68Ga-Pentixafor PET/CT for in-vivo mapping of CXCR4 receptors as potential radiotheranostic targets in soft tissue and bone sarcoma: preliminary results

Abstract

Objective To evaluate the diagnostic utility of 68Ga-Pentixafor PET/CT for in vivo imaging of CXCR4 receptors in soft tissue/bone sarcoma. Methods Ten (7M: 3F; mean age = 24.7 ± 14.2 years) consecutive patients with clinical and radiological evidence of bone/soft tissue sarcoma were recruited prospectively whole body 68Ga-Pentixafor PET/CT imaging was performed at 60-min after tracer administration. After performing standard CT, PET acquisition from head to toe was done (3 min/bed position) in a caudocranial direction. PET/CT data was reconstructed and SUVmax, SUVmean values, target-to-background ratio (TBR) and active tumor volume (cc) were computed for the tracer avid lesions. Histopathological and IHC analysis was performed on the surgically excised primary tumors. CXCR4 receptors’ intensity was evaluated by visual scoring. Results The mean SUVmax and SUVmean values in the primary tumors were 4.80 ± 1.0 (3.9–7.7) and 2.40 ± 0.60 (0.9–4.0). The mean TBR and tumor volume (cc) were 1.84 ± 1.3 and 312.2 ± 285. Diagnosis of osteosarcoma in 7, chondrosarcoma, leiomyosarcoma and synovial sarcoma in 1 patient each was confirmed on HP analysis. Distant metastatic lesions were seen in 3/10 patients. Nuclear CXCR4 receptors’ positivity was seen in 5, cytoplasmic in 4 and both pattern seen in 1 patient. The mean CXCR4 receptors’ intensity was found to be 7.6 ± 2. The highest SUVmax value of 7.7 was observed in the patient having both cytoplasmic and nuclear CXCR4 expression. SUVmax was found to be poorly correlated (r = 0.441) with CXCR4 expression. Conclusion 68Ga-Pentixafor PET/CT detects CXCR4 receptors over-expressed in sarcoma, its radio-theranostics potential needs detailed evaluation.