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ORAL 11 - Clinical Trials 1 (ID 100)
- Event: WCLC 2015
- Type: Oral Session
- Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
- Presentations: 1
ORAL11.07 - Computed Tomography (CT) Characteristics Associated with the Proposed IASLC/ITMIG TNM Pathologic Staging System for Thymoma (ID 1603)
10:45 - 12:15 | Author(s): A.N. Leung
Preoperative CT imaging assists in the management of thymic malignancies (TMs), discerning resectability and the need for neoadjuvant chemotherapy. Here, we examine preoperative CT imaging characteristics in relation to the newly proposed IASLC/ITMIG TNM pathologic staging system for TMs.
Inclusion criteria for this retrospective study were as follows: 1) diagnosis of thymoma, thymic carcinoma, or thymic carcinoid, 2) definitive primary surgery performed at Stanford University, and 3) pretreatment CT imaging available for review. From 01/1997-03/2015, we identified 119 TM patients who had surgery, and 47 TM patients met all inclusion criteria. The most common reason patients were excluded was for either a missing pretreatment CT (outside imaging not routinely uploaded until 2008) or having surgery for biopsy or recurrent disease. The radiologist (D.T.) was blinded to clinical data, and examined baseline CT imaging per the International Thymic Malignancy Interest Group (ITMIG) standard report terms: contour, calcification, internal density, size of longest diameter, infiltration of mediastinal fat, abutment of mediastinal vessels, vascular endoluminal invasion, abutment/invasion of mediastinal structures, elevated hemidiaphragm, pleural nodules, pleural effusion, mediastinal lymph node enlargement. A univariate analysis and a Lasso regularized general transformation prediction model were performed with all variables to examine the association with pathologic IASLC/ITMIG TNM stage (p<0.05 significant; p<0.10 trend).
Of 47 TM patients, 9 received neoadjuvant chemotherapy. IASLC/ITMIG pathologic stage included 35 I, 1 II, 7 IIIA, 2 IIIB, 1 each of IVA and IVB. By T stage, there were 36 T1 (encapsulated or unencapsulated+extension into mediastinal fat or mediastinal pleura), 1 T2 (pericardium), 8 T3 (lung, brachiocephalic vein, SVC, chest wall, phrenic nerve, or hilar pulmonary vessels) and 2 T4 (aorta, arch, main pulmonary artery, myocardium, trachea, or esophagus). Only one patient each had N2 and M1a disease (separate pleural or pericardial nodule). Histologies included 5 A/micronodular thymoma, 13 AB, 5 B1, 14 B2, 5 B3, and 5 C/carcinoid. There was a significant positive association with aggressive histology and higher stage (OR=10.0;p=0.02). The following CT characteristics had a statistically significant positive association with higher stage (stage 1 vs. others, T1 vs. others) in a univariate analysis: lobulated contour, infiltration of mediastinal fat, invasion of mediastinal structures, vascular endoluminal invasion, elevated hemidiaphragm. There was a trend for higher stage with larger size and the presence of calcification. In a prediction model, vascular endoluminal invasion and elevated hemidiaphragm were the most important for predicting higher stage followed by invasion of mediastinal structures>abutment of mediastinal vessels>calcification>lobulated contour> mediastinal lymph node enlargement. When excluding clearly invasive CT characteristics, only abutment of mediastinal vessels was significantly associated with higher stage.
Preoperative CT characteristics, especially those indicating clear invasion, are most useful in delineating more advanced stage disease by ITMIG/IASLC criteria in TMs. Other primary tumor characteristics including contour, calcification, and abutment of mediastinal vessels are moderately helpful. This study is limited by the small sample size, the predominance of stage I disease, the inclusion of patients who received neoadjuvant chemotherapy, and the inherent bias of a definitive surgically treated population.
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