Biodistribution and radiation dosimetry of 124I-mIBG in adult patients with neural crest tumours and extrapolation to paediatric models

AIM

Positron emission tomography (PET) using 124I-mIBG has been established for imaging and pretherapeutic dosimetry. Here, we report the first systematic analysis of the biodistribution and radiation dosimetry of 124I-mIBG in patients with neural crest tumours and project the results to paediatric patient models.

METHODS

Adult patients with neural crest tumours who underwent sequential 124I-mIBG PET were included in this retrospective single-center analysis. PET data were acquired 4, 24, 48, and/or 120 h after administration of a mean of 43 MBq 124I-mIBG. Whole-body counting and blood sampling were performed at 2, 4, 24, 48 and 120 h after administration. Absorbed organ dose and effective dose coefficients were estimated in OLINDA/EXM 2.2 according to the MIRD formalism. Extrapolation to paediatric models was performed based on mass-fraction scaling of the organ-specific residence times. Biodistribution data for adults were also projected to 123I-mIBG and 131I-mIBG.

RESULTS

Twenty-one patients (11 females, 10 males) were evaluated. For adults, the organs exposed to the highest dose per unit administered activity were urinary bladder (1.54 ± 0.40 mGy/MBq), salivary glands (0.77 ± 0.28 mGy/MBq) and liver (0.65 ± 0.22 mGy/MBq). Mean effective dose coefficient for adults was 0.25 ± 0.04 mSv/MBq (male: 0.24 ± 0.03 mSv/MBq, female: 0.26 ± 0.06 mSv/MBq), and increased gradually to 0.29, 0.44, 0.69, 1.21, and 2.94 mSv/MBq for the 15-, 10-, 5-, 1-years-old, and newborn paediatric reference patients. Projected mean effective dose coefficients for 123I-mIBG and 131I-mIBG for adults were 0.014 ± 0.002 mSv/MBq and 0.18 ± 0.04 mSv/MBq, respectively.

CONCLUSION

PET-based derived radiation dosimetry data for 124I-mIBG from this study agreed well with historical projected data from ICRP 53. The effective dose coefficients presented here may aid in guidance for establishing weight-based activity administration protocols.

Standardized PSMA-PET Imaging of Advanced Prostate Cancer

Imaging of advanced prostate cancer is a challenging task, as it requires longitudinal characterization of disease extent in a standardized way to enable appropriate treatment selection and evaluation of treatment efficacy. In the last years, prostate-specific membrane antigen (PSMA)-PET/CT has become the reference standard examination for patients with advanced prostate cancer. Together with the rise of PSMA-PET, standardized frameworks for the reporting of image findings have been proposed, eg, the Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) and the structured reporting system for PSMA targeted PET imaging (PSMA-RADS) framework. Therefore, recent evidence on PSMA-PET derived tumor volume as useful a biomarker for outcome prognostication and related frameworks will be discussed in the article. The PROMISE framework recommends quantifying the tumor volume per-organ system, which accounts for the fact that the location of the metastases greatly influence its biological aggressiveness. In addition, changes in PSMA-PET derived tumor volume have been shown to be promising biomarkers for response assessment. Limitations of PSMA-PET will also be discussed because the tumor volume might not always be suited for response assessment. As a pitfall of PSMA-based systems, decreasing PSMA-expression might erroneously be interpreted as response to therapy. Also, especially for patients with limited disease, the tumor volume might not be ideal for response assessment. Therefore, various frameworks have been introduced to objectively measure response to therapy with PSMA-PET. Amongst these, the PSMA-PET progression (PPP) criteria and the response evaluation criteria in PSMA (RECIP) are optimized for earlier and later phenotypes of advanced prostate cancer, respectively. Variables needed to determine PPP or RECIP outcome on PSMA-PET are recorded under the umbrella of PROMISE recommendations. In this article, various reporting and response assessment frameworks are explained and discussed. Also, recent evidence for the relevance of PSMA-PET biomarkers for clinical management and outcome prognostication are shown.

Quantification performance of silicon photomultiplier-based PET for small 18F-, 68Ga- and 124I-avid lesions in the context of radionuclide therapy planning

PURPOSE

The aim of this study was to investigate conditions for reliable quantification of sub-centimeter lesions with low18F,68Ga, and124I uptake using a silicon photomultiplier-based PET/CT system.

METHODS

A small tumor phantom was investigated under challenging but clinically realistic conditions resembling prostate and thyroid cancer lymph node metastases (6 spheres with 3.7-9.7 mm in diameter, 9 different activity concentrations ranging from about 0.25-25 kBq/mL, and a signal-to-background ratio of 20). Radionuclides with different positron branching ratios and prompt gamma coincidence contributions were investigated. Maximum-, contour-, and oversize-based partial volume effect (PVE) correction approaches were applied. Detection and quantification performance were estimated, considering a ±30 % deviation between imaged-derived and true activity concentrations as acceptable. A standard and a prolonged acquisition time and two image reconstruction algorithms (time-of-flight with/without point spread function modelling) were analyzed. Clinical data were evaluated to assess agreement of PVE-correction approaches indicating lesion quantification validity.

RESULTS

The smallest 3.7-mm sphere was not visible. If the lesions were clearly observed, quantification was, except for a few cases, acceptable using contour- or oversized-based PVE-corrections. Quantification accuracy did not substantially differ between 18F, 68Ga, and 124I. No systematic differences between the analyzed reconstruction algorithms or shorter and larger acquisition times were observed. In the clinical evaluation of 20 lesions, an excellent statistical agreement between oversize- and contour-based PVE-corrections was observed.

CONCLUSIONS

At the lower end of size (<10 mm) and activity concentration ranges of lymph-node metastases, quantification with reasonable accuracy is possible for 18F, 68Ga, and 124I, possibly allowing pre-therapeutic lesion dosimetry and individualized radionuclide therapy planning.

