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2002

2002 Role of PET in the Evaluation of Pulmonary Lesions and Preoperative Staging of Pulmonary Malignancy

Dr Chow Bing Fai, Ruttonjee and Tang Shiu Kin Hospital

Abstract Background
The investigation of pulmonary malignancy often requires multiple invasive procedures. Positron emission tomography (PET) is a new non-invasive means of diagnosing and staging lung cancer.

Objective
To evaluate the accuracy of PET in the diagnosis and pre-operative staging of lung cancer in Hong Kong.

Settings
A local regional chest hospital.

Methods
55 consecutive patients with indeterminate solitary pulmonary nodule (SPN) or pulmonary lesions referred for PET was analyzed retrospectively. Data on computer tomographic(CT) findings, tissue histopathology and SUVmax value of PET was collected.

Results
Malignant SPN was defined in 39 (71%) patients by sputum cytology (4), transthoracic tissue aspiration (15), bronchoscopy (14) and direct thoracotomy (6). Benign SPN was defined in 16 (29%) patients by tissue biopsy (1), lobectomy (1), lesions regression (3) or stability (11) for more than 2 years. In the SPN, the SUVmax values were significantly higher for malignant (meanj:SD, 6.95j:3.59) than benign nodules (1.77j:1.68). Using the cut off value of 2.5, the accuracy of PET on SPN was 88.1% (49/55) with a sensitivity of 92.3% (36/39) and specificity of 81.3% (13/16). The positive (PPV) and negative predictive value (NPV) was 92.3% (36/39) and 81.3% (13/16) respectively. Three false positive cases were identified (all were tuberculosis). Three false negative cases were found (all were stage I adenocarcinoma). In the nodal staging, the accuracy, sensitivity, specificity, PPV and NPV of PET was 86.7%, 75.0%, 90.9%, 75.0% and 90.9% respectively.

Conclusions
PET was sensitive but non- specific in classification of benign and malignant pulmonary nodules. In pre-operative mediastinal staging, PET is highly specific and mediastinoscopy could be avoided before surgery.

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