Comparison of 2D planar and 3D volumetric methods for estimation of split renal function by ^99mTc-DMSA scintigraphy.

© 2022 Associazione Italiana di Fisica Medica e SanitariaPurpose: Split renal function (SRF) can be measured by using several methods in 99mTc-DMSA scintigraphy. Geometric mean (GM) based methods derived from planar images(2D) have been used for several years, besides; 3D-methods were also reported as an option for assessment of SRF. The purpose of this study to compare 2D and 3D methods for calculation of SRF in pediatric and adult patients. Methods: We evaluated 212 patients, underwent both planar and SPECT 99mTc-DMSA scintigraphy.2D-SRFs were calculated by GM without background correction (SRFnobcg), GM with background correction in crescent formation from lower lateral borders (SRFcres), and GM with background correction in circumferential formation, including the whole kidney surroundings (SRFcirc). In 3D settings, SRF was measured with SPECT (SRFspect). Paired t-test was used to compare the mean SRFs of each group. Bland-Altman method was used as an agreement method for each method. Analyses were performed based on left kidney SRFs. Results: In comparison of 2D and 3D methods, SRFspect was significantly different from SRFnobcg and SRFcres (p=<0.001) but not from SRFcirc (p = 0.155) in all patients. Similar results were found for patients with high creatinine level, SRFcirc and SRFspect were not significantly different (p = 0.317), while significant differences were found between SRFspect and SRFnobcg/SRFcres (p=<0.001).On the other hand, all 2D-methods showed statistical differences (p=<0.001–0.026) from 3D-method in pediatric patients. Bland-Altman-plot demonstrated that SRFcirc underestimated the poor functioning kidneys. Conclusion: SRFcirc can be used in measurement of SRF in adult patients with normal functioning kidneys in busy clinics. However, SRFspect provides more accurate results and suggested particularly for pediatric patients and poor functioning kidneys

Safety of Fibroblast Activation Protein-Targeted Radionuclide Therapy by a Low-Dose Dosimetric Approach Using 177Lu-FAPI04.

Objectives This study is set out to estimate the radiation-absorbed doses to normal organs and tumor tissue using low-dose Lu-177-FAPI04 dosimetry to determine the safety and theranostic potential of fibroblast activation protein-targeted radionuclide therapy. Patients and Methods Four patients with metastatic advanced-stage cancer were administered low-dose Lu-177-FAPI04 for dosimetry measurements. Data acquisition for dosimetry of normal organs and tumors was performed by whole-body and 3D SPECT/CT imaging at 4, 24, 48, and 96 hours after administering Lu-177-FAPI04. Blood samples were drawn at 5, 15, 30, 60, 60, 120, and 180 minutes, and at 24, 48, and 96 hours for bone marrow dosimetry calculations. Results Mean absorbed doses per megabecquerel were 0.25 +/- 0.16 mGy (range, 0.11-0.47 mGy), 0.11 +/- 0.08 mGy (range, 0.06-0.22 mGy), and 0.04 +/- 0.002 mGy (range, 0.04-0.046 mGy) for kidneys, liver, and bone marrow, respectively. The respective maximum estimated amount of radioactivity to reach radiation-absorbed dose limits were 120.9 +/- 68.6 GBq, 47.5 +/- 2.8 GBq, 397.8 +/- 217.1 GBq, and 52.4 +/- 15.3 GBq for kidneys, bone marrow, liver, and total body. The mean absorbed dose per megabecquerel was 0.62 +/- 0.55 mGy for bone metastases, 0.38 +/- 0.22 mGy for metastatic lymph nodes, 0.33 +/- 0.21 mGy for liver metastases, and 0.37 +/- 0.29 for metastatic soft tissue. The maximum absorbed dose in a tumor lesion was 1.67 mGy/MBq for bone, 0.6 mGy/MBq for lymph node, 0.62 mGy/MBq for liver, and 1 mGy/MBq for soft tissue. Conclusions The mean absorbed dose to organs at risk with Lu-177-FAPI04 is reasonably low, allowing for low tumor-absorbed dose rates by administering a higher dose. Further research on optimizing therapeutic efficacy and using alternative radioisotopes is necessary, along with an individualized dosimetric approach

Can PSMA-based tumor burden predict response to docetaxel treatment in metastatic castration-resistant prostate cancer?

