Safety and survival outcomes in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) treated with lutetium-177–prostate-specific membrane antigen (177Lu-PSMA) after radium-223 (223Ra): Interim analysis of the RALU study

5040

Background: 223Ra and 177Lu-PSMA both prolong overall survival (OS) in different mCRPC settings. Previous data from the observational REASSURE (Sartor O, et al. 2021) and WARMTH (Ahmadzadehfar H, et al. 2021) studies suggested the feasibility of sequencing 223Ra and 177Lu-PSMA therapies. Here we used data from the observational, retrospective RALU study to further examine the safety and clinical outcomes of sequential 223Ra/177Lu-PSMA therapy in pts with mCRPC. Methods: This interim analysis investigated the baseline characteristics, safety (primary endpoint) and OS (secondary endpoint) in pts who received 177Lu-PSMA after 223Ra using retrospective data collected in German centers. Results: Data from 49 pts were available for this interim analysis. At baseline, before the start of 177Lu-PSMA, 73% of pts were Eastern Cooperative Oncology Group performance status (ECOG PS) 1 and 27% ECOG PS 2. Visceral metastases were present in 31% of pts. Median prostate-specific antigen (PSA) and alkaline phosphatase (ALP) were 287 ng/ml and 142 U/L, respectively (Table). 70% of pts received ≥4 life-prolonging therapies prior to 177Lu-PSMA, with abiraterone acetate (80%), enzalutamide (67%) and docetaxel (92%) being the most frequently used. 74% of pts received ≥5 223Ra injections. Pts received either PSMA-617 (67%) or PSMA I&T (33%): 65% of pts received 1–4 cycles and 33% received 5–6 cycles. Median duration of 177Lu-PSMA therapy was 4.9 months (m) (0–57.1). Median time from the last 223Ra dose to first 177Lu-PSMA dose was 9.3 m (0.9–41.9). Any grade treatment-emergent adverse events (TEAEs) from the start of 177Lu-PSMA therapy to 30 days of follow-up occurred in 91.8% of pts, and serious TEAEs in 20% of pts. Grade 3-4 hematologic laboratory abnormalities up to 90 days post-177Lu-PSMA occurred in 34.7% of pts for anemia, 12.8% for thrombocytopenia and 2.0% for neutropenia. No grade 5 toxicities occurred. 39% of pts had ≥30% decline in PSA during 177Lu-PSMA treatment. Median OS was 12.6 m (95% CI 8.8–16.1) from the start of 177Lu-PSMA therapy. Conclusions: In this real-world retrospective analysis of selected pts with advanced mCRPC, the 223Ra/177Lu-PSMA treatment sequence was clinically feasible and well tolerated. [Table: see text]

A Role for PET/CT in response assessment of malignant pleural mesothelioma

Malignant pleural mesothelioma is a rare type of cancer, whose incidence, however, is increasing and will presumably continue to rise in the coming years. Key features of this disease comprise its mantle-shaped, pleura-associated, often multifocal growth, which cause diagnostic challenges. A growing number of mesotheliomas are being treated with novel immunotherapies for which no image derived general response criteria have been established. However, recent studies indicate that FDG-PET/CT could be superior for response assessment compared to CT-based criteria. This article aims at providing an overview of response assessment criteria dedicated to malignant pleural mesothelioma, such as mRECIST, iRECIST, and PERCIST. In addition, the potential future role of PET/CT in the management of malignant pleural mesothelioma will also be discussed.

Effects of anti-TNF-therapy on inflammatory, structural and osteoblastic activity lesions in radiographic axial spondyloarthritis - a prospective proof-of-concept study using PET/MRI of SIJ and spine

OBJECTIVES

Proof-of-concept trial on the effect of TNF-inhibitors on osteoblastic activity by Na[¹⁸ F]F-PET/MRI in relation to inflammatory and structural lesions in r-axSpA patients during 6 months of treatment.

METHODS

Clinically active r-axSpA patients (n=16) were prospectively included to undergo Na[¹⁸ F]F-PET/MRI of the SIJ and spine (n=10) at baseline and follow-up. Three readers (1 for PET/MRI, 2 for conventional MRI) evaluated all images, blinded to timepoint. Bone marrow edema (BME), structural lesions (fat lesions (FL), sclerosis, erosions and ankylosis) and Na[¹⁸ F]F uptake were recorded on the level of SIJ (SIJ-Q) and vertebral corners (VC).

RESULTS

Overall, 11 male and 5 female patients (mean age 38.6±12.0 years) were followed-up for a mean of 4.6 (range 3-6) months. A total of 128 SIJ-Q and 920 VCs were analysed at each timepoint. At baseline, Na[¹⁸ F]F uptake was found in 96.0% SIJ-Qs with BME, 94.2% with sclerosis and 88.3% with FL. At follow-up, 65.3% of SIJ-Q with BME (p<0.001), 33.8% with sclerosis (p=0.23) and 24.5% with FL (p=0.01) showed decrease of Na[¹⁸ F]F uptake. For VCs, Na[¹⁸ F]F uptake was found in 81.5% edges with sclerosis, 41.9% with FL and 33.7% with BME at baseline. At follow-up, 73.5% VC with BME (p=0.01), 53.3% with FL (p=0.03) and 55.6% with sclerosis (p=0.16) showed decrease in Na[¹⁸ F]F uptake.

