P1.03-072 Mediastinal Lymph nodes Staging by PET CT for Resectable Non-Small Cell Lung Cancer in a Tuberculosis Endemic Country

Abstract

Integrated 18 fluorine fluorodeoxyglucose (18F-FDG) PET-CT has shown somewhat variable sensitivity and specificity for nodal staging in tuberculosis endemic areas. This variation mainly because PET scans show falsely increased 18F-FDG uptake in inflammatory nodes, which may be observed in lymph nodes containing calcification or showing higher attenuations than those of surrounding great vessels on unenhanced CT scans. TB is a major health problem in India, incidence is around 2.1 million cases annually. The purpose of the study was to evaluate the efficacy of PET-CT for mediastinal nodal staging in non-small cell lung cancer (NSCLC) patients in a tuberculosis-endemic country. Prospective assessment of the diagnostic efficacy of integrated PET-CT for detecting mediastinal nodal metastasis was performed from February 2012 to February 2016. A total 160 patients underwent surgery for pathologically proven NSCLC. Patients who received chemotherapy or radiotherapy prior to surgery were excluded from study. Thus assessment of the diagnostic efficacy of integrated PET-CT for detecting nodal metastasis was performed in 46 patients (Male to Female ratio:4; mean age- 55 years). Patients underwent an integrated PET-CT examination and subsequent surgical nodal staging. One radiologist and 1 nuclear medicine specialist together prospectively evaluated PET-CT datasets. Nodes showing greater 18F-FDG uptake at PET without benign calcification or high attenuation >70 household unit (HU) at unenhanced CT were regarded as being positive for malignancy. All patients underwent hilar and mediastinal lymph nodes dissection according to the AJCC lymph node map (nodal stations 2R, 4R, 7, 8 and 9 for a right-sided tumor; 4L, 5, 6, 7, 8 and 9 for a left-sided tumor) after resection of the main tumor. Histologic nodal assessment results were used as reference standards. Of these 55 patients, 10 (20%) had a past history of pulmonary tuberculosis as determined by clinical or imaging studies. Of 230 mediastinal nodal stations evaluated in 46 patients, 5(2%) stations in 4(8%) patients proved to be malignant by histopathologic assessment. Mean number of lymph node stations evaluated were 5. On a per-nodal station basis, the overall sensitivity, specificity, accuracy, PPV, NPV of PET-CT were 60%, 97%, 96%, 38%,99% for mediastinal lymph nodes staging (N2) respectively. Integrated PET-CT provides high specificity and high accuracy, but low sensitivity for mediastinal staging of NSCLCs. The high specificity is achieved at the expense of sensitivity by interpreting calcified nodes or nodes with high attenuation at CT, even with high FDG uptake at PET, as benign in a tuberculosis-endemic region.