Comparison of 18F-FDG PET/CT and MDCT for staging/restaging of non-small cell lung cancer

Additional Value of PET and CT Image-Based Features in the Detection of Occult Lymph Node Metastases in Lung Cancer: A Systematic Review of the Literature

Lung cancer represents the second most common malignancy worldwide and lymph node (LN) involvement serves as a crucial prognostic factor for tailoring treatment approaches. Invasive methods, such as mediastinoscopy and endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA), are employed for preoperative LN staging. Among the preoperative non-invasive diagnostic methods, computed tomography (CT) and, recently, positron emission tomography (PET)/CT with fluorine-18-fludeoxyglucose ([¹⁸F]FDG) are routinely recommended by several guidelines; however, they can both miss pathologically proven LN metastases, with an incidence up to 26% for patients staged with [¹⁸F]FDG PET/CT. These undetected metastases, known as occult LN metastases (OLMs), are usually cases of micro-metastasis or small LN metastasis (shortest radius below 10 mm). Hence, it is crucial to find novel approaches to increase their discovery rate. Radiomics is an emerging field that seeks to uncover and quantify the concealed information present in biomedical images by utilising machine or deep learning approaches. The extracted features can be integrated into predictive models, as numerous reports have emphasised their usefulness in the staging of lung cancer. However, there is a paucity of studies examining the detection of OLMs using quantitative features derived from images. Hence, the objective of this review was to investigate the potential application of PET- and/or CT-derived quantitative radiomic features for the identification of OLMs.

FDG PET Hybrid Imaging

Molecular imaging with positron emission tomography (PET) using tumour-seeking radiopharmaceuticals has gained wide acceptance in oncology with many clinical applications. The hybrid imaging modality PET/CT (computed tomography) allows assessing molecular as well as morphologic information at the same time. Therefore, PET/CT represents an efficient tool for whole-body staging and re-staging within one imaging modality. In oncology, the glucose analogue 18-F-fluorodeoxyglucose (FDG) is the most widely used PET/CT radiopharmaceutical in clinical routine. FDG PET and FDG PET/CT have been used for staging and re-staging of tumour patients in numerous studies. This chapter will discuss the use and the main indications of FDG PET/CT in oncology with special emphasis on lung cancer, lymphoma, head and neck cancer, melanoma and breast cancer (among other tumour entities). A review of the current literature is given with respect to primary diagnosis, staging and diagnosis of recurrent disease. Besides its integral role in diagnosis, staging and re-staging of disease in oncology, there is increasing evidence that FDG PET/CT can be used for therapy response assessment (possibly influencing therapeutic management and treatment planning) by evaluating tumour control, which will also be discussed in this chapter.

Focal fluorine-18 fluorodeoxyglucose-avid parotid findings in patients with lung cancer: prevalence and characteristics

OBJECTIVE

Correct interpretation of incidental tumors is important to plan an appropriate treatment. We assessed the incidence and imaging characteristics of fluorine-18 fluorodeoxyglucose (F-FDG)-avid focal parotid findings (FPFs) in patients with lung cancer.

PATIENTS AND METHODS

FPFs in PET-computed tomography reports of cancer patients were searched. Those with known parotid malignancies, lymphoma, and diffuse F-FDG uptake in the entire parotid gland were not included in the analysis.

RESULTS

FPFs were detected in 38/3120 cancer patients (1.23%), observed as a soft tissue mass with a mean diameter 1.6±0.5 cm (range 0.8-2.7 cm) and a mean maximum standardized uptake value of 7.7±3.7 (range 2.5-17.8). FPFs were observed in 23/604 (3.8%) patients with lung cancer, compared with 6/1366 (0.4%) with breast cancer and 5/842 (0.6%) with gastrointestinal malignancies. We assessed FPFs appearances in 23 patients with lung cancer (18 men, mean age 72.8±9.2); 20 (87%) were current or past smokers. There was no correlation between the stage or histopathological type of the lung cancer and the prevalence of parotid lesions. In four patients with histopathology, no malignancy was detected. For an additional 11 patients with available imaging and clinical follow-up (mean follow-up 15.5±13.5 months, range 3-42 months), FPFs were consistent with benign lesions.

CONCLUSION

FPFs were more prevalent among patients with lung cancer than in patients with other malignancies. As F-FDG avidity was moderate to high, FPFs may mimic distant metastases. It is important to consider FPFs in the interpretation of a focal parotid lesion as misinterpretation may result in denial of appropriate therapy.