CONCLUSION

Anti-TNF treatment led to significant decrease of osteoblastic activity within 3-6 months, especially but not solely at sites with inflammation. Larger datasets are needed for confirmation of the anti-osteoblastic effects of TNF-inhibitors for prevention of radiographic progression in axSpA.

[Prostate-specific membrane antigen positron emission tomography (PSMA PET) for urologists-when and which tracer?]

BACKGROUND

Prostate-specific membrane antigen positron emission tomography (PSMA PET) is increasingly replacing conventional imaging for staging of prostate cancer. A major challenge is its appropriate use and correct interpretation.

OBJECTIVES

How and when is PSMA PET used in patient care to optimally direct therapy?

MATERIALS AND METHODS

Systematic presentation and discussion of the current state of knowledge, guidelines and expert knowledge on PSMA PET with a summary of ongoing studies.

CONCLUSION

PSMA PET is the new standard for systemic staging of prostate cancer, enabling precision patient care with novel local, oligometastatic, and systemic treatment approaches.

Free-breathing 3D Stack of Stars GRE (StarVIBE) sequence for detecting pulmonary nodules in 18F-FDG PET/MRI

BACKGROUND

The free-breathing T1-weighted 3D Stack of Stars GRE (StarVIBE) MR sequence potentially reduces artifacts in chest MRI. The purpose of this study was to evaluate StarVIBE for the detection of pulmonary nodules in ¹⁸F-FDG PET/MRI.

MATERIAL AND METHODS

In this retrospective analysis, conducted on a prospective clinical trial cohort, 88 consecutive women with newly diagnosed breast cancer underwent both contrast-enhanced whole-body ¹⁸F-FDG PET/MRI and computed tomography (CT). Patients' chests were examined on CT as well as on StarVIBE and conventional T1-weighted VIBE and T2-weighted HASTE MR sequences, with CT serving as the reference standard. Presence, size, and location of all detectable lung nodules were assessed. Wilcoxon test was applied to compare nodule features and Pearson's, and Spearman's correlation coefficients were calculated.

RESULTS

Out of 65 lung nodules detected in 36 patients with CT (3.7 ± 1.4 mm), StarVIBE was able to detect 31 (47.7%), VIBE 26 (40%) and HASTE 11 (16.8%), respectively. Overall, CT showed a significantly higher detectability than all MRI sequences combined (65 vs. 36, difference 44.6%, p < 0.001). The VIBE showed a significantly better detection rate than the HASTE (23.1%, p = 0.001). Detection rates between StarVIBE and VIBE did not significantly differ (7.7%, p = 0.27), but the StarVIBE showed a significant advantage detecting centrally located pulmonary nodules (66.7% vs. 16.7%, p = 0.031). There was a strong correlation in nodule size between CT and MRI sequences (HASTE: ρ = 0.80, p = 0.003; VIBE: ρ = 0.77, p < 0.001; StarVIBE: ρ = 0.78, p < 0.001). Mean image quality was rated as good to excellent for CT and MRI sequences.

CONCLUSION

The overall lung nodule detection rate of StarVIBE was slightly, but not significantly, higher than conventional T1w VIBE and significantly higher than T2w HASTE. Detectability of centrally located nodules is better with StarVIBE than with VIBE. Nevertheless, all MRI analyses demonstrated considerably lower detection rates for small lung nodules, when compared to CT.

Tumor Sink Effect in 68Ga-PSMA-11 PET: Myth or Reality?

We aimed to systematically determine the impact of tumor burden on ⁶⁸Ga-prostate-specific membrane antigen-11 (⁶⁸Ga-PSMA) PET biodistribution by the use of quantitative measurements. Methods: This international multicenter, retrospective analysis included 406 men with prostate cancer who underwent ⁶⁸Ga-PSMA PET/CT. Of these, 356 had positive findings and were stratified by quintiles into a very low (quintile 1, ≤25 cm³), low (quintile 2, 25-189 cm³), moderate (quintile 3, 189-532 cm³), high (quintile 4, 532-1,355 cm³), or very high (quintile 5, ≥1,355 cm³) total PSMA-positive tumor volume (PSMA-VOL). PSMA-VOL was obtained by semiautomatic segmentation of total tumor lesions using qPSMA software. Fifty prostate cancer patients with no PSMA-positive lesions (negative scan) served as a control group. Normal organs, which included salivary glands, liver, spleen, and kidneys, were semiautomatically segmented using ⁶⁸Ga-PSMA PET images, and SUV_mean was obtained. Correlations between the SUV_mean of normal organs and PSMA-VOL as continuous and categoric variables by quintiles were evaluated. Results: The median PSMA-VOL was 302 cm³ (interquartile range [IQR], 47-1,076 cm³). The median SUV_mean of salivary glands, kidneys, liver, and spleen was 10.0 (IQR, 7.7-11.8), 26.0 (IQR, 20.0-33.4), 3.7 (IQR, 3.0-4.7), and 5.3 (IQR, 4.0-7.2), respectively. PSMA-VOL showed a moderate negative correlation with the SUV_mean of the salivary glands (r = -0.44, P < 0.001), kidneys (r = -0.34, P < 0.001), and liver (r = -0.30, P < 0.001) and a weak negative correlation with the spleen SUV_mean (r = -0.16, P = 0.002). Patients with a very high PSMA-VOL (quintile 5, ≥1,355 cm³) had a significantly lower PSMA uptake in the salivary glands, kidneys, liver, and spleen than did the control group, with an average difference of -38.1%, -40.0%, -43.2%, and -34.9%, respectively (P < 0.001). Conclusion: Tumor sequestration affects ⁶⁸Ga-PSMA biodistribution in normal organs. Patients with a very high tumor load showed a significantly lower uptake of ⁶⁸Ga-PSMA in normal organs, confirming a tumor sink effect. As similar effects might occur with PSMA-targeted radioligand therapy, these patients might benefit from increased therapeutic activity without exceeding the radiation dose limit for organs at risk.

