68Ga-Pentixafor PET/CT demonstrating higher CXCR4 density in small cell lung carcinoma than in non-small cell variant

Excerpt

An over-expression of chemokine receptor subtype CXCR4 in many human cancers and targeting CXCR4/CXCR12-axis is viewed as a promising approach for developing specific PET imaging probes [1, 2]. Recently, the pre-clinical evaluation and clinical validation of ⁶⁸Ga-labeled Pentixafor (a cyclic pentapeptide) for PET imaging of CXCR4 expression have been described [3‐5]. We present a MIP image (A) of ⁶⁸Ga-Pentixafor PET/CT in a NSCLC patient showing an intense tracer uptake (transaxial- B; SUV_max = 8.8) in the right lung, mediastinal/supra-clavicular lymph nodes, brain (C; SUV_max = 2.2) and L4 spine (D; SUV_max = 4.8). FACS analysis from the lung mass demonstrated significant CXCR4 receptor density with maximum fluorescence intensity- (MFI) of 120 (E). Interestingly, an intense uptake (MIP-F; transaxial image- H, SUV_max = 13.2) of ⁶⁸Ga-Pentixafor as compared to that of ¹⁸F-FDG (MIP-G; axial-I; SUV_max = 8.0) was observed in a SCLC patient. SCLC in terms of high CXCR4 expression is known to behave more aggressively, and the higher uptake (SUV_max = 13.2) of 68Ga-Pentixafor in this patient was associated with significantly higher CXCR4 expression (MFI = 142.0) than in NSCLC (MFI = 120; SUV_max = 8.8) patient. This image highlights that 68Ga-Pentixafor PET/CT provides an accurate in-vivo localization of CXCR4 expression which can be used for disease assessment and patient selection for appropriate CXCR4 inhibitor therapies.

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