¹⁸F-FDG PET-CT In Non-small Cell Lung Cancer: Relationship Between Primary Tumor FDG Uptake With Extensional And Metastatic Potentials

ObjectiveLung cancer, one of the high morbidity and mortality of malignant tumors, is thefrequent reason caused cancer related death, which has an increasing incidence andmortality in recent years worldwide. Depending on biological behavior, lung cancer isdivided into small cell lung cancer (SCLC) and non-small cell lung caner (NSCLC).85%of total lung cancer patients are non-small cell lung caner patients. And about30%-40%patients are too late to be on operation or intolerant of operation whendiagnosed. Therefore in patients with non-small cell lung caner, early diagnosis andaccurate staging are very important in decision making for treatment and predictingoutcome. However, a marked heterogeneity exists between patients, even those withthe same performance status, and between tumors, despite being of the same stage andpathological type.18F-fluorodeoxyglucose positron emission tomography–computedtomography (18F-FDG PET-CT), which provides morphological and metabolic data ofmalignancy, has become an important non-invasive tool for the staging as well as forthe assessment of the primary tumor and distant metastasis in non-small cell lungcaner. FDG uptake in the primary tumor measured as the maximum standardizeduptake value (SUVmax) by PET, which well known measure indicating the disease activity or the aggressiveness of tumor, can be easily obtained and is the most widelyused parameter for the analysis of18F-FDG PET images in clinical practice. Thepurpose of the present study was to explore the relationships between primary tumorFDG uptake measured as the SUVmax and local extension, and nodal or distant organmetastasis in patients with non-small cell lung caner on pretreatment18F-FDGPET-CT. At the same time, we attempted to evaluate the relationship between tumorsize, primary tumor stages, nodal stages, and overall stages of the patients and theirprimary tumor SUVmax in order to further analysis the prognostic value of theprimary tumor SUVmax in non-small cell lung caner patients.MethodsThere is a retrospective study of ninety-three patients with non-small cell lungcaner who underwent18F-FDG PET-CT scans before the initiation of treatment inShandong Cancer Hospital and Institute from June2008and May2011. All patientswere defined by histopathological evidences. Primary tumor SUVmax was calculated;tumor size, stages, presence of local extension, lymph node and distant organmetastases were recorded. The patients with SUVmax≥2.5were divided into low andhigh SUVmax groups by using the median primary tumor SUVmax. The lowSUVmax group (group A) consisted of45patients with SUVmax less than10.5, thehigh SUVmax group (group B) consisted of46patients with SUVmax≥10.5. Theirdata were compared statistically. Data processing is performed using SPSS17.0medical statistical analysis and P values less than0.05were considered significant.ResultsA final total of91cases with SUVmax≥2.5were included for analysis. Theaverage SUVmax was6.94±2.01and14.51±3.96in the low and high SUV groups,respectively. In the low SUV group,19patients (42.2%) had a local extension,22(48.9%) had mediastinal and/or hilar lymph node metastasis, and9had distant organmetastasis (20.0%). In the high SUV group,31patients (67.4%) had a local extension,37(80.4%) had mediastinal and/or hilar lymph node metastasis, and18(39.1%) had distant organ metastases. There was a significant difference in local extension rate (P=0.016), distant organ metastasis rate (P=0.046), and most significant difference inlymph node metastasis rate (P=0.002) between the two groups. The mean SUVmaxin patients without any metastasis (n=27,29.7%) was7.42±2.91and this wassignificantly lower than the mean SUVmax (12.18±4.94) in patients with lymph nodeand/or distant organ metastasis (n=64,70.3%),(P﹤0.01). In addition, there was amoderate correlation between primary tumor SUVmax and tumor size (r=0.642, P﹤0.01), tumor stages (r=0.546, P﹤0.01), node stages(r=0.388, P﹤0.01), andoverall stage (r=0.445, P﹤0.01).ConclusionsThis study has shown that the patients of non-small cell lung caner with highSUVmax present significantly more frequent local extension and nodal or distantorgan metastasis than patients with low SUVmax. Patients with non-small cell lungcaner having high SUVmax might be candidate for more aggressive or moreindividualized treatment to achieve better disease control. Furthermore, they mayneed a close follow-up because of their higher extensional and metastatic potentials.