PSMA PET Validates Higher Rates of Metastatic Disease for European Association of Urology Biochemical Recurrence Risk Groups: An International Multicenter Study

The European Association of Urology (EAU) prostate cancer guidelines panel recommends risk groups for biochemical recurrence (BCR) of prostate cancer to identify men at high risk of progression or metastatic disease. The rapidly growing availability of PSMA-directed PET imaging will impact prostate cancer staging. We determined the rates of local and metastatic disease in BCR and biochemical persistence (BCP) of prostate cancer stratified by EAU BCR risk groups and BCP. Methods: Patients with BCR or BCP were enrolled under the same prospective clinical trial protocol conducted at 3 sites (n = 1,777 [91%]: UCLA, n = 662 [NCT02940262]; University of California San Francisco, n = 508 [NCT03353740]; University of Michigan, n = 607 [NCT03396874]); 183 patients with BCP from the Universities of Essen, Bologna, and Munich were included retrospectively. Patients with BCR had to have sufficient data to determine the EAU risk score. Multivariate, binomial logistic regression models were applied to assess independent predictors of M1 disease. Results: In total, 1,960 patients were included. Post–radical prostatectomy EAU BCR low-risk, EAU BCR high-risk, and BCP groups yielded distant metastatic (M1) detection in 43 of 176 (24%), 342 of 931 (37%), and 154 of 386 (40%) patients. For postradiotherapy EAU BCR low-risk and EAU BCR high-risk groups, the M1 detection rate was 113 of 309 (37%) and 110 of 158 (70%), respectively. BCP, high-risk BCR, and higher levels of serum prostate-specific antigen were significantly associated with PSMA PET M1 disease in multivariate regression analysis. PSMA PET revealed no disease in 25% and locoregional-only disease in 33% of patients with post–radical prostatectomy or postradiotherapy EAU BCR high risk. Conclusion: Our findings support the new EAU classification; EAU BCR high-risk groups have higher rates of metastatic disease on PSMA PET than do the low-risk groups. Discordant subgroups, including metastatic disease in low-risk patients and no disease in high-risk patients, warrant inclusion of PSMA PET stage to refine risk assessment.

Pitfalls and common findings in 68Ga-FAPI-PET - A pictorial analysis

Introduction: Fibroblast activation protein inhibitor positron emission tomography (FAPI-PET) is a new tool in the diagnostic workup of cancer. With growing volume of applications pitfalls and common findings need to be considered for Ga-68-FAPI-PET image interpretation. The aim of this study was to summarize common findings and report pitfalls in Ga-68-FAPI-PET. Methods and materials: 91 patients underwent whole-body PET/CT with either FAPI-04 (N = 25) or FAPI-46 (N = 66). Findings were rated in a consensus session of two experienced readers. Pitfalls and common findings were defined as focal or localized uptake above background and categorized as unspecific / non-malignant and grouped into degenerative, muscular, scarring / wound-healing, uterine, mammary glands and head-and-neck findings. Frequency of findings was reported on a per-patient and per-group basis and SUV_max, SUVmean and SUVpeak was measured. Results: Non-tumor specific tracer uptake was found in 81.3 % of patients. The most frequent finding was tracer uptake in degenerative lesions (51.6%) with mean SUV_max 7.7 ± 2.9 and head-and-neck (45.1%) findings. Except for salivary glands, the uptake values did not differ between 10 and 60 min p.i. in most findings. Uterine uptake was found in most women (66.7%) with mean SUV_max 12.2 ± 7.3 and uptake correlated negatively with age (SUV_max r = -0.6, p<0.01; SUVpeak r = -0.57, p<0.01; SUVmean r = -0.58, p<0.01). Conclusion: Pitfalls include non-tumor specific Ga-68-FAPI uptake in degenerative lesions, muscle, head-and-neck, scarring, mammary glands or uterus. Here we summarize findings to inform readers at centers introducing Ga-68-FAPI-PET to avoid common mistakes.

Visualization of Fibroblast Activation After Myocardial Infarction Using 68Ga-FAPI PET

AIMS

The aim of this retrospective analysis was to examine the pattern of cardiac 68Ga-fibroblast-activation protein-α inhibitor (FAPI) uptake in patients after acute myocardial infarction (AMI) using PET and to investigate its association with results of coronary angiography. We correlated FAPI uptake with biomarkers of myocardial damage including left ventricular function.

METHODS AND RESULTS

A cohort of 10 patients with no history of coronary artery disease underwent PET 18 ± 20.6 days after AMI (ST-segment elevation myocardial infarction [n = 5] and non-ST-segment elevation infarction [n = 5]), respectively. SUVmax, SUVmean, and SUVpeak of localized tracer uptake were calculated; tracer uptake volume was reported as fibroblast activation volume (FAV), with imaging data being correlated with clinical parameters. Focal FAPI uptake was observed in all patients. Average uptake at 10 minutes postinjection was 8.9 ± 4.4 (SUVmax), 7.6 ± 4.0 (SUVpeak), and 5.3 ± 2.8 (SUVmean), respectively. Affected myocardium showed a partial to complete match between tracer uptake and confirmed culprit lesion by coronary angiography in 44.4% and 55.6% of patients, respectively. A strong correlation between FAV and peak creatine kinase level (r = 0.90, P < 0.01) and inverse correlation of FAV with left ventricular function (r = -0.69, P < 0.05) was observed.

