The role of volume and mass doubling times of pulmonary pure ground glass nodules in differentiating invasive adenocarcinomas from minimally invasive adenocarcinomas and preinvasive lesions

Abstract

Objective To evaluate volume doubling time (VDT) and net mass doubling time of tumor (nMDT) of pulmonary pure ground glass nodules (PGGN) of different pathological types and to investigate whether VDT and nMDT can help to differentiate invasive pulmonary adenocarcinomas from minimally invasive adenocarcinomas and preinvasive lesions. Methods Fifty-one pathologically confirmed pGGNs in 46 patients were retrospectively evaluated, in whom at least two HRCT scans were obtained preoperatively (median scan times, 3 times; range, 2—6 times) with 1-month or longer follow-up interval(median follow-up interval, 251 days; range, 30-1 552 days). According to the rechecked results of the postoperative pathological section, 51 pGGNs were divided into two groups: group A, invasive adenocarcinoma (IAC), 30 pGGNs (58.8%); group B, 21 pGGNs (41.2%), including 8 minimally invasive adenocarcinoma (MIA), 7 adenocarcinomas in situ (AIS) and 6 atypical adenomatous hyperplasia (AAH). The volume, cumulative percentage of volume growth and VDTs of pGGNs were automatically acquired by Lung VCAR (advantage windows 4.6, GE HealthCare). Subsequently, the mass, cumulative percentage of mass growth and nMDTs of pGGNs were calculated. The count data and measurement data between two groups were compared using Fisher exact probability and Mann-Whitney U test, respectively. A pairwise comparision were performed by using Wilcoxon signed-rank test. Subsequently, the receiver operating characteristic (ROC) curve was used to determine the optimal cut-off values of VDT and nMDT for the differential diagnosis of IAC and MIA/AIS/AAH, and calculated the area under the curve (AUC). Results The median VDT and nMDT of 51 pGGNs were 1 854.11 days (range, 165.22—+∞ days) and 1 138.45 days (range, 95.92—+∞ days), respectively. The median nMDT was shorter than the median VDT, and the difference was significant (Z=-2.444, P=0.015). The median VDTs of IAC and MIA/AIS/AAH were 847.07 days (165.22—+∞ days) and 4 460.09 days (691.14—+∞ days), respectively. The median nMDTs of IAC, MIA/AIS/AAH were 769.93 days (95.92—+∞ days) and 3814.77 days (611.56—+∞ days), respectively. The median VDT and nMDT of IAC were significantly shorter than those of MIA/AIS/AAH (Z=-3.443,-3.860, P<0.01, respectively). Differentiating IAC from MIA/AIS/AAH, the optimal cutoff value of VDT was 2095.86 days (sensitivity, 71.4%; specificity, 80.0%), the optimal cutoff value of nMDT was 1 169.77 days (sensitivity, 81.0%; specificity, 76.7%). Conclusions In pulmonary pGGNs, IAC showed significantly shorter VDT and nMDT than MIA/AIS/AAH. When VDT is shorter than 2 095.86 days or nMDT is shorter than 1 169.77 days, IAC is suggested. Key words: Lung neoplasms; Tomography, X-ray computed; Ground glass nodule; Volume doubling time; Mass doubling time