Elsevier

Lung Cancer

Volume 45, Issue 1, July 2004, Pages 19-27
Lung Cancer

Evaluation of F-18 fluorodeoxyglucose (FDG) PET scanning for pulmonary nodules less than 3 cm in diameter, with special reference to the CT images

https://doi.org/10.1016/j.lungcan.2004.01.009Get rights and content

Abstract

Background: While pulmonary nodules can be substantially divided into solid and ground-glass opacity (GGO) ones on CT image, they have different biological natures which could cause false positive or false negative to diagnose malignancy on positron emission tomography with fluorodeoxyglucose (FDG-PET). To determine the effectiveness of PET for small pulmonary nodules, the nodules were classified into solid and GGO ones, of which results were compared with the data of PET scans. The lower limit size of nodules for PET imaging was also evaluated. Methods: Prospective FDG-PET scans were undertaken for 136 non-calcified nodules less than 3 cm in diameter. CT density histograms were made for each nodule to classify into solid and GGO ones. Results: Eighty-one nodules were malignant and 55 were benign. All of the 20 nodules less than 1 cm in diameter (n=8 in malignant, n=12 in benign), were negative on PET regardless of the histology. In the 116 nodules 1–3 cm in diameter (n=73 in malignant, n=43 in benign), there were 15 false negative and 15 false positive nodules, with a sensitivity of 79% and specificity of 65%. CT density histograms showed 101 solid nodules (n=63 in malignant, n=38 in benign) and 15 GGO nodules (n=10 in malignant, n=5 in benign). All of the 10 malignant nodules with GGO images were histologically well-differentiated adenocarcinoma and 9 of them (90%) were false negative on PET. Four of the 5 (80%) benign nodules with GGO images were focal pneumonia with well-preserved air spaces, causing false positive on PET. Sensitivity and specificity for nodules with GGO images were 10 and 20%, respectively, which were significantly lower than 90 and 71% for nodules with solid images (P<0.001). Conclusion: Pulmonary nodules which are less than 1 cm in size or show GGO images on CT cannot be evaluated accurately by PET.

Introduction

In recent years, low-dose helical computed tomography (CT) have enabled the detection of small peripheral pulmonary nodules [1], [2], [3]. Despite developments in CT technology, there are still a significant number of cases in which surgical resection is needed to differentiate lung cancer from benign lesions [4]. On the other hand, recent advances in positron emission tomography (PET) with 2-deoxy-2-fluoro-[F-18]-d-glucose (FDG) has made a significant contribution to differentiate between benign and malignant nodules, and several reports have suggested that PET examinations reduce the number of patients with indeterminate nodules undergoing unnecessary surgical biopsy [5], [6], [7], [8], [9]. However, FDG-PET is neither usually specific nor sensitive, particularly for small pulmonary nodules, because low-grade malignant tumor such as bronchiolo-alveolar carcinoma and carcinoid are frequently negative for FDG-PET due to their low glucose metabolism, while active inflammation sometimes showed positive due to their high glucose metabolism [5], [6], [10], [11], [12], [13], [14], [15]. To clarify the effectiveness of FDG-PET, it is necessary to examine the CT images of small pulmonary nodules that are false positive or false negative for FDG-PET.

Both malignant and benign pulmonary nodules can be substantially classified into ground-glass opacity (GGO) and solid ones on CT. For the GGO nodules, focal pneumonia, atypical adenomatous hyperplasia (AAH) and bronchiolo-alveolar carcinoma could be differential diagnoses [16], [17]. For the solid nodules, granuloma, benign lung tumor, and malignant tumors with solid growth could be differential diagnoses. Because those nodules have different biological natures, FDG-PET could show different findings. Recently, we have found that a CT density histogram can clearly divide lung adenocarcinomas into GGO and solid ones on CT images and can also predict lymph node metastasis and tumor invasiveness [18]. In the present study, to clarify the effectiveness of FDG-PET for pulmonary nodules less than 3 cm in size, we classified them into GGO and solid nodules with using a CT density histogram and compared the results with the data of FDG-PET.

Section snippets

Materials and methods

Between December 2001 and August 2003, prospective FDG-PET and CT scans were undertaken for 151 non-calcified pulmonary nodules less than 3 cm in diameter, which were consulted for surgical treatment or surgical biopsy on the Department of Thoracic Surgery of Saiseikai Central Hospital. After taking an informed consent, FDG-PET scan was performed at the Nishidai Clinic within 2 weeks after CT scan was done. Of the 151 nodules, 136 could be diagnosed as malignant or benign, while the remaining 15

Results

Mean sizes were 1.9±0.7 cm in the 81 malignant nodules and 1.4±0.7 cm in the 55 benign nodules, of which difference was not significant. Table 1 showed the histological type and sizes (<1 cm versus 1–3 cm) of malignant nodules. Of the 81 malignant nodules, 78 were diagnosed by surgical resection and the remaining 3 were by bronchoscopic or needle biopsy. Histologically, 68 nodules were diagnosed as primary lung cancer and 13 as metastatic lung cancer.

Table 2 showed the kind of diseases and sizes (<1

Discussion

There are few data about the lower limit size of pulmonary nodules that can be correctly identified by PET imaging. A meta-analysis for 1474 nodules by Gould et al. showed that in the eight nodules less than 1 cm in diameter, three were true positive, two were true negative, and three were false negative [20]. The present study showed that all of the eight malignant nodules less than 1 cm were false negative. The spatial resolution of current generation of PET scanners is 7–8 mm, which can hardly

References (26)

  • E.F Patz et al.

    Focal pulmonary abnormalities: evaluation with F-18 fluorodeoxyglucose PET scanning

    Radiology

    (1993)
  • N.C Gupta et al.

    Probability of malignancy in solitary pulmonary nodules using fluorine-18-FDG and PET

    J. Nucl. Med.

    (1996)
  • S.S Gambhir et al.

    Analytical decision model for the cost-effectiveness management of solitary pulmonary nodules

    J. Clin. Oncol.

    (1998)
  • Cited by (0)

    View full text