Analysing the tumor transcriptome of prostate cancer to predict efficacy of Lu-PSMA therapy

RATIONALE

177Lu-PSMA ([177Lu]Lutetium-PSMA-617) therapy is an effective treatment option for patients with prostate specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer, but still shows a non-responder rate of approximately 30%. Combination regimes of programmed death-ligand 1 (PD-L1) inhibition and concomitant 177Lu-PSMA therapy have been proposed to increase the response rate. However, the interplay of immune landscape and 177Lu-PSMA therapy efficacy is poorly understood.

METHODS

Between March 2018 and December 2021, a total of 168 patients were referred to 177Lu-PSMA therapy in our department and received a mean total dose of 21.9 GBq (three cycles in mean). All patients received baseline PSMA positron emission tomography to assess the PSMA uptake. The histopathological specimen of the primary prostate tumor was available with sufficient RNA passing quality control steps for genomic analysis in n=23 patients. In this subset of patients, tumor RNA transcriptomic analyses assessed 74 immune-related features in total, out of which n=24 signatures were not co-correlated and investigated further for outcome prognostication.

RESULTS

In the subset of patients who received 177Lu-PSMA therapy, PD-L1 was not significantly associated with OS (HR per SD change (95% CI) 0.74 (0.42 to 1.30); SD: 0.18; p=0.29). In contrast, PD-L2 signature was positively associated with longer OS (HR per SD change 0.46 (95% CI 0.29 to 0.74); SD: 0.24; p=0.001; median OS 17.2 vs 5.7 months in higher vs lower PD-L2 patients). In addition, PD-L2 signature correlated with PSA-response (ϱ=-0.46; p=0.04). The PD-L2 signature association with OS was significantly moderated by L-Lactatdehydrogenase (LDH) levels (Cox model interaction p=0.01).

CONCLUSION

Higher PD-L2 signature might be associated with a better response to 177Lu-PSMA therapy and warrants further studies investigating additional immunotherapy. In contrast, PD-L1 was not associated with outcome. The protective effect of PD-L2 signature might be present only in men with lower LDH levels.

Conventional Imaging, MRI and 18F-FDG PET/MRI for N and M Staging in Patients with Newly Diagnosed Breast Cancer

Background: This study compares the diagnostic potential of conventional staging (computed tomography (CT), axillary sonography and bone scintigraphy), whole-body magnetic resonance imaging (MRI) and whole-body ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET/)MRI for N and M staging in newly diagnosed breast cancer. Methods: A total of 208 patients with newly diagnosed breast cancer were prospectively included in this study and underwent contrast-enhanced thoracoabdominal CT, bone scintigraphy and axillary sonography as well as contrast-enhanced whole-body ¹⁸F-FDG PET/MRI. The datasets were analyzed with respect to lesion localization and characterization. Histopathology and follow-up imaging served as the reference standard. A McNemar test was used to compare the diagnostic performance of conventional staging, MRI and ¹⁸F-FDG PET/MRI and a Wilcoxon test was used to compare differences in true positive findings for nodal staging. Results: Conventional staging determined the N stage with a sensitivity of 80.9%, a specificity of 99.2%, a PPV (positive predictive value) of 98.6% and a NPV (negative predictive value) of 87.4%. The corresponding results for MRI were 79.6%, 100%, 100% and 87.0%, and were 86.5%, 94.1%, 91.7% and 90.3% for ¹⁸F-FDG PET/MRI. ¹⁸F-FDG PET/MRI was significantly more sensitive in determining malignant lymph nodes than conventional imaging and MRI (p < 0.0001 and p = 0.0005). Furthermore, ¹⁸F-FDG PET/MRI accurately estimated the clinical lymph node stage in significantly more cases than conventional imaging and MRI (each p < 0.05). Sensitivity, specificity, PPV and NPV for the M stage in conventional staging were 83.3%, 98.5%, 76.9% and 98.9%, respectively. The corresponding results for both MRI and ¹⁸F-FDG PET/MRI were 100.0%, 98.5%, 80.0% and 100.0%. No significant differences between the imaging modalities were seen for the staging of distant metastases. Conclusions:¹⁸F-FDG PET/MRI detects lymph node metastases in significantly more patients and estimates clinical lymph node stage more accurately than conventional imaging and MRI. No significant differences were found between imaging modalities with respect to the detection of distant metastases.

Second Version of the Prostate Cancer Molecular Imaging Standardized Evaluation Framework Including Response Evaluation for Clinical Trials (PROMISE V2)

CONTEXT

Prostate-specific membrane antigen (PSMA) targeting positron emission tomography (PET) is emerging to become a reference imaging tool for the staging and restaging of patients with prostate cancer for both clinical routine and trials. The prostate cancer molecular imaging standardized evaluation (PROMISE) criteria have been proposed as a framework for whole-body staging (molecular imaging TNM staging, denoted miTNM staging) to describe the prostate cancer disease extent on PSMA-PET.

OBJECTIVE

To create a comprehensive and integrated framework for PSMA-PET image interpretation and reporting.

EVIDENCE ACQUISITION

We propose the PROMISE V2 framework, which integrates an updated miTNM system, improved assessment of local disease, and a slightly modified PSMA-expression score for clinical routine. We have added a response monitoring framework defining qualitative and quantitative parameters to be recorded for a longitudinal assessment in clinical trials.

EVIDENCE SYNTHESIS

We provide a comprehensive literature review on the current use of the PROMISE framework in clinical research and prospective trials. PROMISE variables demonstrate a clear association with survival. PSMA expression assessed by the PSMA-expression score was used in several trials, and a low PSMA-expression score is a negative prognosticator of overall survival after ¹⁷⁷Lu-PSMA radioligand therapy. The proposed imaging parameters recorded for response assessment in clinical trials can be utilized to determine response according to PSMA-PET progression (PPP) or Response Evaluation Criteria in PSMA-PET/Computed Tomography (RECIP) frameworks, but also future response criteria.