CONCLUSIONS

This analysis demonstrates in vivo visualization of fibroblast activation after AMI. The uptake area showed a very good agreement with the affected coronary territory. A strong correlation of the de novo established parameter FAV with left ventricular function and peak creatine kinase was observed. This imaging modality may provide important insights into mechanisms of structural remodeling after AMI at an early stage.

Prospective phase 2 trial of PSMA-targeted molecular RadiothErapy with 177Lu-PSMA-617 for metastatic castration-reSISTant Prostate Cancer (RESIST-PC): efficacy results of the UCLA cohort

The objective of this study was to determine prospectively the efficacy profile of 2 activity regimens of ¹⁷⁷Lu-PSMA therapy in patients with progressive metastatic castrate-resistant prostate cancer (mCRPC): 6.0 vs. 7.4 GBq. Methods: RESIST-PC (NCT03042312) was a prospective multicenter phase 2 trial. Patients with progressive mCRPC after ≥ 1 novel androgen-axis drug, either chemotherapy naïve or postchemotherapy, with sufficient bone marrow reserve, normal kidney function, and sufficient PSMA expression by PSMA PET were eligible. Patients were randomized (1:1) into 2 activity groups (6.0 or 7.4 GBq) and received up to 4 cycles every 8 wk. The primary endpoint was the efficacy of ¹⁷⁷Lu-PSMA measured by the prostate-specific antigen (PSA) response rate (RR) after 2 cycles (≥50% decline from baseline). Secondary endpoints included the PSA RR (≥50% decline) at any time (best response), and overall survival (OS). Results: The study was closed at enrollment of 71/200 planned patients because of sponsorship transfer. We report here the efficacy of the University of California Los Angeles cohort results only (n = 43). The PSA RRs after 2 cycles and at any time were 11/40 (28%, 95% CI 15-44), 6/13 (46%, 95% CI 19-75), and 5/27 (19%, 95% CI 6-38), and 16/43 (37%, 95% CI 23-53), 7/14 (50%, 95% CI 23-77), and 9/29 (31%, 95% CI 15-51) in the whole cohort, the 6.0-GBq group, and the 7.4-GBq group, respectively (P = 0.12 and P = 0.31). The median OS was 14.0 mo (95% CI 10.1-17.9), 15.8 (95% CI 11.8-19.4), and 13.5 (95% CI 10.0-17.0) in the whole cohort, the 6.0-GBq group, and the 7.4 GBq group, respectively (P = 0.87). OS was longer in patients who experienced a PSA decline ≥ 50% at any time than in those who did not: median, 20.8 versus 10.8 mo (P = 0.005). Conclusion: In this prospective phase 2 trial of ¹⁷⁷Lu-PSMA for mCRPC, the median OS was 14 mo. Despite the heterogeneous study population and the premature study termination, the efficacy profile of ¹⁷⁷Lu-PSMA appeared to be favorable and comparable with both activity regimens (6.0 vs. 7.4 GBq). Results justify confirmation with real-world data matched-pair analysis and further clinical trials to refine and optimize the ¹⁷⁷Lu-PSMA therapy administration scheme to improve tumor radiation dose delivery and efficacy.

Diagnostic performance of [124I]m-iodobenzylguanidine PET/CT in patients with pheochromocytoma

^123/131I-MIBG scintigraphy has shown a high specificity for imaging pheochromocytoma and paraganglioma however with low sensitivity due to low spatial resolution. ¹²⁴I-MIBG PET may overcome this limitation to improve the staging of patients with (suspected) pheochromocytoma. Methods: We analyzed the sensitivity, specificity, positive and negative predictive values (PPV, NPV) of ¹²⁴I-MIBG PET in 43 consecutive patients with suspected (recurrence of) pheochromocytoma using histopathological (n = 25) and clinical validation (n = 18) as standard of truth. Furthermore, we compared ¹²⁴I-MIBG PET versus contrast enhanced CT (CE-CT) per-patient and per-lesion detection rate of ¹²⁴I-MIBG PET in 13 additional patients with known metastatic malignant pheochromocytoma (MMP). Results: ¹²⁴I-MIBG PET/CT was positive in 19/43 (44%) patients with suspected pheochromocytoma. Presence of pheochromocytoma was confirmed in 22/43 (51%). ¹²⁴I-MIBG PET/CT sensitivity, specificity, PPV, NPV were 86%, 100%, 100%, 88%, respectively. ¹²⁴I-MIBG PET was positive in 11/13 (85%) MMP patients. Combined ¹²⁴I-MIBG PET and CE-CT detected 173 lesions, of which 166 (96%) and 118 (68%) were visible on ¹²⁴I-MIBG PET and CE-CT, respectively. Discussion: ¹²⁴I-MIBG PET detects pheochromocytoma with high accuracy at initial staging and high detection rate at re-staging. Superior diagnostic performance aids guidance of surgical and medical management including personalized ¹³¹I-MIBG therapy.

