P166 Contrast enhanced PET-CT. Development and experience of a novel imaging pathway in suspected lung cancer

BackgroundNeuroimaging is recommended for stage II and III lung cancer when radical treatment is being considered. Furthermore, patients with an initial non contrast scan may require a second contrast chest CT to delineate mediastinal structures, e.g. prior to surgery. We have developed a protocol for contrast enhanced PET-CT scan, which enables a PET scan and contrast CT brain and chest to be obtained during a single examination, reducing three separate patient appointments to one. We present outcome data for the first 12 months of the pathway.MethodsPatients are selected for contrast PET-CT if at risk of stage II or III disease on initial CT– i.e., tumour >2cm/central or suspicious N1/2/3 nodes. Contrast PET-CT imaging is undertaken on a Siemens mCT Flow Edge Biograph 128 scanner; CT slice thickness 1.5mm. Initial imaging is taken from base of skull to proximal thigh 60–70 minutes post FDG tracer and 70 seconds post IV contrast. CT Brain imaging is undertaken immediately after completion of PET component of scan (~20 minutes post IV-contrast). Data was collected retrospectively for patients undergoing contrast PET-CT from June 2020 to June 2021.Results44 patients have had contrast PET-CT scans via this novel pathway. Scanning protocols were optimised until diagnostic quality images of brain and mediastinum were obtained in all patients. Final staging is summarised in table 1. 4 patients (9.1%) with stage II disease did not require further neuroimaging. One patient (2.3%) was found to have brain metastases, which were confirmed on MRI. 9 of the patients with stage III disease on PET-CT went on to have negative MRI brain imaging as per national guidelines.Abstract P166 Table 1Summary of final NSCLC staging/diagnosis for all patients who have undergone contrast enhanced PET-CT Final staging/diagnosis Number % Stage I 6 13.6 Stage IIA 2 4.5 Stage IIB 2 4.5 Stage IIIA 7 15.9 Stage IIIB 6 13.6 Stage IIIC 1 2.3 Stage IVa 6 13.6 Stage IVb 5 11.4 Carcinoid 2 4.5 Metastatic cancer 4 9.1 Non-malignant diagnosis 3 6.8 ConclusionContrast PET-CT is feasible and can provide diagnostic quality CT images of brain and mediastinum. This removes the need for a separate contrast CT brain in patients with stage II disease and enables contrast CT mediastinal images to be obtained following a low dose non contrast initial CT, eg lung cancer screening. Further work is required to assess the additional benefit/cost effectiveness of MRI brain where contrast CT-PET demonstrates sta