CONCLUSIONS

PROMISE V2 offers standardized reporting of disease extent for clinical routine and research. Parameters recorded within clinical trials facilitate objective response assessment.

PATIENT SUMMARY

Prostate-specific membrane antigen (PSMA) targeting positron emission tomography (PET) has become a standard imaging examination for prostate cancer. We propose a comprehensive framework for the analysis and reporting of PSMA-PET findings that will improve the communication between imaging experts and uro-oncologists.

Developing a novel patient-reported outcome measure for patients with prostate cancer receiving radionuclide therapy: The FACT-RNT

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Background: The field of targeted radionuclide therapy (RNT) for prostate cancer (PC) is growing rapidly with recent FDA approval of the first lutetium-177-PSMA-ligand. Commonly used patient-reported outcome (PRO) measures were originally designed to assess the impacts of traditional therapies (e.g., chemotherapy, surgery). We aimed to develop the first PRO measure for PC patients receiving RNT. Methods: We used a multi-step approach based on input from experts and patients. We identified symptoms and toxicities potentially relevant in the context of RNT for PC from a literature review of published trials and interviews with PC patients who had received RNT, caregivers of RNT recipients, and clinicians. We identified items to include in the measure from the Functional Assessment of Chronic Illness Therapy (FACIT) item library. Finally, we reviewed, refined, and finalized the new measure. Results: Potentially relevant symptoms/toxicities were identified by reviewing published trials (e.g., xerostomia, nausea). Interviews with PC patients who received RNT (n=29), caregivers (n=14), and clinicians (n=11) yielded additional symptoms/toxicities (e.g., fatigue, constipation). After selecting a broad and comprehensive list of items from the FACIT item library, we refined the list based on input from 9 experts in the field of RNTs and PROs from 5 institutions. Patients who received RNT for PC (n=11) reviewed the draft measure and confirmed items were relevant to RNT recipients and comprehensible. This resulted in a brief 15-item measure deemed by key stakeholders to be relevant and useful in the context of RNT for PC. Conclusions: The FACT-RNT (Functional Assessment of Cancer Therapy – Radionuclide Therapy) is a PRO new measure for RNT recipients developed through multi-step collaboration with patients, caregivers, clinicians, and international experts. The FACT-RNT can be used in RNT clinical trials and real-world settings.

Time interval between radium-223 (223Ra) therapy and Lutetium-177–prostate-specific membrane antigen (177Lu-PSMA) treatment and outcomes in the RALU study

73

Background: 223Ra and 177Lu-PSMA-617 both prolong overall survival (OS) in different mCRPC settings. The observational, retrospective study, RALU, investigated safety and clinical outcomes of sequential 223Ra/177Lu-PSMA therapy in patients (pts) with mCRPC. This analysis evaluated the association of time interval between 223Ra and 177Lu-PSMA treatments and safety and OS outcomes of 177Lu-PSMA. Methods: Retrospective data were collected from 2021–22 in German nuclear medicine centers for all pts receiving 177Lu-PSMA with prior history of 223Ra therapy. Time intervals were <6 months (mo) (Group [Grp]1) or ≥6 mo (Grp 2) from last 223Ra dose to first 177Lu-PSMA dose. Results: 42 pts received 177Lu-PSMA within 6 mo after 223Ra (Grp 1) and 90 pts received 223Ra ≥6 mo prior to 177Lu-PSMA (Grp 2). Baseline characteristics prior to 177Lu-PSMA therapy were, respectively: median ages 72 and 74 years; 57% and 63% with Eastern Cooperative Oncology Group performance status (ECOG PS) 1, 43% and 37% with ECOG PS 2; median prostate-specific antigen (PSA) values were 366 and 268 ng/ml, and median alkaline phosphatase (ALP) values were 133 and 149 U/L; 40% and 64% received ≥4 life prolonging therapies before starting 177Lu-PSMA. All pts had prior 223Ra; 57% and 77% received 6 223Ra injections; other prior therapies were abiraterone (60%, 77%), enzalutamide (50%, 78%), docetaxel (71%, 76%) and cabazitaxel (17%, 26%). Prior to 177Lu-PSMA, 24% and 29% of pts had visceral metastases. 45% and 52% of pts received ≥4 177Lu-PSMA cycles. From 177Lu-PSMA start to ≤30 days post last dose, 71% and 82% of pts had treatment-emergent adverse events (TEAEs) of any grade; most common were fatigue (12%, 7%), nausea (12%, 8%) and dry mouth (7%, 18%); 36% and 24% of pts had grade 3–4 TEAEs; excluding laboratory abnormalities, osteonecrosis of the jaw was the most frequent grade 3–4 TEAE (5%, 2%). Grade 3–4 laboratory abnormalities (177Lu-PSMA start to ≤90 days post last dose) are shown; treatment-related deaths were reported for 2% and 4% of pts. AEs led to treatment delays in 10% and 9% of pts. Median OS from start of 177Lu-PSMA was 12.0 mo (95% CI, 8.8–19.9) in Grp 1 and 13.2 mo (95% CI, 10.0–15.9) in Grp 2. During 177Lu-PSMA therapy, PSA response ≥50% occurred in 53% and 39% and ALP response ≥30% in 28% and 14% of pts, respectively. Conclusions: In this real-world setting, treating pts with 177Lu-PSMA within 6 mo of completing 223Ra was clinically feasible and well tolerated: no safety signals or concerns were seen. OS outcomes were similar in pts receiving 177Lu-PSMA <6 mo vs. pts receiving it ≥6 mo after completing 223Ra. [Table: see text]

Activity of lutetium-177 PSMA (Lu-PSMA) and determinants of outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with cabazitaxel: The PACAP study