Diagnostic Accuracy of 68Ga-PSMA-11 PET for Pelvic Nodal Metastasis Detection Prior to Radical Prostatectomy and Pelvic Lymph Node Dissection: A Multicenter Prospective Phase 3 Imaging Trial

Importance

The presence of pelvic nodal metastases at radical prostatectomy is associated with biochemical recurrence after prostatectomy.

Objective

To assess the accuracy of prostate-specific membrane antigen (PSMA) 68Ga-PSMA-11 positron emission tomographic (PET) imaging for the detection of pelvic nodal metastases compared with histopathology at time of radical prostatectomy and pelvic lymph node dissection.

Design, Setting, and Participants

This investigator-initiated prospective multicenter single-arm open-label phase 3 imaging trial of diagnostic efficacy enrolled 764 patients with intermediate- to high-risk prostate cancer considered for prostatectomy at University of California, San Francisco and University of California, Los Angeles from December 2015 to December 2019. Data analysis took place from October 2018 to July 2021.

Interventions

Imaging scan with 3 to 7 mCi of 68Ga-PSMA-11 PET.

Main Outcomes and Measures

The primary end point was the sensitivity and specificity for the detection pelvic lymph nodes compared with histopathology on a per-patient basis using nodal region correlation. Each scan was read centrally by 3 blinded independent central readers, and a majority rule was used for analysis.

Results

A total of 764 men (median [interquartile range] age, 69 [63-73] years) underwent 1 68Ga-PSMA-11 PET imaging scan for primary staging, and 277 of 764 (36%) subsequently underwent prostatectomy with lymph node dissection (efficacy analysis cohort). Based on pathology reports, 75 of 277 patients (27%) had pelvic nodal metastasis. Results of 68Ga-PSMA-11 PET were positive in 40 of 277 (14%), 2 of 277 (1%), and 7 of 277 (3%) of patients for pelvic nodal, extrapelvic nodal, and bone metastatic disease. Sensitivity, specificity, positive predictive value, and negative predictive value for pelvic nodal metastases were 0.40 (95% CI, 0.34-0.46), 0.95 (95% CI, 0.92-0.97), 0.75 (95% CI, 0.70-0.80), and 0.81 (95% CI, 0.76-0.85), respectively. Of the 764 patients, 487 (64%) did not undergo prostatectomy, of which 108 were lost to follow-up. Patients with follow-up instead underwent radiotherapy (262 of 379 [69%]), systemic therapy (82 of 379 [22%]), surveillance (16 of 379 [4%]), or other treatments (19 of 379 [5%]).

Conclusions and Relevance

This phase 3 diagnostic efficacy trial found that in men with intermediate- to high-risk prostate cancer who underwent radical prostatectomy and lymph node dissection, the sensitivity and specificity of 68Ga-PSMA-11 PET were 0.40 and 0.95, respectively. This academic collaboration is the largest known to date and formed the foundation of a New Drug Application for 68Ga-PSMA-11.

Trial Registration

ClinicalTrials.gov Identifiers: NCT03368547, NCT02611882, and NCT02919111.

68Ga-PSMA-11 PET/CT Improves Tumor Detection and Impacts Management in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the third most frequent cause of cancer-related death. A growing number of local and systemic therapies are available, and accurate staging is critical for management decisions. We assessed the impact of neovasculature imaging by ⁶⁸Ga-PSMA-11 PET/CT on disease staging, prognostic groups, and management of patients with HCC compared with staging with CT. Methods: Forty patients who received imaging with ⁶⁸Ga-PSMA-11 PET/CT for HCC staging between September 2018 and September 2019 were retrospectively included. Management before and after PET scanning was assessed by standardized surveys. The presence of HCC was evaluated by 3 masked readers on a per-patient and per-region basis for PET/CT (PET criteria) and multiphase contrast-enhanced CT (CT criteria) in separate sessions. Lesions were validated by follow-up imaging or histopathology, and progression-free survival was recorded. Endpoints were detection rate and positive predictive value for ⁶⁸Ga-PSMA-11 PET versus CT, interreader reproducibility, and changes in stage, prognostic groups, and management plans. Results: Median age was 65 y (range, 37-81 y), and median Child-Pugh score was 5 (range, 5-9). Most patients were treatment-naïve (27/40, 67.5%). The sensitivity of PET versus CT to identify liver lesions for patients with lesion validation was 31 of 32 (97%) for both modalities, whereas it was 6 of 6 (100%) versus 4 of 6 (67%), respectively, for extrahepatic lesions. PET and CT each had a positive predictive value of 100% at the liver level. PET versus CT stage was congruent in 30 of 40 (75%) patients; upstaging was seen in 8 of 40 patients (20%), whereas 2 of 40 (5%) had downstaging by PET. Intended management changed in 19 of 40 patients (47.5%); 9 of 19 of these patients were found to have detectable distant metastases (47.4%) and assigned stage 4 disease, most of whom were shifted to systemic therapy (8/9, 89%). Two patients underwent ¹⁷⁷Lu-PSMA-617 radioligand therapy. Median progression-free survival was 5.2 mo for the entire cohort; 5.3 mo for PET M0, and 4.7 mo for PET M1 patients, respectively. Conclusion: ⁶⁸Ga-PSMA-11 PET demonstrated higher accuracy than CT in the detection of HCC metastases and was associated with a management change in about half the patient cohort.

