AIM: To examine the role of [18F]FDG PET/CT for assessing response to immunotherapy in patients with some solid tumors. METHODS: Data recorded in a multicenter (n = 17), retrospective database between March and November 2021 were analyzed. The sample included patients with a confirmed diagnosis of a solid tumor who underwent serial [18F]FDG PET/CT (before and after one or more cycles of immunotherapy), who were >18 years of age, and had a follow-up of at least 12 months after their first PET/CT scan. Patients enrolled in clinical trials or without a confirmed diagnosis of cancer were excluded. The authors classified cases as having a complete or partial metabolic response to immunotherapy, or stable or progressive metabolic disease, based on a visual and semiquantitative analysis according to the EORTC criteria. Clinical response to immunotherapy was assessed at much the same time points as the serial PET scans, and both the obtained responses were compared. RESULTS: The study concerned 311 patients (median age: 67; range: 31–89 years) in all. The most common neoplasm was lung cancer (56.9%), followed by malignant melanoma (32.5%). Nivolumab was administered in 46.3%, and pembrolizumab in 40.5% of patients. Baseline PET and a first PET scan performed at a median 3 months after starting immunotherapy were available for all 311 patients, while subsequent PET scans were obtained after a median 6, 12, 16, and 21 months for 199 (64%), 102 (33%), 46 (15%), and 23 (7%) patients, respectively. Clinical response to therapy was recorded at around the same time points after starting immunotherapy for 252 (81%), 173 (56%), 85 (27%), 40 (13%), and 22 (7%) patients, respectively. After a median 18 (1–137) months, 113 (36.3%) patients had died. On Kaplan–Meier analysis, metabolic responders on the first two serial PET scans showed a better prognosis than non-responders, while clinical response became prognostically informative from the second assessment after starting immunotherapy onwards. CONCLUSIONS: [18F]FDG PET/CT could have a role in the assessment of response to immunotherapy in patients with some solid tumors. It can provide prognostic information and thus contribute to a patient’s appropriate treatment. Prospective randomized controlled trials are mandatory.

Background: Undifferentiated soft-tissue sarcomas (USTS) are one of the most common sarcoma histotypes in adults. The standard of care is surgical excision plus adjuvant radiotherapy, while the use of perioperative chemotherapy is still controversial. The aim of this study was to investigate the value of pre-treatment [18F]FDG PET/CT conventional metrics and textural features in predicting disease-free survival (DFS) and overall survival (OS) in patients with USTS of the limbs and trunk. Methods: [18F]FDG PET/CT scans of 51 consecutive patients with locally advanced USTS were retrospectively evaluated. Conventional and textural PET parameters were analysed and tested as predictive factors for DFS and OS. Results: During a median follow up of 50.7 months, 23 (45.1%) and 29 (56.9%) patients had death or disease progression, respectively. Univariate analysis revealed a significant association for perioperative treatment, PET volumetric parameters and the textural feature GLCM_correlation with DFS and OS. In multivariate analysis, perioperative treatment and GLCM_correlation were the only independent factors, allowing stratification of the population into three different prognostic classes. Conclusion: GLCM_correlation can identify USTS at high risk of relapse and death, thus helping to optimize the perioperative treatment of patients.

At a time of increasing evidence for dose-effect relationships in radioembolization (RE) with ⁹⁰Y-microspheres, the general consensus is that there is an urgent need for accurate treatment planning and dose assessment in patients undergoing RE treatment. This work aimed at assessing the usefulness of ^99mTc macroaggregated albumin (MAA) SPECT/CT imaging for personalized provisional RE dosimetry considering a 3D-printed patientlike phantom (AdboMan phantom). A homemade tool was developed in MATLAB for image analysis and absorbed dose calculation. Two dose calculaton methods were implemented and used to calculate dose volume histograms: (I) dose kernel method and (II) local energy deposition method. The accuracy of the two different dosimetric methods was evaluated by means of 3D $\gamma$-index (1%–1 mm and 2%–2 mm) implemented in the tool. Differences between the two dose calculation methods using the 3D $\gamma$-index are within 1%–1 mm and 2%–2 mm for all AbdoMan inserts, with a passing rate of 99.9% and 100%, respectively, proving a good agreement between the two calculation methods. The present study supports the use of ^99mTc-MAA SPECT acquisition for provisional dosimetry along with the local energy deposition method to convert reconstructed SPECT data into absorbed dose maps. As long as ^99mTc-MAA SPECT acquisitions are performed on liver lesions larger than 40 mm, the absorbed dose computed by means of the local energy deposition method can lead to results in line with those obtained by Monte Carlo calculations.

Background/Objectives: To evaluate the efficacy of balloon occlusion trans-arterial hepatic radioembolization with Yttrium-90 (b-TARE) in optimizing dose activity in patients with large or multifocal Hepatocellular Carcinoma (HCC) lesions with heterogeneous macroaggregate distribution by retrospectively comparing outcomes with a similar cohort treated with standard TARE. Methods: This single-center restrospective study included sixty-three consecutive patients with unresectable HCC treated with TARE, of whom 24/63 had balloon-occluded TARE and 39/63 had standard TARE. Both cohorts included large or multifocal HCC lesions characterized by heterogeneous macroaggregate distribution, also in relation to the angiosome framework. The impact of b-TARE was analyzed using 2D and 3D dosimetry with dedicated software on post-procedural SPECT-CT. Dosimetric b-TARE results were retrospectively compared with standard TARE. Results: Both 2D and 3D SPECT-CT analyses demonstrated a better dosimetry profile in the b-TARE group. Concerning 2D evaluation, the activity intensity peak was significantly higher in the b-TARE group compared to the TARE group (998.6 ± 394.9 vs. 578.8 ± 313.3, p = 0.004). Regarding 3D dose analysis, the mean intra-lesion dose administered was significantly higher in the b-TARE group (162.7 ± 54.3 Gy vs. 111.2 ± 44.5 Gy, p = 0.01). There was no increase in significant complications or in the mean dose delivered to the normal liver in the b-TARE group. Conclusions: The employment of balloon occlusion in TARE was associated with a higher activity intensity peak and lesion absorbed dose on voxel-based dosimetry, compared to standard TARE, in patients with heterogeneous HCC and uneven macroaggregate distribution, without increasing mean non-tumoral liver dose.