180

Background: Cabazitaxel and Lu-PSMA both improved survival in patients with mCRPC after docetaxel and an androgen receptor pathway inhibitor (ARPI), but there is limited data regarding Lu-PSMA activity after cabazitaxel. We aimed at assessing activity of Lu-PSMA and determinants of outcomes in this setting. Methods: Consecutive mCRPC patients from 6 European centers treated with Lu-PSMA after cabazitaxel were included in this retrospective study. Endpoints included radiographic progression-free survival (rPFS), time to PSA progression (PSA-TTP), PSA decline, objective response, overall survival, and safety. Results: Of 101 patients included (median age 67y), 64% had ISUP grade 4-5 disease; 71% had bone +/- nodal (LN) metastases, 22% visceral metastases, 7% LN only. All patients and 92% had received previous docetaxel and a prior ARPI (≥ 2 in 47%) before cabazitaxel respectively. Patients had received a median number of 6 cabazitaxel cycles (range 1-26). DNA damage repair alterations (DDR) were found in 11/48 (23%) patients with available testing. Patients received a median number of 3 Lu-PSMA cycles (range 1-14). With a median follow-up of 5.7 months, the median rPFS from Lu-PSMA initiation was 4.3 months (m, 95%CI 3.2-5.7) and median PSA-TTP was 3.5 m (95%CI 3.0-4.5). Overall, 44 patients (44%) experienced a PSA decline ≥ 50% (PSA50), 54 (53%) ≥ 30% (PSA30), and 67 (66%) any PSA decline. Objective response rate was 34%. Baseline characteristics associated with shorter rPFS on Lu-PSMA included ISUP grade 4-5 disease (median rPFS of 3.5 vs. 7.2m, p=0.02) and a time to castration resistance < 12 months (3.1m vs. 4.5m, p=0.04). Patients with LN only had longer rPFS compared to those with bone and visceral metastases (median NR vs. 3.6 and 3.7m, respectively, p=0.02). There was no association between activity of Lu-PSMA and DNA damage repair alterations, duration of previous cabazitaxel therapy, and number of previous ARPI. During Lu-PSMA, a profound PSA decline was associated with longer rPFS: patients achieving PSA50, PSA30 or any PSA decline had respective median rPFS rates of 9.0, 8.3 and 6.2 months, while those who did not experience any PSA decline had a median rPFS of only 2.6 months. Conclusions: Lu-PSMA demonstrated substantial PSA decline but limited duration of response after cabazitaxel in a real-life setting. Adverse baseline characteristics and absence of PSA decline may help early identification of poor responders.

Predictive value of highly sensitive basal versus stimulated thyroglobulin measurement in long-term follow-up of thyroid cancer

OBJECTIVE

Recurrence of differentiated thyroid cancer (DTC) is associated with reduced quality of life, and therefore, early identification of patients at risk is urgently needed.Here we investigated the predictive power of various cut-off values of single stimulated thyroglobulin (s-Tg) and single highly sensitive measured, unstimulated thyroglobulin (u-hsTg) measurements close to the end of primary therapy for recurrence-free survival (RFS) in long-term follow-up (>10 years) of patients with DTC.

METHODS

In DTC patients with adjuvant radioiodine therapy, we assessed retrospectively u-hsTg (6 ± 3 months before s-Tg measurement) and s-Tg measurements (≤24 months after last radioiodine therapy). Positive predictive (PPV)/negative predictive values (NPV) of various cut-off values (s-Tg: 0.5/1.0 ng/mL; u-hsTg: 0.09/0.2 ng/mL) for patient outcomes as well as additional factors associated with disease development were analyzed.

RESULTS

In total, 175 patients were retrospectively reviewed (tumor recurrence: n = 14/complete remission: n = 161). Examined cut-off values for s-Tg and u-hsTg showed significant predictive power for RFS (log-rank: all P < 0.001). NPV/PPV for s-Tg were 98.6%/36.4%, respectively (0.5 ng/mL cut-off) and 96.7%/42.9%, respectively (1.0 ng/mL cut-off); those for u-hsTg were 97.3%/35.7%, respectively (0.09 ng/mL cut-off) and 95.2%/85.7%, respectively (0.2 ng/mL cut-off). U-hsTg (P < 0.001) and patient age (P < 0.05) were significantly associated with tumor recurrence. One-third of patients with tumor recurrence in the course initially showed undetectable u-hsTg after completion of primary therapy.

CONCLUSION

With >10 years of follow-up, both s-Tg and u-hsTg have a comparably high predictive power for RFS, while only u-hsTg was significantly associated with a recurrence event.Serial u-hsTg measurements seem warranted since patients with tumor recurrence during follow-up may have an undetectable tumor marker at baseline.

Developing a novel patient reported outcomes measure for prostate cancer patients receiving radionuclide therapy

The field of radionuclide therapy (RNT) for prostate cancer (PC) is growing rapidly with recent FDA approval of the first Lutetium-177-PSMA-ligand. Current patient-reported outcomes (PRO) measures were designed to assess impacts of chemotherapy or surgery. We aimed to develop the first PRO measure for PC patients receiving RNT. Methods: First, we identified relevant symptoms/toxicities by reviewing published trials and interviews with PC patients receiving RNT (n = 29), caregivers (n = 14), and clinicians (n = 11). Second, we selected items for measure inclusion. Third, we refined the item list with input from experts in RNTs and PROs. Fourth, we finalized the FACT-RNT with patient input. Results: This multi-step process yielded a brief 15-item measure deemed by key stakeholders to be relevant and useful in the context of RNT for PC. Conclusion: The Functional Assessment of Cancer Therapy - Radionuclide Therapy (FACT-RNT) is a new standardized tool to monitor relevant symptoms/toxicities in RNT trials and real-world settings.