Repeatability of 68Ga-PSMA-HBED-CC PET/CT-derived total molecular tumor volume

Background: Molecular tumor volume (MTV) is a parameter of interest in advanced prostate cancer for assessing total disease burden on prostate specific membrane antigen (PSMA) PET. Although software segmentation tools can delineate whole-body MTV, a necessary step towards meaningful monitoring of total tumor burden and treatment response through PET is establishing the repeatability of these metrics. The present study assesses the repeatability of total MTV and related metrics for ⁶⁸Ga-PSMA-HBED-CC in advanced prostate cancer. Methods: Eighteen patients from a prior repeatability study who underwent two test-retest PSMA PET/CT scans within a mean interval of 5 days were reanalyzed. Within subject coefficient of variation and repeatability coefficients (RC) were analyzed on a per lesion and per patient basis. For the per lesion analysis, individual lesions were segmented for analysis by a single reader. For per patient analysis, subgroups of up to 10 lesions (single reader) and the total tumor volume per patient were segmented (independently by two readers). Image parameters were: MTV; maximum, peak, and mean standardized uptake value; total lesion PSMA and the related metric PSMA quotient (which is integrating lesion volume and PSMA avidity). Results: In total, 192 segmentations were analyzed for the per lesion analysis and 1662 segmentations for the total tumor volume per patient analysis (combining the 2 readers and 2 scans). The RC of the MTV of single lesions was 77% (95%CI:63-96%). The RC improved after aggregation of up to 10 manually selected lesions into subgroups assessed per patient, 33% (95%CI:25-46%). The RC of the semi-automatic MTVtotal was 35% (95%CI:25-50. Alternating readers between scans led to a comparable RC of 37% (95%CI:28-49%) for MTVtotal meaning that the metric is robust between scanning sessions and between readers. Conclusion: ⁶⁸Ga-PSMA-HBED-CC PET-derived semi-automatic MTVtotal is repeatable and reader independent with a change of ±35% representing a true change in tumor volume. Volumetry of single manually selected lesions has considerably lower repeatability, and volumetry based on subgroups of these lesions, while showing acceptable repeatability, is less systematic. The semi-automatic analysis of MTVtotal employed in this study offers an efficient and robust means of assessing response to therapy.

Analysis of risk factors and prognosis in differentiated thyroid cancer with focus on minimal extrathyroidal extension

AIMS

In contrast to all prior AJCC/TNM classifications for differentiated thyroid cancer (DTC) the 8th edition does not take minimal extrathyroidal extension (M-ETE) into consideration for local tumor staging. We therefore aimed to retrospectively assess the specific impact of M-ETE on the outcome of M-ETE patients treated in our clinic.

METHODS

DTC patients with M-ETE and a follow-up time of ≥ 5 years were included and matched with an identical number of patients without M-ETE, but with equal histopathological tumor subtype and size. The frequency of initially metastatic disease among groups was compared using Fisher's exact test, the recurrence rate by virtue of log-rank test. Fisher's exact test and multivariate analysis were used to account for the presence of confounding risk factors.

RESULTS

One hundred sixty patients (80 matching pairs) were eligible. With other confounding risk factors being equal, the prevalence of N1-/M1-disease at initial diagnosis was comparable among groups (M-ETE: 42.5 %; no M-ETE: 32.5 %; p = 0.25). No differences with regard to the recurrence rate were shown. However, M-ETE patients were treated with external beam radiation therapy more often (16.3 % vs. 1.3 %; p = 0.004) and received higher median cumulative activities of ¹³¹I (10.0 vs. 8.0 GBq; p < 0.001).

DISCUSSION

Although having played a pivotal role for local tumor staging of DTC for decades M-ETE did not increase the risk for metastases at initial diagnosis and the recurrence rate in our cohort. Patients with M-ETE had undergone intensified treatment, which entails a possible confounding factor that warrants further investigation in randomized controlled trials.

N-staging in large cell neuroendocrine carcinoma of the lung: diagnostic value of [18F]FDG PET/CT compared to the histopathology reference standard

Background

Large cell neuroendocrine carcinoma of the lung (LCNEC) is a rare entity occurring in less than 4% of all lung cancers. Due to its low differentiation and high glucose transporter 1 (GLUT1) expression, LCNEC demonstrates an increased glucose turnover. Thus, PET/CT with 2-[¹⁸F]-fluoro-deoxyglucose ([¹⁸F]FDG) is suitable for LCNEC staging. Surgery with curative intent is the treatment of choice in early stage LCNEC. Prerequisite for this is correct lymph node staging. This study aimed at evaluating the diagnostic performance of [¹⁸F]FDG PET/CT validated by histopathology following surgical resection or mediastinoscopy. N-staging interrater-reliability was assessed to test for robustness of the [¹⁸F]FDG PET/CT findings.

Methods

Between 03/2014 and 12/2020, 46 patients with LCNEC were included in this single center retrospective analysis. All underwent [¹⁸F]FDG PET/CT for pre-operative staging and subsequently either surgery (n = 38) or mediastinoscopy (n = 8). Regarding the lymph node involvement, sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated for [¹⁸F]FDG PET/CT using the final histopathological N-staging (pN0 to pN3) as reference.

Results

Per patient 14 ± 7 (range 4–32) lymph nodes were resected and histologically processed. 31/46 patients had no LCNEC spread into the lymph nodes. In 8/46 patients, the final stage was pN1, in 5/46 pN2 and in 2/46 pN3. [¹⁸F]FDG PET/CT diagnosed lymph node metastasis of LCNEC with a sensitivity of 93%, a specificity of 87%, an accuracy of 89%, a PPV of 78% and a NPV of 96%. In the four false positive cases, the [¹⁸F]FDG uptake of the lymph nodes was 33 to 67% less in comparison with that of the respective LCNEC primary. Interrater-reliability was high with a strong level of agreement (κ = 0.82).

