Role of 68Ga-PSMA-HBED-CC PET/CT in Patients with Anaplastic Thyroid Carcinoma

259 Aim: Anaplastic Thyroid Cancer (ATC) is the most aggressive thyroid tumour with very poor prognosis. The tumour neovasculature could potentially serve as a target for imaging as well as therapeutic strategies. One potential target for tumour neovasculature imaging is the prostate specific membrane antigen (PSMA). Therefore, the role 68Ga-PSMA-HBED-CC PET/CT in ATC was evaluated from a theranostic perspective. Methods: Twenty-Three patients (14 female, 9 male) referred as ATC based on FNAC/HPE to our institution underwent 68Ga-PSMA PET/CT scan with 3mCi of tracer injected IV after 45-60 minutes and whole body image acquisition with iterative reconstruction was done on a 64 slice PET/CT. Any abnormal focus of uptake outside the normal biodistribution, and appearing to be a metastatic lesion on CT was considered for analysis. Mean SUVmax of primary mass, nodes, distant metastases, mediastinum and liver were calculated. Uptake was graded from 0-5 based as follows (0=No lesion; 1=no uptake; 2=equal to mediastinum; 3=more than mediastinum, less than liver; 4=equal to liver; 5=more than liver).Patients with grade 5 uptake were considered to have high PSMA expression. Overall survival of all the patients was calculated from the date of diagnosis. Results: Out of 23 patients, 3 patients were eventually diagnosed as poorly differentiated carcinoma of thyroid on histopathology. Hence, final analysis was done in 20 patients (13 female,7 male). Mean age of patients was 57.8 ± 8.8 years. Mean Karnofsky Performance Score and ECOG score were 57 ± 17.8 and 2.65 ± 0.98, respectively. Three patients were stage IVB and 17 were stage IVC. On 68Ga-PSMA scan, tracer uptake was seen in primary lesion in 18 patients (17 primary and 1 residual primary, 2 were post-operative patients with no residual mass). All the 20 patients had nodal metastasis. Lung metastasis was seen in 17/20 (85%) patients. Three out of these 17 (18%) patients also showed bone metastasis and 1/17 (6%) showed brain metastasis. Mean SUVmax of primary, node, lung lesion, liver and mediastinum was 6.72±4.6, 5.7±5.6, 2.9±1.98, 5.95 ± 3.03 and 1.54 ± 0.6, respectively. In 20 patients, 18 primary masses and 89 nodes/nodal groups were detected. All 18 primary masses and 17 out of 89 nodes had an uptake score of 4 or 5. Nine patients had uptake score of 5 in the primary/node/metastasis (7+1+1). The survival of patients showing grade 5 (high) PSMA uptake ranged from 4-15 weeks and for patients showing grade 1-4 uptake ranged from 5-14 weeks from the time of diagnosis. Conclusions: In our study, from the theranostic point of view, 9 patients (45%)showed uptake more than liver i.e high PSMA expression . However this may or may not translate into therapeutic benefit since this is a single time point estimate and tumor retention is unknown as yet. Although sample size is less, survival was similar in patients with or without high expression of PSMA.