Imaging PARP Upregulation with [¹²³I]I-PARPi SPECT/CT in Small Cell Neuroendocrine Carcinoma

Imaging at baseline (A), early response assessment (B), and end of therapy (C). Shown from top to bottom are transaxial PET/CT, transaxial 4-h SPECT/CT, immunohistochemistry (×20 hematoxylin and eosin staining at left, ×10 PARP staining at middle and right), maximum-intensity-projection PET, and PET/CT. Hypermetabolic lung mass is seen on PET/CT (SUV_max, 3.8) and SPECT/CT at baseline. Uptake on both modalities persists at early response assessment and at end of therapy (SUV_max, 4.5 and 4.9, respectively). Immunohistochemistry was strongly positive for PARP upregulation. Disease progression was noted on maximum-intensity projections and on PET/CT, with new lymph node metastases indicated by amber arrow above orange arrow seen on both maximum-intensity projection and PET/CT imaging (SUV_max, 4.5), adrenal gland metastases indicated by blue arrow on maximum-intensity projection images, liver metastases indicated by green arrow on both maximum-intensity projection and PET/CT images, bone metastases indicated by yellow arrow in the maximum-intensity projection images and PET/CT images (last row, third column). %IA = percentage injected activity.