Efficacy of early imaging with 68Ga-PSMA-I&T in the discrimination of pelvic lesions in prostate cancer patients.

Abstract

Abstract Objective 68Ga-PSMA-uptake shows accumulation in the malignant lesions of prostate cancer patients as early as 5\xa0min p.i. Studies indicate the value of adding an early image of the pelvis to the imaging protocol of 68Ga-PSMA-11 PET/CT scan showed contradictory results. In this study we planned to assess the significance of an additional early imaging in 68Ga-PSMA I&T PET/CT imaging in prostate cancer patients. Materials and methods A total of 35 prostate cancer patients referred to 68Ga-PSMA-I&T PET/CT imaging for restaging of the disease due to suspicion of relapse of the after definitive therapy were enrolled. First an early static pelvis image was obtained at a maximum of 300\xa0s following injection of the radiotracer. Sixty minutes post injection a whole-body PET/CT scan was conducted with an emission time of 3\xa0min per bed position. The lesions which were categorized as local recurrence, bone lesion and lymph node metastasis in the early images, were compared with the late images in terms of number of lesions detected and SUVmax values. Results 68Ga-PSMA-I&T PET/CT was positive in 23 of 35 patients (65.7%). A pathological uptake was observed in the prostatic bed site, in the pelvic lymph nodes, and in the bones in 17 patients (48.5%), 12 patients (34.2%), and 13 patients (37.1%), respectively. In one patient, focal pathological increased uptake in the prostatic bed with a SUVmax value of 5.8 was detected but this lesion disappeared in the late images (Fig. 1). The average SUVmax values of the lesions in the prostatic bed were 13.7\xa0±\xa012.1 versus 26.3\xa0±\xa023.8 in the 5\xa0min and 60\xa0min studies respectively (p\xa0 Conclusion Our study is the first in the literature to evaluate the impact of adding an early static pelvic image to the 68GaPSMA-I&T scan, in the detection rate of the lesions. Although there was no marked discordance between the two sets of images, the addition of an early image to the imaging protocol of 68GaPSMA-I&T scan would increase the efficacy of detection of malignant lesions in the pelvis, which might show rapid clearance and has the risk of being masked by the urinary system activity.