Appropriate screening intervals in low-dose CT lung cancer screening

One of the pending challenges in the optimization of lung cancer screening by low-dose chest CT (LDCT) is the definition of the best screening regime. Currently, lung cancer screening is being implemented in routine clinical care in the United States, and other countries may follow in near future (1). The US Preventive Services Task Force recommends annual lung cancer screening by LDCT in high-risk individuals (aged 55 to 80 years who have a 30 pack-year smoking history and currently smoke or have quit within the past 15 years), based on the results of the National Lung Screening Trial (NLST) (2,3). This largest randomized-controlled LDCT lung cancer screening trial worldwide demonstrated a 20% decrease in lung cancer specific mortality in the intervention group, screened by three annual LDCTs, compared to the control group, screened by three annual chest radiographs (3). As a result of these findings, current lung cancer screening programmes include up to 25 annual LDCTs plus additional short-term follow-up LDCTs when indicated. However, the choice of a yearly CT scan has not been based on biological mechanisms, and it is questionable whether all persons eligible for lung cancer screening require annual screening (4). Recently, more and more evidence for a more personalized screening regime has become available. Selection of eligible participants at highest risk of lung cancer detection by a risk-prediction model has been shown to lead to more efficient lung cancer screening with higher cumulative lung cancer incidence and more early stage lung cancers detected (5). It is hypothesized that adding lung cancer risk based on LDCT characteristics to lung cancer risk of participant already enrolled in a screening program could help to identify a subset of participants at lower lung cancer risk based on their baseline screening CT who can safely be followed by a prolonged screening interval. This will improve the benefit-to-harm ratio and will lead to more efficient lung cancer screening programs. The aim of this review is to discuss current evidence on optimal screening intervals in LDCT lung cancer screening