F18-PSMA Cerenkov luminescence and flexible autoradiography Imaging in a prostate cancer mouse model and first results of a radical prostatectomy feasibility study in men

Intraoperative identification of positive resection margins (PRMs) in high-risk prostate cancer (PC) needs improvement. Cerenkov luminescence imaging (CLI) with ⁶⁸Ga-PSMA-11 is promising, although limited by low residual activity and artificial signals. Here, we aimed to assess the value of CLI and flexible autoradiography (FAR) with ¹⁸F-PSMA-1007. Methods: Mice bearing subcutaneous PSMA-avid RM1-PGLS tumors were administered ¹⁸F-PSMA-1007, and PET/CT was performed. After the animals had been killed, organs were excised and measured signals in CLI and FAR CLI were correlated with tracer activity concentrations (ACs) obtained from PET/CT. For clinical assessment, 7 high-risk PC patients underwent radical prostatectomy immediately after preoperative ¹⁸F-PSMA PET/CT. Contrast-to-noise ratios (CNRs) were calculated for both imaging modalities in intact specimens and after incision above the index lesion. Results: In the heterotopic in vivo mouse model (n = 5), CLI did not detect any lesion. FAR CLI detected a distinct signal in all mice, with a lowest AC of 7.25 kBq/mL (CNR, 5.48). After incision above the index lesion of the prostate specimen, no increased signal was observed at the cancer area in CLI. In contrast, using FAR CLI, a signal was detectable in 6 of 7 patients. The AC in the missed index lesion was 1.85 kBq/mL, resulting in a detection limit of at least 2.06 kBq/mL. Histopathology demonstrated 2 PRMs, neither of which was predicted by CLI or FAR CLI. Conclusion: ¹⁸F-PSMA FAR CLI was superior to CLI in tracer-related signal detectability. PC was could be visualized in radical prostatectomy down to 2.06 kBq/mL. However, the detection of PRMs was limited. Direct anatomic correlation of FAR CLI is challenging because of the scintillator overlay.

FDG-PET Positivity and Overall Survival in Renal Cell Carcinoma

This cohort study examines positron emission tomography in renal cell carcinoma and its association with overall survival among adults.

Impact of PSMA PET/CT on prostate cancer salvage radiotherapy management: Results from the prospective randomized phase 3 trial [PSMA SRT NCT03582774]

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Background: The purpose of the randomized PSMA SRT trial is to compare the success rate of salvage radiation therapy (SRT) for recurrence of prostate cancer (PCa) after radical prostatectomy (RP) with (intervention arm) and without (control arm) planning based on PSMA PET/CT. Here we report the secondary endpoint of the trial: impact of PSMA PET/CT on the treatment plan. Methods: This is a Randomized, controlled, prospective, open label, phase 3 clinical trial with institutional funding. 193 patients were randomized to proceed with standard SRT with any conventional imaging aside from PSMA PET/CT (control arm) or undergo a 68Ga-PSMA-11 PET/CT scan prior to SRT (investigational arm). The following information was collected on case-report forms before randomization (intended SRT plan) and after treatment: Radiation field region (prostate fossa (PF), pelvic lymph node (PLN)), total dose, dose per fraction, duration, ADT use and duration, PSMA influence on target volume, or other (free-text). Changes between SRT plan before randomization and delivered treatment were classified as Major, Minor or No Change. Major change: change of ADT duration ≥3 months, change of standard RT volumes (PF and PLN), target volume delineation beyond standard RT field, simultaneous-integrated boost (SIB) beyond standard RT fields, and initiation of advanced systemic therapy (novel ADT agents, chemotherapy). Minor change: SIB within standard RT fields. Fisher exact test was used to compare prevalence of events between study arms. Results: Enrollment is complete. 193 patients enrolled from 09.06.2018 to 8.17.2020: 90 and 103 randomized to the control group and PSMA group. Median Time from RP to enrollment and median PSA was 20.3 months (IQR 1.4–245) and 0.3 ng/ml (IQR 0.2-10.3), and 28.3 months (IQR 1.2–21) and 0.23 ng/ml (IQR 0.1-29.9), respectively. The control arm had 13 dropouts (17%) while the intervention had one (1%). PSMA was positive in 38/102 (38%): 12/102 (12%) outside of pelvis, and 20/102 (20%) in PLNs. Pre-randomization RT plan and Delivered RT plan were available in 193/193 (100%), (77/90 control (86%) and 102/103 PSMA (99%), (p = 0.0004)respectively. There were 0/77 (0%) and 7/102 (7%) minor changes in the control and PSMA groups (p = 0.02). There were 17/77 (22%) and 45/102 (44%), major changes (p = 0.004); 32/45 (71%) were PSMA-related. Treatment escalation occurred in 7/17 (41%) and 36/52 (69%) (p = 0.048), and de-escalation in 10/17 (59%) and 10/52 (19%) (p = 0.004). Nine/102 patients (9%) received advanced systemic therapy in relation to PSMA findings whereas only 1/77 (1%) patient in the control received advanced therapy (p = 0.044). Conclusions: In this prospective randomized phase 3 study, proportion of major changes between the pre-randomization SRT plan and the delivered RT plan was 44% in the PSMA intervention group and 22% in the conventional imaging control group. Clinical trial information: NCT03582774.

PSMA PET tumor-to-salivary glands ratio (PSG score) to predict response to Lu-177 PSMA radioligand therapy: An international multicenter retrospective study

