The present study reviewed the current evidence for the role of 18F-fluorodeoxyglucose (FDG) PET-CT in Non-small cell lung cancer (NSCLC) diagnosis, staging, response assessment and follow up
Lung cancer is a common disease and the leading cause of cancer-related mortality, with non-small cell lung cancer (NSCLC) accounting for the majority of cases. Following the diagnosis of lung cancer, accurate staging is essential to guide clinical management and inform prognosis.
Non-small cell lung cancer (NSCLC) accounts for 75–80% of cases. In the United Kingdom, 5-year survival has been reported to be just 8%. Patients suspected or diagnosed with lung cancer are managed by a multidisciplinary team whose role is to accurately diagnose, stage and then treat patients.
The development of positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG), a radiolabelled glucose analog, has significantly impacted on the contribution of radiology to the management of this disease.
Integrated PET-CT combines the benefit of PET and CT, whilst minimizing their limitations in the diagnosis, staging, and treatment of NSCLC. PET-CT offers a superior assessment for lymph nodal involvement and for the presence of local or distant metastatic disease that can be achieved on conventional imaging alone and is often used to interpret equivocal lesions identified on such imaging modalities.
PET-CT scans can also offer predictive and prognostic information after both neoadjuvant and definitive therapy. Increasingly, the value of PET-CT in disease surveillance following treatment is being recognized and its role may increase in the future. An understanding of the limitations of FDG-PET will also provide a more accurate interpretation of the PET-CT findings.
PET-CT scans are not necessarily just performed as a one-off test and can be used to track disease over time—particularly to assess the impact of oncological therapies—i.e., chemotherapy and radiotherapy. FDG-PET offers benefit over conventional CT where although tumor shrinkage may be observed, radiation-induced inflammation and fibrosis after neoadjuvant chemotherapy or radiation therapy can make assessment difficult.
On conventional CT imaging identifying a response to treatment is simply based on a reduction in size and volume of a tumour—however, this does not necessarily correlate with clinical outcomes. PET-CT offers the opportunity to assess the level of FDG uptake and therefore tumor activity which may be a better marker.
Decreased FDG uptake as detected on PET-CT is found to correlate with improved outcomes and is a marker of effective responsiveness to the chemotherapy.
Conversely, therefore, if there is no change in activity level, this could direct a change in chemotherapeutic approach. It has been reported that evidence of high FDG uptake following the first chemotherapy cycle correlates with a poorer prognosis than patients with low FDG uptake, with the median survival of 12 months compared with 34 months.
In conclusion, the increased use of PET-CT scans in the investigation of patients with NSCLC allows for more accurate staging and therefore more appropriate management decisions. It is hoped that this translates to improved patient outcomes and increased cost-effectiveness, by avoiding inappropriate treatments.