As low-dose computed tomography (LDCT) is increasingly popular, the possibility of detecting ground-glass nodules (GGN) has also increased significantly, which was uncommon in the era of chest radiography as a regular health examination. Although the term GGN can be focal interstitial fibrosis, inflammation, hemorrhage and malignancies, we mainly focus on GGN that is pathologically malignant. A substantial proportion of GGNs detected at screening CT are transient [1]. It is important to avoid overtreatment of transient GGNs. The possibility of spontaneous regression of newly diagnosed GGN should always be considered before invasive treatment is decided. Several sets of guidelines are already available for the management of GGNs found on CT scans or via CT screening [2,3]. Obviously, there are differences in the recommendations of each guideline for some specific scenarios. One of the important reasons is that the correlation between radiographic appearance and histologic diagnosis is far from reliable [4]. Some people simply thought GGN referred to the site without blocking of alveolar cavity pathologically, and ground-glass opacity (GGO) components therefore represented the lepidic growth pattern of adenocarcinoma. However, both lepidic and non-lepidic growth patterns can present as GGNs on CT images [5]. So, GGO is a rather unspecific radiologic feature involving various pathologic conditions. The radiologic feature of GGO has a significant impact on clinical results. Several studies have revealed that the presence of a GGO component was a significantly favorable prognostic factor in early-stage NSCLC [6,7]. In Fu’s study, the 5-year RFS rates were 100% in the pure-GGN group no matter what histological type [8]. Such excellent prognosis naturally makes people think that it is not only the result of surgery, but also that these lesions might be indolent tumors even in the absence of any kind of treatment. Concerns have been raised about the possibility that premature surgical resection may represent‘overtreatment’. This is a good understanding of why Dr. Sepesi takes timing and indications for resection as an important issue for the treatment of GGN [9]. Although the precise surgical indications have not been determined, for obvious reasons a higher ratio of solid component need resected more urgently. The presence of a solid component is associated with a much higher risk for invasive adenocarcinoma [10]. However, there were different measurement results using different attenuation thresholds in regard to defining the solid or ground-glass components. Visual assessment of nodule morphologic structure on chest CT images Is still commonly used in clinical practice. However, interobserver and intraobserver discrepancies in nodule categorization cannot be ignored, especially disagreement on the size and presence of a solid component may lead to different management in the majority of cases with such discrepancies [11]. In order to evaluate the growth rate of GGNs in an accurate, reproducible, and sensitive manner, some measures on three-dimensional volumetry, such as volume doubling time (VDT) and mass doubling time (MDT), are getting more and more applications. High-grade invasive tumors show significantly shorter VDTs and MDTs than do low-grade invasive ones [12]. If the measurements of VDT and MDT can be popularized, they have the potential to become important references for evaluating GGN surgical indications. Furthermore, since the framework combining radiomics with deep learning (RDL) has the potential to predict high-grade lung adenocarcinoma, RDL might be a supplemental tool to screen high-risk subgroup in GGN patients for pathologists in the future [13]. Given the low aggressiveness of GGNs, it has been proposed that some GGNs meeting certain conditions could be cured by a limited surgical resection instead of a major lung resection. The trial of JCOG 0201 made a lot of exploratory work [14,15]. Long-term survival of patients in the trial of JCOG 0201 revealed that radiologic criteria of a consolidation/tumor ratio (CTR) ≤0.25 and a size≤ 2.0 cm or CRT ≤0.50 and a size ≤ 3.0 cm were both able to define a homogeneous subgroup with an excellent prognosis. Whether these radiologic criteria can be validated, we need to wait for the results of some prospective clinical trials, such as JCOG1211 [16] and GALGB140503 (NCT00499330). In term of surgical extent, the extent of lymphadenectomy is also an important issue. In Zhang’s study, there was no lymph node metastasis in GGN patients with CTR≤0.50, regardless of the tumor size [17]. This raises the question as to whether lymph nodes dissection is necessary in patients whose CT features manifest as GGO prominently. In summary, the decision to treat GGNs must consider both the aggressiveness of nodules and competing risks. Although more and more evidence come from retrospective studies on sublobar resection, high-quality evidence is needed to support a paradigm shift in clinical practice. There will be an ever-increasing tumor localization technology development to facilitate care for surgical management of GGNs. GGN, Surgery, Management
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Jun 9, 2021
Francis Vergunst + 7
Open Access