Conclusions

In LCNEC N-staging with [¹⁸F]FDG PET/CT demonstrates both high sensitivity and specificity, an excellent NPV but a slightly reduced PPV. Accordingly, preoperative invasive mediastinal staging may be omitted in cases with cN0 disease by [¹⁸F]FDG PET/CT. In [¹⁸F]FDG PET/CT cN1-cN3 stages histological confirmation is warranted, particularly in case of only moderate [¹⁸F]FDG uptake as compared to the LCNEC primary.

Safety of PSMA-targeted molecular radioligand therapy with 177Lu-PSMA-617: results from the prospective multicenter phase 2 trial RESIST-PC NCT03042312

Purpose of the study: To report the safety evaluation of ¹⁷⁷Lu-PSMA-617 derived from the cohort of 64 patients exposed to ¹⁷⁷Lu-PSMA-617 in the RESIST-PC trial NCT03042312 Methods: RESIST-PC was a prospective multicenter phase 2 trial. Patients with progressive mCRPC after ≥1 novel androgen-axis drug, either chemotherapy naïve or post-chemotherapy, with sufficient bone marrow reserve, normal kidney function, sufficient PSMA expression by PSMA PET and no visceral PSMA-negative lesions were eligible. Patients were randomized (1:1) into two activity groups (6.0 or 7.4 GBq per cycle) and received up to 4 cycles every 8 weeks. The primary safety endpoint was assessed by collecting and grading Adverse Events (AE) using the CTCAE. Patients were followed until disease progression, death, serious or intolerable AE, study termination by sponsor, patient withdrawal, lost to follow-up or 24 months after the first cycle. Results: The study was closed at enrollment of 71/200 planned patients because of sponsorship transfer. A total of 64 (90.1%) patients received at least one cycle of ¹⁷⁷Lu-PSMA-617: 28 (36%) in Arm 1 (6.0 GBq) and 41 (64%) in Arm 2 (7.4GBq). There were 10 (43.5%), 19 (46.5%) and 29 (45.3%) patients who completed 4 cycles of ¹⁷⁷Lu-PSMA-617 in the 6.0 GBq arm, 7.4 GBq arm, and overall, respectively. The most common treatment-emergent adverse events (TEAEs) of any grade in the 6.0 GBq arm, the 7.4 GBq arm and overall, were dry mouth (47.8%; 63.4%; 57.8%, respectively), fatigue (56.5%; 51.2%; 53.1%), nausea (52.2%; 43.9%; 46.9%), and diarrhea (13.0%; 31.7%; 25.0%). Frequencies of all other TEAEs were comparable among the 2 groups (within 10% difference). Serious possibly drug-related TEAEs were reported for 5 (7.8%) patients overall (none were considered as probably or definitely related to treatment): one subdural hematoma Grade 4, one anemia grade 3, one thrombocytopenia grade 4, one gastrointestinal hemorrhage grade 3, and one acute kidney injury grade 3. There were no clinically significant changes in vital signs in ECGs in the 2 treatment groups. No trend to creatinine increase, or increasing frequency of shifts from normal to abnormal over time for any hematologic parameter was noted. Conclusion: ¹⁷⁷Lu-PSMA-617 was safe and well-tolerated at 6.0 and 7.4 GBq per cycle given at 8-week intervals with side effects easily managed with standard medical support. With established safety, further clinical trials applying individualized dosimetry and testing different ¹⁷⁷Lu-PSMA-617 administration schemes (activity levels, time intervals) are needed to optimize tumor dose delivery and treatment efficacy.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Nomograms to predict outcomes after 177Lu-PSMA therapy in men with metastatic castration-resistant prostate cancer: an international, multicentre, retrospective study

BACKGROUND

Lutetium-177 (¹⁷⁷Lu) prostate-specific membrane antigen (¹⁷⁷Lu-PSMA) is a novel targeted treatment for patients with metastatic castration-resistant prostate cancer (mCRPC). Predictors of outcomes after ¹⁷⁷Lu-PSMA to enhance its clinical implementation are yet to be identified. We aimed to develop nomograms to predict outcomes after ¹⁷⁷Lu-PSMA in patients with mCRPC.

METHODS

In this multicentre, retrospective study, we screened patients with mCRPC who had received ¹⁷⁷Lu-PSMA between Dec 10, 2014, and July 19, 2019, as part of the previous phase 2 trials (NCT03042312, ACTRN12615000912583) or compassionate access programmes at six hospitals and academic centres in Germany, the USA, and Australia. Eligible patients had received intravenous 6·0-8·5 GBq ¹⁷⁷Lu-PSMA once every 6-8 weeks, for a maximum of four to six cycles, and had available baseline [⁶⁸Ga]Ga-PSMA-11 PET/CT scan, clinical data, and survival outcomes. Putative predictors included 18 pretherapeutic clinicopathological and [⁶⁸Ga]Ga-PSMA-11 PET/CT variables. Data were collected locally and centralised. Primary outcomes for the nomograms were overall survival and prostate-specific antigen (PSA)-progression-free survival. Nomograms for each outcome were computed from Cox regression models with LASSO penalty for variable selection. Model performance was measured by examining discrimination (Harrell's C-index), calibration (calibration plots), and utility (patient stratification into low-risk vs high-risk groups). Models were validated internally using bootstrapping and externally by calculating their performance on a validation cohort.