5043

Background: PSMA-targeted radioligand therapy can improve the outcome of patients with advanced mCRPC. However, patients do not respond uniformly and a PSA decline of ≥50% (PSA50) was achieved only in 46% of the patients in the VISION trial. We hypothesized that using the parotid glands instead of the liver as the reference organ enables more selective stratification. The aim of this study was to test PSMA PET tumor-to-Salivary Glands ratio (PSG score) to predict outcomes after Lu-177 PSMA. Methods: This was an international multicenter retrospective study using the established dataset consisting of 270 men with mCRPC treated with Lu-177 PSMA (Gafita A, Lancet Oncol 2021). First, we assessed baseline PSMA PET quantitatively (qPSG score) to calculate the tumor-to-salivary gland ratio (qPSG = SUVmean whole-body-tumor / SUVmean parotid glands) using a semi-automatic segmentation software (qPSMA). Patients were divided into three groups: high (qPSG > 1.5), intermediate (qPSG = 0.5 - 1.5), and low (qPSG < 0.5). Second, we assessed the reproducibility and the predictive value of the PSG score visually (vPSG score) graded by ten nuclear medicine physicians. Each reader read the baseline PSMA PET 3D maximum intensity projection (MIP) images, and classified the patients into three groups: (high) most of the lesions (> 80%) show higher uptake than parotid glands; (intermediate) neither “low” nor “high”; (low) most of the lesions (> 80%) show lower uptake than parotid glands. In case of disagreement, a majority vote was used. Outcome measures were PSA-progression free-survival (PSA-PFS), overall survival (OS), and PSA50. Results: 237 men were analyzed after excluding 33 men whose parotid glands were out of the scan range. The number of the patients in the high, intermediate, and low groups were 56/237 (23.6%), 163 (68.8%), and 18 (7.6%) for qPSG score, and 106/237 (44.7%), 96 (40.5%), and 35 (14.8%) for vPSG score, respectively. The inter- and intra-readers reproducibility of the vPSG score showed substantial (Fleiss’ weighted Kappa: 0.68) and almost perfect (Cohen's weighted Kappa (mean): 0.83) agreement, respectively. The median PSA-PFS of high, intermediate, and low groups were 7.2, 4.0, and 1.9 months (p < 0.001) for qPSG score and 6.7, 3.8, and 1.9 months (p < 0.001) for vPSG score, respectively. Higher PSA50 rate was observed in the high group followed by the intermediate and low groups (high vs intermediate vs low: [qPSG] 69.6% vs 38.7% vs 16.7%; [vPSG] 63.2% vs 33.3% vs 16.1%). The median OS was longer in the high group than in the intermediate + low (i.e., non-high) group by qPSG (15.0 vs. 11.7 months (p = 0.013)) and vPSG score (14.3 vs.11.0 months (p = 0.038)). Conclusions: The PSG score is a valuable predictive biomarker for response to Lu-177 PSMA. The vPSG score yielded substantial reproducibility and comparable predictive value to the qPSG score.

Predicting the outcome of mCPRC patients after Lu-177 PSMA therapy using semi-quantitative and visual criteria in baseline PSMA PET: An international multicenter retrospective study

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Background: The aim of this study was to assess the use of the baseline PSMA parotids uptake as a reference to determine eligibility for Lu-177 PSMA radioligand therapy (RLT) by using semi-quantitative and standardized visual criteria. Methods: We conducted a retrospective cohort study using a multicenter dataset 270 men with mCRPC treated with Lu-177 PSMA (Gafita A, Lancet Oncol 2021). For quantitative analysis, semi-automatic segmentation software (qPSMA) divided men into three groups according to the SUVmean ratio of whole-body-tumor to parotid glands: (high) > 1.5; (intermediate) 0.5 - 1.5; (low) < 0.5. For visual analysis, ten nuclear medicine physicians with (n = 5) and without (n = 5) clinical experience in Lu-177 PSMA RLT ( > 50 cases) read each baseline PSMA PET 3D maximum intensity projection (MIP) images, and classified the patients into three groups: (high) most ( > 80%) of the lesions show higher uptake than parotid glands; (intermediate) neither “low” nor “high”; (low) most ( > 80%) of the lesions show lower uptake than parotid glands. In case of inter-reader disagreement, a majority vote was used. Outcome measures included PSA-progression free-survival (PSA-PFS), overall survival (OS), and PSA decline of ≥50% (PSA50). Fisher’s exact test and Kaplan–Meier analysis with the log-rank test was performed for PSA50 and survival analysis, respectively. Results: 237 men were analyzed after excluding 33 men with more than half of the parotid glands out of the PET scan field-of-view. The number of the patients in the high, intermediate, and low groups were 106/237 (44.7%), 96 (40.5%), and 35 (14.8%) for visual criteria, and 56 (23.6%), 163 (68.8%), and 18 (7.6%) for quantitative analysis, respectively. The inter- and intra-readers reproducibility of the visual scoring showed substantial (Fleiss’ weighted Kappa: 0.68) and almost perfect (Cohen's weighted Kappa (mean): 0.83) agreement, respectively. The median PSA-PFS was 6.7, 3.8, and 1.9 months (p < 0.001); and 7.2, 4.0, and 1.9 months (p < 0.001) in the high, intermediate, and low expression groups by visual and quantitative criteria, respectively. The PSA50 was 63.2%, 33.3%, and 17.1% (p < 0.001), and 69.6%, 38.7%, and 16.7% (p < 0.001) in the high, intermediate, and low expression groups by visual and quantitative criteria, respectively. OS was longer in the high PSMA expression group than in the intermediate + low (i.e., non-high) group by visual (14.3 vs.11.0 months (p = 0.038)) and quantitative criteria (15.0 vs. 11.7 months (p = 0.013)). Conclusions: Tumor-to-parotid uptake using a simple visual or semi-quantitative measure is a valuable prognostic biomarker for response in men with mCRPC treated with Lu-177 PSMA RLT.

Novel framework for treatment response evaluation using PSMA-PET/CT in patients with metastatic castration-resistant prostate cancer (RECIP): An international multicenter study

