[The volume and mass growth of persisted pulmonary nodules detected in low-dose CT screening and its influence factors].

Objective: To evaluate the changes of volume and mass of pulmonary nodules which were detected in low-dose computed tomography (LDCT) screening, and to analyze the influencing factors. Methods: This retrospective study analyzed the CT images of the participants who underwent at least two chest LDCT scanning from March 2009 to December 2015 in National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. The inclusion criteria was the nodule diameter ≥6 mm; the volume growth was defined as ≥20%. Fifty-one pulmonary nodules (PNs) were selected among 51 enrolled participants (26 men and 25 women). According to characteristic of nodule and risk stratification of participant, the nodules were classified into different groups (10 non-solid nodules, 17 part-solid nodules and 24 solid nodules; 14 PNs in high-risk group, 12 PNs in moderate-risk group and 25 PNs in low-risk group). The Lung-VCAR software was used to measure the diameter and volume of the PNs, and all nodules were calculated for the volume doubling time (VDT) and mass doubling time (MDT). Results: Among the 51 PNs, the diameter of 33 nodules increased more than 1.5 mm while 18 nodules increased less than 1.5 mm. The median VDT of part-solid nodules was 364 days, which was shorter than that of non-solid nodules and solid nodules (761 and 819 days, respectively), the differences were statistically significant (both P<0.05). The median MDT of part-solid nodules was 351 days, which was lower than that of non-solid nodules and solid nodules (772 days and 840 days, respectively). The difference was statistically significant (P<0.05). The median VDT and MDT of the pulmonary nodules in the high-risk group were 181 days and 256 days, respectively, which were lower than those in the low risk group (1 037 days and 1 035 days, respectively). VDT has good correlation with MDT (r=0.909, P<0.001). Conclusions: Both the characteristic of PNs and the risk status of the participants could affect the growth of nodules in LDCT screening. The part-solid nodules and high-risk group nodules grew relatively faster, which should be closely focused on. Compared with the two-dimensional diameter, the three-dimensional quantitative indicators (VDT and MDT) were more sensitive for nodule growth. The mass changes of part-solid nodules were earlier than that of volume.