Quantitative analysis of glucose consumption measured by maximum standardized uptake value (SUVmax) in lung adenocarcinoma (LA) remains in discussion and metabolic information provided by FDG-PET is not included in cancer staging
Lung cancer is the leading cause of cancer-related mortality worldwide and lung adenocarcinoma (LA) is the most frequently diagnosed subtype. Nowadays TNM stage is the strongest prognostic factor of LA and the main tool to tailor treatment.
Traditionally LA staging has been mainly based on morphological criteria, although it is well known the importance of metabolic aspects in the cancer process.
18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) has been included in the evaluation of lung cancer patients because of the key role of this technique in the detection of nodal and distance metastases.
Researchers performed a retrospective analysis of 112 patients with histologically-confirmed LA in whom a whole-body. 18F-FDG PET/CT scanning was performed preoperatively between 2008 and 2014. Disease stage was based on 7th edition of the American Joint Committee on Cancer tumor, node, metastasis (TNM), staging manual.
The clinical TNM stage was determined based on physical examination, CT scan, 18F-FDG PET/CT, bronchoscopy and/or CT-guided biopsy and in some cases by means of mediastinoscopy.
In situ subtype was not included in the stage and the survival analysis. Patients with clinical stage IIIB and IV were excluded from the study. Patients were followed for cancer recurrence and survival for a minimum of 16 months after surgery. Information was obtained by reviewing the medical records of all patients.
Imaging protocol of 18F-FDG PET scans
18F-FDG PET/CT was performed using an integrated PET-CT scanner. Patients were fasted for a minimum of 6 h prior to the procedure. Patients with blood glucose concentrations exceeding 160 mg/mL before radiotracer injection were excluded from the analysis.
Images were obtained from base of the skull to mid-thigh level, 60 min after intravenous administration of 5.29 MBq/kg (0.14 mCi/kg).
Comparisons between SUVmax and histologic subtypes were performed with Kruskal-Wallis followed by a Dunn’s test. Overall (OS) and disease-free survival (DFS) was calculated.
SUVmax was histologically-dependent (P<0.001): AIS 0.5±0.1, MIA 1.1±0.9 lepidic 3.3±3.1, acinar 8.6±6.7, papillary 3.9±5.1, micropapillary 4.9±3.4, solid 10.4±5.4 and invasive mucinous 2.7±1.2. SUVmax was associated with the TNM stage in stage IA and IB. SUVmax was significantly lower in patients with K-RAS and EGFR mutation
Lung adenocarcinoma represents a heterogeneous disease with different metabolic profiles and different behaviors in the different subtypes. Quantitative analysis by SUVmax 18F-FDG PET offers an approach to the glucose consumption in the primary lesion, providing information with a prognostic value that improves the treatment planning in each particular LA case.
Consequently, the quantitative analysis of glucose consumption by the tumor cell, measured by SUVmax, can be a criterion to be considered in the presurgical evaluation of these patients. Maybe metabolic profile of tumor cells should be incorporated into future LA staging together with other criteria.