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Background: We aimed to develop a novel framework for Response Evaluation Criteria In PSMA-PET/CT (RECIP) 1.0 and a composite response classification which combines responses by PSA measurements and by RECIP 1.0 (PSA+RECIP). Methods: This was an international, multicenter, retrospective study. 124 men with mCRPC who underwent 177Lu-PSMA therapy and received PSMA-PET/CT at baseline (bPET) and at interim at 12 weeks (iPET) were included. Pairs of bPET and iPET were interpreted by consensus among three blinded readers for appearance of new lesions. Tumor lesions were segmented and total PSMA-positive tumor volume (PSMA-VOL) was obtained. Appearance of new lesions and changes in PSMA-VOL were combined to develop RECIP 1.0, which was defined as: complete response (RECIP-CR: absence of any PSMA-ligand uptake on iPET), partial response (PSMA-PR: decline ≥30% in PSMA-VOL and no appearance of new lesions), progressive disease (RECIP-PD: increase ≥20% in PSMA-VOL and appearance of new lesions), stable disease (RECIP-SD: any condition but RECIP-PR or RECIP-PD). Changes in PSA levels at 12 weeks by PCWG3 were recorded. Responses by PSA+RECIP were defined as: response (PSA decline ≥50% or RECIP-PR/CR) and progression (PSA increase ≥25% or RECIP-PD). Study's primary outcome measure was the prognostic value of RECIP 1.0 for overall survival (OS). Secondary outcome measure was the prognostic accuracy (C-index) of PSA+RECIP vs PSA responses. Results: Patients with progressive disease (RECIP-PD; n=39; 8.3 mo) had shorter OS compared to patients with stable disease (RECIP-SD; n=47; 13.1 mo; p<0.001) and to those with partial response (RECIP-PR; n=38; 21.7 mo; p<0.001). PSA+RECIP had superior C-indices in identifying responders and progressors compared to PSA only: 0.65 vs 0.62 (p=0.028) and 0.66 vs 0.63 (p=0.044), respectively. Conclusions: PSMA-PET/CT by RECIP 1.0 is prognostic for OS and can be used as a response biomarker to monitor efficacy of 177Lu-PSMA in men with mCRPC. PSA+RECIP may be used as a novel composite endpoint in mCRPC clinical trial design.

Metabolic imaging with FDG-PET and time to progression in patients discontinuing immune-checkpoint inhibition for metastatic melanoma

Background

The optimal duration of immune checkpoint blockade (ICB) therapy is not well established. Active residual disease is considered prohibitive for treatment discontinuation and its detection by diagnostic CT imaging is limited. Here, we set out to determine the potential added value of 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) to identify patients at higher risk of relapse following discontinuation of ICB in advanced melanoma.

Methods

Metastatic melanoma patients who discontinued ICB were identified retrospectively. Eligible patients received FDG-PET and diagnostic CT within four months of ICB discontinuation. We defined morphologic response using RECIST v1.1. Complete metabolic response (CMR) was defined as uptake in tumor lesions below background, whereas any site of residual, FDG-avid disease was rated as non-CMR. The primary endpoint was time to progression (TTP) after therapy discontinuation stratified by morphologic and metabolic imaging response using Kaplan–Meier estimates and log-rank test.

Results

Thiry-eight patients were eligible for this analysis. Median follow-up was 37.3 months since ICB discontinuation. Median TTP in the overall cohort was not reached. A greater proportion of patients were rated as CMR in PET (n = 34, 89.5%) as compared to complete response (CR) in CT (n = 13, 34.2%). Median TTP was reached in patients with non-CMR (12.7 months, 95%CI 4.4-not reached) but not for patients with CMR (log-rank: p < 0.001). All patients with complete response by CT had CMR by PET. In a subset of patients excluding those with complete response by CT, TTP remained significantly different between CMR and non-CMR (log-rank: p < 0.001).

Conclusion

Additional FDG-PET at time of discontinuation of ICB therapy helps identify melanoma patients with a low risk of recurrence and favourable prognosis compared to CT imaging alone. Results may have clinical relevance especially for patients with residual tumor burden.

Prostate specific membrane antigen-radio guided surgery using Cerenkov luminescence imaging-utilization of a short-pass filter to reduce technical pitfalls

Background

Intraoperative Cerenkov luminescence imaging (CLI) is a novel technique to assess surgical margins in patients undergoing nerve sparing radical prostatectomy (RP). Here, we analyze the efficacy of a 550-nm optical short-pass filter (OF) to improve its performance.

Methods

In this prospective single-center feasibility study ten patients with prostate cancer (PC) were included between December 2019 and April 2020, including three patients without tracer injection as a control group. After preoperative injection of 68-Ga-prostate-specific membrane antigen (PSMA)-11 followed by RP, CLI of the excised prostate and the incised index lesion was performed to visualize the primary tumor lesion. We compared the findings on intraoperative CLI to postoperative histopathology. Furthermore, CLI-intensities determined as tumor to background ratio (TBR) and contrast to noise ratio (CNR) were measured.

Results

Histopathology proved positive surgical margins (PSM) in 3 patients with corresponding findings in CLI. After magnetic resonance imaging (MRI)-informed incision above the index lesion 2 out of 3 prostates demonstrated elevated CLI signals with histopathological confirmation of PC cells. The use of the OF enabled a significant reduction of the area of the regions of interest from a median of 1.80 to 0.15 cm² (reduction by 85%, P=0.005) leading to increased specificity. Signals due to PSMs were not suppressed by the 550-nm OF. The median TBR was reduced from 3.33 to 2.10. In all three patients of the control group elevated CLI intensities were detected at locations with diathermal energy deposition during surgery. After application of the 550-nm OF these were almost totally suppressed with a TBR of 1.10. Measurements of Cerenkov luminescence intensity with the 550-nm OF showed a significant Pearson's correlation of 0.82 between PSM and the elevated TBR (P=0.003) and a significant Pearson's correlation of 0.66 between PSM and elevated CNR (P=0.04). Measurements without the OF did not correlate significantly.

Conclusions

Intraoperative 68-Ga-PSMA CLI in PC is a tool that warrants further investigation to visualize PSM especially in intermediate and high-risk PC. Intraoperative CLI benefits from usage of a 550-nm OF to reduce false-positive signals.

Prospective comparison of the diagnostic accuracy of 18F-FDG PET/MRI, MRI, CT, and bone scintigraphy for the detection of bone metastases in the initial staging of primary breast cancer patients

OBJECTIVES

To compare the diagnostic performance of [18F]FDG PET/MRI, MRI, CT, and bone scintigraphy for the detection of bone metastases in the initial staging of primary breast cancer patients.

