Diameter versus volumetry: A narrative review on current recommendations to measure and monitor screening detected lung nodules

Lung cancer (LC) is a leading cause of oncological death worldwide. Up to 70% of patients suffers from advanced disease at the time of diagnosis, which limits curative options. Early diagnosis of LC by means of low dose computed tomography (LDCT) has been proven effective by different LC screening (LCS) trials, which show a 20-30% mortality reduction in high-risk subjects. LDCT allows identification and longitudinal evaluation of pulmonary nodules (PNs), with subsequent stratification of LC risk based on their size and growth rate. Adequate management of screen-detected PN mostly relies on nodule density and sizing. Accurate size measurement is mandatory to determine the risk for malignancy, the recall rate and thus, the feasibility and the efficacy of LCS. Size and growth rate of PN can be determined by measuring either their diameter or volume. This narrative review article aims at reporting strengths and weaknesses of the two PN sizing approaches in LCS, and to discuss possible implications of PN size over- and underestimation.