PET/CT in therapy evaluation of patients with lung cancer

Abstract

FDG-PET/CT is a well documented and widespread used imaging modality for the diagnosis and staging of patient with lung cancer. FDG-PET/CT is increasingly used for the assessment of treatment effects during and after chemotherapy. However, PET is not an accepted surrogate end-point for assessment of response rate in clinical trials. The aim of this review is to present current evidence on the use of PET in response evaluation of patients with lung cancer and to introduce the pearls and pitfalls of the PET-technology relating to response assessment. Based on this and relating to validation criteria, including stable technology, standardization, reproducibility and broad availability, the review discusses why, despite numerous studies on response assessment indicating a possible role for FDG-PET/CT, PET still has no place in guidelines relating to response evaluation in lung cancer.

Keywords::

• chemotherapy
• EGFR TKI
• FDG-PET/CT
• FLT
• non-small cell lung cancer
• PERCIST
• prognosis
• small cell lung cancer
• therapy
• treatment response

Financial and competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• The value of 2-[¹⁸F]fluoro-2-deoxy-D-glucose (FDG)-PET for monitoring treatment response is impeded by the diversity and heterogeneity of the published data.

• Qualitative measurements from FDG-PET contains prognostic information but is only significantly associated with survival when combined with information on volume, that is tumor lesion glycolysis and metabolic tumor volume.

• Variations in body composition and injected dose, differences in scanner hardware and reconstruction are sources of variation with great impact on generated standardized uptake value.

• Based on reproducibility studies of FDG uptake in untreated tumors, relative changes ≥20% are unlikely to be caused by measurement errors or variations in tumor metabolic activity.

• A significant contribution from FDG-PET during and after treatment is the detection of new foci and thus progressive disease.

• Applying the the European Organization for Research and Treatment of Cancer or PET Response Criteria in Solid Tumors (PERCIST) criteria for metabolic response can predict response early in the course of chemotherapy and is associated to progression-free survival; however, less so in the neoadjuvant setting.

• After neoadjuvant chemoradiotherapy, PET can predict histopathological response in the primary tumor but is not sufficiently sensitive or specific as a stand-alone test for mediastinal restaging.

• Based on current evidence, FDG-PET is promising for early evaluation during EGFR TKI treatment, but there is no basis for recommending 18F-flourothymidine-PET instead of FDG-PET.

• FDG-PET/computed tomography (CT) has an established role in the staging process of small cell lung cancer, but in therapy evaluation, FDG-PET/CT has not shown superiority to CT.

• PERCIST holds the potential to create consensus and comparability in the acquisition and interpretation of data, whereas the European Organization for Research and Treatment of Cancer criteria, in their current form, can be applied in too many different ways to fulfill the target about standardization. More widespread dissemination of PERCIST 1.0 is needed.

Notes

FDG: 2-[¹⁸F]fluoro-2-deoxy-D-glucose; NSCLC: Non-small-cell lung cancer; SUV: Standardized uptake value.

Data taken from [79].