An International Study on the Use of PET/CT in Radiotherapy Planning in Low and Middle Income Countries

Over the years, the incidence of lung cancer has risen in some low and middle income countries due to the rise in tobacco use. Patients commonly present with lung cancer in an advanced stage (stage III and IV) are not suitable for surgical resection, but may be considered for radiotherapy. For patients in those countries who are not suitable for surgical resection, radiotherapy offers the best chance of cure, best improvement in local cancer control, best palliation and fewest side-effects. For accurate patient selection for curative treatment and accurate staging of lung cancer, the use of fused 18F-fluorodeoxyglucose Positron Emission Tomography/ Computed Tomography (FDG PET/CT) imaging has been shown to be superior to CT alone. It has also been shown to have a significant impact when used in the radiation treatment planning process and in particular for when used for target volume delineation, where a significant reduction in interobserver variation has been noted.

In recent years, many health care institutions in low and middle income countries have established Nuclear Medicine (NM) imaging in routine clinical practice in conjunction with modern Radiation Oncology (RO) facilities. The installation of hybrid PET/CT systems in these countries permits more the increased use of PET/CT for both staging and radiotherapy planning. However the successful implementation of PET/CT for radiotherapy planning (RTP) requires a degree of expertise to safely and accurately implement this imaging technique. A recently published review by the International Atomic Energy Agency (IAEA), about current trends in NM in developing countries showed there is still lack of expertise, equipment and human resources to gain benefit from this imaging technique. In RO, difficulties in the implementation of this technique are mainly related to inadequate training of staff and lack of local expertise.

Quality assurance of the PET/CT scanners might be compromised when not performed according to accepted nuclear medicine quality assurance standards. Therefore, there is a concern that, if used without appropriate training or expertise, suboptimal image quality may result and inappropriate interpretation of the PET/CT for RTP may occur. In this study to help provide PET Quality Control will be executed to aim for a standardized PET image quality that meets the minimum requirements of European Association of Nuclear Medicine standards. Participating centers will be assisted to earn the European Association of Nuclear Medicine (EANM) Research Ltd (EARL) accreditation. The quality of the imaging can be influenced by physiological and technical factors. The Standardized Uptake Value (SUV) allows for semi quantitative evaluation in PET imaging, and is influenced by these factors. Spatial resolution affects SUV values significantly and this parameter can differ a lot between multiple centers. The EANM NEMA NU 2001/2007 2 Image Quality Phantom allows for standardization of PET imaging between centers with different scanners, using the activity coefficient recovery curve (ACRC) as a parameter for quantification of this spatial resolution.

It is already known that FDG PET/CT based RTP enables appropriate selection of patients who will benefit from curative radiation therapy. One possible cause of failure in radiotherapy is the inability to accurately define the tumor edges. In these patients there are no other possible curative salvage treatment options and the disease is incurable. It is hoped that FDG PET/CT based RTP will improve tumor volume delineation (TVD) and hence improve outcomes following curative radiotherapy. There is also clear evidence that PET/CT standardizes TVD in patients with NSCLC. However, what is not known is the impact of PET/CT based TVD on patient outcomes such as survival as distinct from the benefit of PET/CT for patient selection for curative treatment. Furthermore, the impact of a training intervention on the use of PET/CT RTP in 2-year overall survival has not been studied to the best of our knowledge.

This study will evaluate the possible impact of the use of PET/CT for TVD on 2-year overall survival in patients with stage III NSCLC referred for curative intent radiotherapy with chemotherapy in low and middle income countries, this study involves a retrospective cohort study, a training intervention, and a prospective cohort study. The training intervention will focus on standard FDG PET/CT acquisition, FDG PET/CT image quality, staging procedure for FDG PET/CT acquisition and FDG PET/CT for RTP acquisition and Tumor Volume Delineation.