Assessment of Simplified Methods for Quantification of 18F-FDHT Uptake in Patients with Metastatic Castration-Resistant Prostate Cancer.

18F-fluorodihydrotestosterone (18F-FDHT) PET/CT potentially provides a noninvasive method for assessment of androgen receptor expression in patients with metastatic castration-resistant prostate cancer (mCRPC). The objective of this study was to assess simplified methods for quantifying 18F-FDHT uptake in mCRPC patients and to assess effects of tumor perfusion on these 18F-FDHT uptake metrics. Methods: Seventeen mCRPC patients were included in this prospective observational multicenter study. Test and retest 30-min dynamic 18F-FDHT PET/CT scans with venous blood sampling were performed in 14 patients. In addition, arterial blood sampling and dynamic 15O-H2O scans were obtained in a subset of 6 patients. Several simplified methods were assessed: Patlak plots; SUV normalized to body weight (SUVBW), lean body mass (SUVLBM), whole blood (SUVWB), parent plasma activity concentration (SUVPP), area under the parent plasma curve (SUVAUC,PP), and area under the whole-blood input curve (SUVAUC,WB); and SUVBW corrected for sex hormone-binding globulin levels (SUVSHBG). Results were correlated with parameters derived from full pharmacokinetic 18F-FDHT and 15O-H2O. Finally, the repeatability of individual quantitative uptake metrics was assessed. Results: Eighty-seven 18F-FDHT-avid lesions were evaluated. 18F-FDHT uptake was best described by an irreversible 2-tissue-compartment model. Replacing the continuous metabolite-corrected arterial plasma input function with an image-derived input function in combination with venous sample data provided similar Ki results (R2 = 0.98). Patlak Ki and SUVAUC,PP showed an excellent correlation (R2 > 0.9). SUVBW showed a moderate correlation to Ki (R2 = 0.70, presumably due to fast 18F-FDHT metabolism. When calculating SUVSHBG, correlation to Ki improved (R2 = 0.88). The repeatability of full kinetic modeling parameters was inferior to that of simplified methods (repeatability coefficients > 36% vs. < 28%, respectively). 18F-FDHT uptake showed minimal blood flow dependency. Conclusion:18F-FDHT kinetics in mCRPC patients are best described by an irreversible 2-tissue-compartment model with blood volume parameter. SUVAUC,PP showed a near-perfect correlation with the irreversible 2-tissue-compartment model analysis and can be used for accurate quantification of 18F-FDHT uptake in whole-body PET/CT scans. In addition, SUVSHBG could potentially be used as an even simpler method to quantify 18F-FDHT uptake when less complex scanning protocols and accuracy are required.

Real-world healthcare costs of ipilimumab in patients with advanced cutaneous melanoma in The Netherlands.

There is limited evidence on the costs associated with ipilimumab. We investigated healthcare costs of all Dutch patients with advanced cutaneous melanoma who were treated with ipilimumab. Data were retrieved from the nation-wide Dutch Melanoma Treatment Registry. Costs were determined by applying unit costs to individual patient resource use. A total of 807 patients who were diagnosed between July 2012 and July 2015 received ipilimumab in Dutch practice. The mean (median) episode duration was 6.27 (4.61) months (computed from the start of ipilimumab until the start of a next treatment, death, or the last date of follow-up). The average total healthcare costs amounted to &OV0556;81 484, but varied widely (range: &OV0556;18 131-&OV0556;160 002). Ipilimumab was by far the most important cost driver (&OV0556;73 739). Other costs were related to hospital admissions (&OV0556;3323), hospital visits (&OV0556;1791), diagnostics and imaging (&OV0556;1505), radiotherapy (&OV0556;828), and surgery (&OV0556;297). Monthly costs for resource use other than ipilimumab were &OV0556;1997 (SD: &OV0556;2629). Treatment-naive patients (n=344) had higher total costs compared with previously-treated patients (n=463; &OV0556;85 081 vs. &OV0556;78 811). Although patients with colitis (n=106) had higher costs for resource use other than ipilimumab (&OV0556;11 426) compared with patients with other types of immune-related adverse events (n=90; &OV0556;9850) and patients with no immune-related adverse event (n=611; &OV0556;6796), they had lower total costs (&OV0556;76 075 vs. &OV0556;87 882 and &OV0556;81 480, respectively). In conclusion, this nation-wide study provides valuable insights into the healthcare costs of advanced cutaneous melanoma patients who were treated with ipilimumab in clinical practice. Most of the costs were attributable to ipilimumab, but the costs and its distribution varied considerably across subgroups.