Purpose We investigated the role of PSMA-derived tumor burden in predicting docetaxel (DTX) therapy response in metastatic castration-resistant prostate cancer (mCRPC). Methods Fifty-two mCRPC patients who received at least six cycles of DTX as the first-line treatment following Ga-68-PSMA PET/CT were enrolled in this retrospective study. Total PSMA-derived tumor volume (TV-PSMA) and total lesion PSMA activity (TL-PSMA) were derived from metastatic lesions. A >= 50% decline in PSA was defined as a response; a >= 25% increase in PSA was defined as progression. Univariate/multivariate logistic and cox regression analyses were performed to predict PSA response, OS, and TTP. Results Twelve (23%) patients had PSA progression after chemotherapy, while 40 patients (77%) achieved a PSA response. On univariate analysis, a significant association was found between TV-PSMA (p = 0.001), TL-PSMA (p = 0.001), pre-PSA (p = 0.012), LDH (p = 0.003), Hg (p = 0.035), and PSA response to DTX. High TV-PSMA (> 107 cm(3)) (p = 0.04) and high LDH (> 234 U/L) (p = 0.017) were 8.2 times and 12.2 times more likely for DTX failure in multivariate regression analyses. The median TTP was 16 months, and the median OS was not reached. Patients with high TV-PSMA (p = 0.017), high TL-PSMA (> 1013 cm(3)) (p = 0.042), high age (> 70 years) (p = 0.016), and high LDH (p <= 0.001) had significantly shorter OS, while only high TV-PSMA (p = 0.038) and high age (p = 0.006) were significantly related with shorter TTP. High TV-PSMA (p = 0.017) and high age (p = 0.01) were significant predictors for shorter OS, while only high age (p = 0.006) was a significant predictor for shorter TTP in multivariate analysis. Conclusion Patients with high TV-PSMA had a significantly higher risk for DTX failure. PSMA-based tumor burden prior to DTX therapy seems to be a reliable predictive tool for survival in mCRPC patients

Prognostic significance of ⁶⁸Ga-Pentixafor PET/CT in multiple myeloma recurrence: a comparison to ¹⁸F-FDG PET/CT and laboratory results.

Purpose This study investigates the prognostic value of Ga-68-Pentixafor PET/CT using PET-derived quantitative in multiple myeloma (MM) patients with suspected recurrence in comparison to F-18-FDG PET/CT and clinical data. Methods Twenty-four MM patients with suspicion for relapse who underwent Ga-68-Pentixafor and F-18-FDG PET/CT were retrospectively evaluated. Total bone marrow glycolysis for F-18-FDG (TBMFDG) and total bone marrow uptake for Ga-68-Pentixafor PET/CT (TBMCXCR4) were calculated using whole-body metabolic tumor burden obtained by dedicated software (MIM 7.0.6). The patients were followed for 19-24 months, and the association of PET-derived quantitative data with overall survival (OS) was analyzed. Results Ga-68-Pentixafor PET/CT was positive in 17 patients, of which 13 were also positive on F-18-FDG PET/CT, whereas 7 patients were negative on both scans. The positive rate of Ga-68-Pentixafor and F-18-FDG PET/CT on a patient-based approach was 70.8% and 54.1%, respectively. Ga-68-Pentixafor positivity was significantly associated with OS (p = 0.009), and F-18-FDG positivity was at the margin of statistical significance (p = 0.056). TBMCXCR4 and TBMFDG were negatively correlated with OS (r = -0.457, p = 0.025 and r = -0.617, p = 0.001, respectively). The OS was negatively correlated with beta-2-microglobulin levels (r = -0.511, p = 0.01) and CRAB score (r = -0.592, p = 0.002) as an indicator of the end-organ disease, which confirmed these results. Serum beta-2-microglobulin levels and CRAB score were also correlated with TBMCXCR4 (r = 0.442, p = 0.039 and r = 0.573, p = 0.003, respectively) and TBMFDG (r = 0.543, p = 0.009 and r = -0.424, p = 0.003, respectively). Conclusion Ga-68-Pentixafor PET/CT positivity is a negative prognostic factor in the survival outcome of MM patients. Complementary Ga-68-Pentixafor PET/CT has the potential to overcome F-18-FDG PET/CT limitations and helps a more precise risk stratification