Sublobar Resection of Ground Glass Opacity—Great Data, but can I have More?
Authors: Frank C. Detterbeck
Journal: Journal of Thoracic Oncology (2011)

I read with great interest the article by Susuki et al.1Suzuki K Teruaki K Takashi A et al.A prospective radiological study of thin-section computed tomography to predict pathological noninvasiveness in peripheral clinical IA lung cancer (Japan Clinical Oncology Group 0201).J Thorac Oncol. 2011; 6: 751-756Crossref PubMed Scopus (403) Google Scholar and commend the authors for applying formal scientific methods in a prospective study to the issue of selection of patients for sublobar resection. These investigators and others from Japan have led the world in better defining the management of these patients. Nevertheless, I wish they had reported a few more details. From a statistician's point of view, sensitivity and specificity are good measures, but these do not lend themselves well to prospective application to an individual patient, which is the problem faced by the clinician. Specificity tells us how often the radiographic assessment will be positive for invasion in a cohort of patients in whom it is already known that they all have invasion.2Mandrekar JN Simple statistical measures for diagnostic accuracy assessment.J Thorac Oncol. 2010; 5: 763-764Crossref PubMed Scopus (36) Google Scholar A clinician, of course, does not know whether the patient has or does not have invasion preoperatively and only knows that the radiographic assessment has been either negative or positive. Thus, the clinician needs to know how often the assessment of “radiographically noninvasive” is falsely negative. This requires knowledge of the false-negative (FN) rate of the test result (or, as some prefer, the less intuitive term negative predictive value). Although the FN or false-positive rate is sometimes criticized for being influenced by the prevalence, this effect primarily occurs at extremely high or low prevalence (not in the range of prevalence among the patients in this study). As I calculate the results for all patients (regardless of size), the FN rate is 5%, 9%, and 7% for the C/T ratio, tumor disappearance ratio, and visual estimation methods, respectively. I wish the authors would report the FN rates for the three methods for tumors less than 2 cm. They have not provided enough data to allow this calculation to be made. In addition, although vascular invasion and lymphatic invasion have been widely viewed as surrogate markers for tumor dissemination to nodes or distant sites in Japan, this has been less well adopted in other parts of the world. Furthermore, I would argue that the issue in question is local spread (i.e. nodal metastasis) when considering lobar versus sublobar resection (if distant metastasis has occurred, it will not be influenced by the extent of local resection). Therefore, I think that focusing on a surrogate such as vascular or lymphatic invasion may not be as relevant as the actual occurrence of nodal metastasis. I wish the authors would specifically report the incidence of nodal involvement for tumors with a C/T ratio, tumor disappearance ratio, and visual estimation ratio of less than 0.5 (for lesions of all sizes as well as only those <2 cm). Once again, I wish to commend the authors for their substantial contributions to the clinical science of lung cancer.