier to classify clinically significant nonlung cancer findings. In a recent study of 581 patients who received baseline LDCT, 45% of participants received an "S" modifier. Half of these were coronary artery calcification. An examination of interradiologist concordance of "S" modifier showed 42% agreement. Specific guidelines are needed to determine what is clinically significant and to improve reporting uniformity. The clinical relevance of the noncoronary significant findings is still controversial. In the NLST trial, 22.3% of certified deaths in the LDCT arm were due to extrapulmonary malignancies, compared with 22.9% of deaths from lung cancer.
Semin Respir Crit Care Med. 2020;41(3):447-452. © 2020 Thieme Medical Publishers