Mark A. Green

Purpose of Review: This review will explore the latest in advanced imaging techniques, with a focus on the complementary nature of multiparametric, multimodality imaging using magnetic resonance imaging (MRI) and positron emission tomography (PET). Recent Findings: Advanced MRI techniques including perfusion-weighted imaging (PWI), MR spectroscopy (MRS), diffusion-weighted imaging (DWI), and MR chemical exchange saturation transfer (CEST) offer significant advantages over conventional MR imaging when evaluating tumor extent, predicting grade, and assessing treatment response. PET performed in addition to advanced MRI provides complementary information regarding tumor metabolic properties, particularly when performed simultaneously. ¹⁸F-fluoroethyltyrosine (FET) PET improves the specificity of tumor diagnosis and evaluation of post-treatment changes. Incorporation of radiogenomics and machine learning methods further improve advanced imaging. Summary: The complementary nature of combining advanced imaging techniques across modalities for brain tumor imaging and incorporating technologies such as radiogenomics has the potential to reshape the landscape in neuro-oncology.

Purpose This study was undertaken to evaluate radiation dosimetry for the prostate-specific membrane antigen targeted [⁶⁸Ga]Ga-P16-093 radiopharmaceutical, and to initially assess agent performance in positron emission tomography (PET) detection of the site of disease in prostate cancer patients presenting with biochemical recurrence. Procedures Under IND 133,222 and an IRB-approved research protocol, we evaluated the biodistribution and pharmacokinetics of [⁶⁸Ga]Ga-P16-093 with serial PET imaging following intravenous administration to ten prostate cancer patients with biochemical recurrence. The recruited subjects were all patients in whom a recent [⁶⁸Ga]Ga-PSMA-11 PET/X-ray computed tomography (CT) exam had been independently performed under IND 131,806 to assist in decision-making with regard to their clinical care. Voided urine was collected from each subject at ~ 60 min and ~ 140 min post-[⁶⁸Ga]Ga-P16-093 injection and assayed for Ga-68 content. Following image segmentation to extract tissue time-activity curves and corresponding cumulated activity values, radiation dosimetry estimates were calculated using IDAC Dose 2.1. The prior [⁶⁸Ga]Ga-PSMA-11 PET/CT exam (whole-body PET imaging at 60 min post-injection, performed with contrast-enhanced diagnostic CT) served as a reference scan for comparison to the [⁶⁸Ga]Ga-P16-093 findings. Results [⁶⁸Ga]Ga-P16-093 PET images at 60 min post-injection provided diagnostic information that appeared equivalent to the subject’s prior [⁶⁸Ga]Ga-PSMA-11 scan. With both radiopharmaceuticals, sites of tumor recurrence were found in eight of the ten patients, identifying 16 lesions. The site of recurrence was not detected with either agent for the other two subjects. Bladder activity was consistently lower with [⁶⁸Ga]Ga-P16-093 than [⁶⁸Ga]Ga-PSMA-11. The kidneys, spleen, salivary glands, and liver receive the highest radiation exposure from [⁶⁸Ga]Ga-P16-093, with estimated doses of 1.7 × 10⁻¹, 6.7 × 10⁻², 6.5 × 10⁻², and 5.6 × 10⁻² mGy/MBq, respectively. The corresponding effective dose from [⁶⁸Ga]Ga-P16-093 is 2.3 × 10⁻² mSv/MBq. Conclusions [⁶⁸Ga]Ga-P16-093 provided diagnostic information that appeared equivalent to [⁶⁸Ga]Ga-PSMA-11 in this limited series of ten prostate cancer patients presenting with biochemical recurrence, with the kidneys found to be the critical organ. Diminished tracer appearance in the urine represents a potential advantage of [⁶⁸Ga]Ga-P16-093 over [⁶⁸Ga]Ga-PSMA-11 for detection of lesions in the pelvis.

300 Background: Detection of advanced prostate cancer has historically relied on radionuclide bone scanning and cross-sectional imaging with varying degrees of sensitivity and specificity based on the clinical scenario. In the current era, use of NaF and Choline based whole body scans have led to increased detection, but access to these scan can be limited and expense can be prohibitive. Similar to choline based scanning, acetate is metabolically active in cancer, including prostate. Methods: Fifty-six men previously diagnosed with prostate cancer with PSA recurrences after some failed primary treatment, have undergone whole body C-11 Acetate PET scans at Indiana University since June of 2013. Patient demographics, prior treatments, PSA values, prior imaging, post-scan therapies, and therapeutic outcomes have been recorded prospectively and updated as follow-up information becomes available. Results: Analysis of these initial 56 men demonstrated 31/56 men had a C-11 Acetate PET scan that lead to further definitive loco-regional treatments, including salvage radiation therapy ( 12), salvage regional lymph node dissection (11) and salvage cryo-ablation (8), while 9/56 men had initiation of hormonal ablation, secondary to detection of systemic disease. The remainder of these men had negative scans and are currently under continued active surveillance without evidence of disease progression requiring either loco-regional or systemic therapy. Closer analysis of the 31 men who received loco-regional treatments revealed 10 men who benefited with clear PSA declines, 4 men who failed to demonstrate a benefit from the definitive loco-regional therapy and 17 of men are too early to determine at the time of analysis. Careful pathological analysis of the regional lymph dissections revealed the limit of detection of the C-11 Acetate PET scan of greater than or equal to 3mm. Correlations of SUV readings of detected prostate cancer lesions with PSA kinetics, suggest importance of both PSA doubling time and absolute PSA value cutoffs. Conclusions: The C-11 Acetate PET scan is a useful adjunct to current imagining techniques and provides additional clinical information to guide clinicians caring for prostate cancer patients.