The LUTADOSE trial: tumour dosimetry after the first administration predicts progression free survival in gastro-entero-pancreatic neuroendocrine tumours (GEP NETs) patients treated with [177Lu]Lu-DOTATATE.

PURPOSE: In Peptide Receptor Radionuclide Therapy (PRRT) with [177Lu]Lu-DOTATATE of gastro-entero-pancreatic neuroendocrine tumours (GEP NETs) a question remains open about the potential benefits of personalised dosimetry. This observational prospective study examines the association of individualized dosimetry with progression free survival (PFS) in G1-G2 GEP NETs patients following the standard [177Lu]Lu-DOTATATE therapeutic regimen. METHODS: The analysis was conducted on 42 patients administered 4 times, and on 165 lesions. Dosimetry was performed after the first and the forth cycle, with two SPECT/CT scans at day 1 and 7 after administration. Global mean Tumour absorbed Dose of each patient (GTD) was calculated after cycle 1 and 4 as the sum of lesion doses weighted by lesion mass, normalized by the global tumour mass. Cumulative GTD_TOT was calculated as the mean between cycle 1 (GTD_1) and 4 (GTD_4) multiplied by 4. Patients were followed-up for median 32.8 (range 18-45.5) months, through blood tests and contrast enhanced CT (ceCT). This study assessed the correlation between global tumour dose (GTD) and PFS longer or shorter than 24 months. After a ROC analysis, we stratified patients according to the best cut-off value for two additional statistical analyses. At last a multivariate analysis was carried out for PFS > / < 24 months. RESULTS: The median follow-up interval was 33 months, ranging from 18 to 45.5 months. The median PFS was 42 months. The progression free survival rate at 20 months was 90.5%. GTD_1 and GTD_TOT were statistically associated with PFS > / < 24 m (p = 0.026 and p = 0.03 respectively). The stratification of patients on GTD_1 lower or higher than the best cut-off value at 10.6 Gy provided significantly different median PFS of 21 months versus non reached, i.e. longer than 45.5 months (p = 0.004), with a hazard ratio of 8.6, (95% C.I.: [2 - 37]). Using GTD_TOT with the best cut-off at 43 Gy, the same PFS values were obtained as after cycle 1 (p = 0.035). At multivariate analysis, a decrease in GTD_1 and, with lower impact, a higher global tumour volume were significantly associated with PFS < 24 months. We calculated the Tumour Control Probability of obtaining PFS > 24 months as a function of GTD_1. DISCUSSION: Several statistical analyses seem to confirm that simple tumour dosimetry with 2 SPECT/CT scans after the first administration allows to predict PFS values after 4 × 7.4 GBq administrations of 177Lu[Lu]-DOTATATE in G1-G2 GEP NETs. This result qualitatively confirms recent findings by a Belgian and a French study. However, dosimetric thresholds are different. This probably comes from different cohort baseline characteristics, since the median PFS in our study (42 m) was longer than in the other studies (28 m and 31 m). CONCLUSION: Tumour dosimetry after the first administration of [177Lu]Lu-DOTATATE offers an important prognostic value in the clinical decision-making process, especially for the future as alternative emitters or administration schedule may become available.

Radioembolization of Hepatocellular Carcinoma with 90Y Glass Microspheres: No Advantage of Voxel Dosimetry with Respect to Mean Dose in Dose-Response Analysis with Two Radiological Methods.

In this confirmatory study, we tested if a calculation that included the non-uniformity of dose deposition through a voxel-based dosimetric variable Ψ was able to improve the dose-response agreement with respect to the mean absorbed dose D. We performed dosimetry with 99mTc-MAA SPECT/CT and 90Y-PET/CT in 86 patients treated 8 instead of 4 days after the reference date with 2.8 times more 90Y glass microspheres/GBq than in our previous study. The lesion-by-lesion response was assessed with the mRECIST method and with an experimental densitometric criterion. A total of 106 lesions were studied. Considering Ψ as a prognostic response marker, having no Ψ provided a significantly higher AUC than D. The correlation, t-test, and AUC values were statistically significant only with the densitometric method and only with post-therapy dosimetry. In comparison with our previous study, the dose-response correlation and AUC values were poorer (maximum r = 0.43, R2 = 0.14, maximal AUC = 0.71), and the efficacy at a high dose did not reach 100%. The expected advantages of voxel dosimetry were nullified by the correlation between any Ψ and D due to the limited image spatial resolution. The lower AUC and efficacy may be explained by the mega-clustering effect triggered by the higher number of microspheres/GBq injected on day 8.

Update on radioligand therapy with 177Lu-PSMA for metastatic castration-resistant prostate cancer: clinical aspects and survival effects.

OBJECTIVE: To give an updated overview on clinical aspects and survival effects of lutetium-177-prostate-specific membrane antigen (PSMA) (177Lu-PSMA) radioligand therapy (RLT), a novel treatment option for patients with metastatic castration-resistant prostate cancer (mCRPC). METHODS: PubMed/MEDLINE database was searched for relevant articles published up to March 2021. The search was restricted to English-language articles. RESULTS: Current evidence from the literature consistently demonstrated the efficacy, safety, and survival benefit of 177Lu-PSMA RLT in mCRPC. However, current data rely predominantly on retrospective analyses, showing heterogeneity of patient population and treatment protocols. More recently, results from the first randomized phase II study (TheraP) demonstrated that 177Lu-PMSA therapy significantly improved prostate-specific antigen response rate (66% vs 37%) and had fewer grade 3/4 adverse events when compared to cabazitaxel in patients with docetaxel-pretreated, progressive mCRPC. This review is intended to provide an updated overview of treatment protocols and responses, toxicity profile, and survival effects of 177Lu-PSMA RLT. CONCLUSIONS: 177Lu-PSMA RLT has emerged as a promising targeted treatment in mCRPC. It is currently applied in compassionate use programs and following exhaustion of approved therapies. Crucial for establishing this treatment in routine clinical management will be the results of the phase III VISION trial, which may confirm the encouraging patient outcomes reported to date.

Safety Profile of the New Harmonic Focus: Different Emissivity and Temperature Behavior Between the Active and the Inactive Blade.

Ultrasonic devices disperse less energy in the tissues. The new Harmonic Focus+ (HF+) seems to be more efficient but thermal damages have been reported. This study examined the temperature and the emissivity profile of the active and passive blades of the HF+, on a pig tissue model at different power settings. The FLIR System B series thermal imaging camera has been used on various biological pig tissues to evaluate the emissivity of the ultrasonic device. The active blade heats up faster than the passive one and the increase in power increases the speed of the temperature raising only on the active blade. Increasing the power setting reduces the dissection time and the temperature of both blades. Active blade temperatures of <60°C are obtained with cutting times close to 5 seconds; with these cutting times, the inactive blade does not exceed 30°C. The HF+ emissivity profiles demonstrate that the behavior of the inactive blade is significantly different from the active one. To prevent thermal damages, keep the active blade toward the operator, do not exceed 5 seconds of activation, use the maximum power, and avoid the use of the instrument as a dissector immediately after its activation.