Ann Thorac Surg 2003;75:1605-1606
© 2003 The Society of Thoracic Surgeons
Original article: general thoracic
Invited commentary
Cris A. Meyer, MDa,
Kenneth A. Kesler, MDa
a Departments of Radiology and Surgery, Thoracic Division, Indiana University School of Medicine, Indianapolis, IN46202, USA
e-mail: kkesler{at}iupui.edu
Following a retrospective review of their institution’s pathologic data from previously resected ground-glass opacity (GGO) lesions, Nakata and colleagues prospectively studied 33 patients who underwent thoracoscopic wedge resection of a pure (no solid component) GGO pulmonary lesion. Lesions were 1 cm or less in diameter and had not resolved after an average of 3.7 months. Only one GGO lesion pathologically demonstrated invasive adenocarcinoma with the remaining 32 lesions classified as either bronchoalveolar cell carcinoma (BAC) or atypical adenomatous hyperplasia (AAH). After a median follow-up of 18 months, they report neither evidence of local recurrence nor evidence of metachronous GGO lesions in these 33 patients. It is well-established that anatomic resection in the form of either lobectomy or pneumonectomy remains the standard surgical treatment for non-small cell lung cancer to minimize the risk of local recurrence in patients who have the cardiopulmonary reserve to tolerate such a procedure. The authors provide preliminary data to support the use of minimally invasive and parenchymal sparing surgery in this clinical scenario, which although currently relatively uncommon, will likely be encountered with more frequency given the increasing use of screening chest computed tomography (CT) scans.
These data, however, raise further questions of interest and importance. The first set of questions focus on the incidence and pathologic behavior of GGO lesions. How many GGO lesions were detected over the study interval that resolved during this relatively brief period of radiographic observation, and were therefore presumably secondary to infectious processes? In other words, what percentage of GGO lesions initially identified on screening CT scan did not ultimately undergo removal? It is also noteworthy that nearly 80% of patients in this series were "nonsmokers." How many screening CTs were obtained in "low-risk" patients to identify these select GGO abnormalities? If relatively few, one wonders about the true malignant potential of these GGO lesions and, in particular, the AAH pathologic subtype with the possibility that many of these incidental lesions remain indolent or even resolve over extended periods of time. On the other hand, if a relatively large number of screening CT’s were obtained, one wonders about the cost effectiveness of screening "low-risk" populations to identify "low-grade" neoplasms.
From a technical standpoint, the authors utilized preoperative needle localization for an unspecified number of "deeper" GGO lesions. Needle localization, while theoretically appealing for deeper pulmonary lesions, can be fraught with complications such as pneumothorax, or even worse, intraparenchymal hemorrhage prior to thoracoscopic removal. Determining the angle and depth of the localizing needle in relationship to a GGO lesion, which tend to have indistinct palpable margins, may also be difficult during thoracoscopy and therefore also potentially compromise surgical margins. It would seem that further study is needed to determine the efficacy of needle localization of GGO lesions prior to thoracoscopic removal, and the ability in general to widely excise relatively deeper GGO lesions with minimally invasive techniques.
Finally, there are issues related to CT scan follow-up after successful wedge resection of a GGO lesion. Because these are very slow growing "precancerous" and "cancerous" lesions with doubling times likely to be in excess of 24 months, the median 18-month follow-up in this study falls short to convincingly demonstrate the absence of local recurrence in these patients. Given the propensity of some GGO lesions to develop in multicentric locations, it will also be of interest to know how many of these 33 patients developed metachronous GGO lesions during late follow-up. Until the answers to these questions are known, these data as well as the known propensity of GGO lesions to be multicentric, would however support the use of minimally invasive and parenchymal sparing surgery for the diagnosis and treatment of small, peripheral, and pure GGO lesions which do not resolve after a reasonable period of radiographic observation.