FINDINGS

Between April 23, 2019, and Jan 13, 2020, 414 patients were screened; 270 (65%) of whom were eligible and were divided into development (n=196) and validation (n=74) cohorts. The median duration of follow-up was 21·5 months (IQR 13·3-30·7). Predictors included in the nomograms were time since initial diagnosis of prostate cancer, chemotherapy status, baseline haemoglobin concentration, and [⁶⁸Ga]Ga-PSMA-11 PET/CT parameters (molecular imaging TNM classification and tumour burden). The C-index of the overall survival model was 0·71 (95% CI 0·69-0·73). Similar C-indices were achieved at internal validation (0·71 [0·69-0·73]) and external validation (0·72 [0·68-0·76]). The C-index of the PSA-progression-free survival model was 0·70 (95% CI 0·68-0·72). Similar C-indices were achieved at internal validation (0·70 [0·68-0·72]) and external validation (0·71 [0·68-0·74]). Both models were adequately calibrated and their predictions correlated with the observed outcome. Compared with high-risk patients, low-risk patients had significantly longer overall survival in the validation cohort (24·9 months [95% CI 16·8-27·3] vs 7·4 months [4·0-10·8]; p<0·0001) and PSA-progression-free survival (6·6 months [6·0-7·1] vs 2·5 months [1·2-3·8]; p=0·022).

INTERPRETATION

These externally validated nomograms that are predictive of outcomes after ¹⁷⁷Lu-PSMA in patients with mCRPC might help in clinical trial design and individual clinical decision making, particularly at institutions where ¹⁷⁷Lu-PSMA is introduced as a novel therapeutic option.

FUNDING

Prostate Cancer Foundation.

Mechanisms of Resistance to Prostate-Specific Membrane Antigen-Targeted Radioligand Therapy in a Mouse Model of Prostate Cancer

Prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) is effective against prostate cancer (PCa), but all patients relapse eventually. Poor understanding of the underlying resistance mechanisms represents a key barrier to development of more effective RLT. We investigate the proteome and phosphoproteome in a mouse model of PCa to identify signaling adaptations triggered by PSMA RLT. Methods: Therapeutic efficacy of PSMA RLT was assessed by tumor volume measurements, time to progression, and survival in C4-2 or C4-2 TP53^-/- tumor-bearing nonobese diabetic scid γ-mice. Two days after RLT, the proteome and phosphoproteome were analyzed by mass spectrometry. Results: PSMA RLT significantly improved disease control in a dose-dependent manner. Proteome and phosphoproteome datasets revealed activation of genotoxic stress response pathways, including deregulation of DNA damage/replication stress response, TP53, androgen receptor, phosphatidylinositol-3-kinase/AKT, and MYC signaling. C4-2 TP53^-/- tumors were less sensitive to PSMA RLT than were parental counterparts, supporting a role for TP53 in mediating RLT responsiveness. Conclusion: We identified signaling alterations that may mediate resistance to PSMA RLT in a PCa mouse model. Our data enable the development of rational synergistic RLT-combination therapies to improve outcomes for PCa patients.

Head-to-head intra-individual comparison of biodistribution and tumor uptake of 68Ga-FAPI and 18F-FDG PET/CT in cancer patients

Purpose

FAPI ligands (fibroblast activation protein inhibitor), a novel class of radiotracers for PET/CT imaging, demonstrated in previous studies rapid and high tumor uptake. The purpose of this study is the head-to-head intra-individual comparison of ⁶⁸Ga-FAPI versus standard-of-care ¹⁸F-FDG in PET/CT in organ biodistribution and tumor uptake in patients with various cancers.

Material and Methods

This international retrospective multicenter analysis included PET/CT data from 71 patients from 6 centers who underwent both ⁶⁸Ga-FAPI and ¹⁸F-FDG PET/CT within a median time interval of 10 days (range 1–89 days). Volumes of interest (VOIs) were manually drawn in normal organs and tumor lesions to quantify tracer uptake by SUVmax and SUVmean. Furthermore, tumor-to-background ratios (TBR) were generated (SUVmax tumor/ SUVmax organ).

Results

A total of 71 patients were studied of, which 28 were female and 43 male (median age 60). In 41 of 71 patients, the primary tumor was present. Forty-three of 71 patients exhibited 162 metastatic lesions. ⁶⁸Ga-FAPI uptake in primary tumors and metastases was comparable to ¹⁸F-FDG in most cases. The SUVmax was significantly lower for ⁶⁸Ga-FAPI than ¹⁸F-FDG in background tissues such as the brain, oral mucosa, myocardium, blood pool, liver, pancreas, and colon. Thus, ⁶⁸Ga-FAPI TBRs were significantly higher than ¹⁸F-FDG TBRs in some sites, including liver and bone metastases.

Conclusion

Quantitative tumor uptake is comparable between ⁶⁸Ga-FAPI and ¹⁸F-FDG, but lower background uptake in most normal organs results in equal or higher TBRs for ⁶⁸Ga-FAPI. Thus, ⁶⁸Ga-FAPI PET/CT may yield improved diagnostic information in various cancers and especially in tumor locations with high physiological ¹⁸F-FDG uptake.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05307-1.