MATERIAL AND METHODS

A cohort of 154 therapy-naive patients with newly diagnosed, histopathologically proven breast cancer was enrolled in this study prospectively. All patients underwent a whole-body [18F]FDG PET/MRI, computed tomography (CT) scan, and a bone scintigraphy prior to therapy. All datasets were evaluated regarding the presence of bone metastases. McNemar χ2 test was performed to compare sensitivity and specificity between the modalities.

RESULTS

Forty-one bone metastases were present in 7/154 patients (4.5%). Both [18F]FDG PET/MRI and MRI alone were able to detect all of the patients with histopathologically proven bone metastases (sensitivity 100%; specificity 100%) and did not miss any of the 41 malignant lesions (sensitivity 100%). CT detected 5/7 patients (sensitivity 71.4%; specificity 98.6%) and 23/41 lesions (sensitivity 56.1%). Bone scintigraphy detected only 2/7 patients (sensitivity 28.6%) and 15/41 lesions (sensitivity 36.6%). Furthermore, CT and scintigraphy led to false-positive findings of bone metastases in 2 patients and in 1 patient, respectively. The sensitivity of PET/MRI and MRI alone was significantly better compared with CT (p < 0.01, difference 43.9%) and bone scintigraphy (p < 0.01, difference 63.4%).

CONCLUSION

[18F]FDG PET/MRI and MRI are significantly better than CT or bone scintigraphy for the detection of bone metastases in patients with newly diagnosed breast cancer. Both CT and bone scintigraphy show a substantially limited sensitivity in detection of bone metastases.

KEY POINTS

• [18F]FDG PET/MRI and MRI alone are significantly superior to CT and bone scintigraphy for the detection of bone metastases in patients with newly diagnosed breast cancer. • Radiation-free whole-body MRI might serve as modality of choice in detection of bone metastases in breast cancer patients.

Comparison of nodal staging between CT, MRI, and [18F]-FDG PET/MRI in patients with newly diagnosed breast cancer

PURPOSE

To compare CT, MRI, and [¹⁸F]-fluorodeoxyglucose positron emission tomography ([¹⁸F]-FDG PET/MRI) for nodal status, regarding quantity and location of metastatic locoregional lymph nodes in patients with newly diagnosed breast cancer.

MATERIALS AND METHODS

One hundred eighty-two patients (mean age 52.7 ± 11.9 years) were included in this prospective double-center study. Patients underwent dedicated contrast-enhanced chest/abdomen/pelvis computed tomography (CT) and whole-body ([¹⁸F]-FDG PET/) magnet resonance imaging (MRI). Thoracal datasets were evaluated separately regarding quantity, lymph node station (axillary levels I-III, supraclavicular, internal mammary chain), and lesion character (benign vs. malign). Histopathology served as reference standard for patient-based analysis. Patient-based and lesion-based analyses were compared by a McNemar test. Sensitivity, specificity, positive and negative predictive values, and accuracy were assessed for all three imaging modalities.

RESULTS

On a patient-based analysis, PET/MRI correctly detected significantly more nodal positive patients than MRI (p < 0.0001) and CT (p < 0.0001). No statistically significant difference was seen between CT and MRI. PET/MRI detected 193 lesions in 75 patients (41.2%), while MRI detected 123 lesions in 56 patients (30.8%) and CT detected 104 lesions in 50 patients, respectively. Differences were statistically significant on a lesion-based analysis (PET/MRI vs. MRI, p < 0.0001; PET/MRI vs. CT, p < 0.0001; MRI vs. CT, p = 0.015). Subgroup analysis for different lymph node stations showed that PET/MRI detected significantly more lymph node metastases than MRI and CT in each location (axillary levels I-III, supraclavicular, mammary internal chain). MRI was superior to CT only in axillary level I (p = 0.0291).

CONCLUSION

[¹⁸F]-FDG PET/MRI outperforms CT or MRI in detecting nodal involvement on a patient-based analysis and on a lesion-based analysis. Furthermore, PET/MRI was superior to CT or MRI in detecting lymph node metastases in all lymph node stations. Of all the tested imaging modalities, PET/MRI showed the highest sensitivity, whereas CT showed the lowest sensitivity, but was most specific.

Response to combined peptide receptor radionuclide therapy and checkpoint immunotherapy with ipilimumab plus nivolumab in metastatic Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine cancer of the skin. For patients who are refractory to immune checkpoint inhibition (ICI), treatment options are limited. Few cases of MCCs with high somatostatin receptor (SSTR) expression were reported to show responses upon SSTR-directed peptide receptor radionuclide therapy (PRRT). A combination of PRRT and ICI has not been reported in MCC to date. A 60-year old man with metastatic MCC, who was primarily resistant to the anti-PD-L1 ICI with avelumab and secondarily resistant to the anti-CTLA4 plus anti-PD-1 ICI therapy with ipilimumab plus nivolumab (IPI/NIVO) with additional RT, presented with multiple bone and lymph node metastases. After confirmation of SSTR expression, the patient was treated with a salvage therapy of additional four doses of IPI/NIVO combined with two cycles of PRRT. Treatment was well tolerated with transient hematoxicity and mild nausea. Re-staging three months after therapy start showed an exceptional good response. This case report demonstrates the feasibility of a combined treatment with IPI/NIVO and PRRT as a salvage option for MCC patients progressing under ICI therapy. Prospective evidence confirming the additive value of combining ICI and radionuclide therapy in a larger cohort is needed.

Silicon-photomultiplier-based PET/CT reduces the minimum detectable activity of iodine-124

The radioiodine isotope pair 124I/131I is used in a theranostic approach for patient-specific treatment of differentiated thyroid cancer. Lesion detectability is notably higher for 124I PET (positron emission tomography) than for 131I gamma camera imaging but can be limited for small and low uptake lesions. The recently introduced silicon-photomultiplier-based (SiPM-based) PET/CT (computed tomography) systems outperform previous-generation systems in detector sensitivity, coincidence time resolution, and spatial resolution. Hence, SiPM-based PET/CT shows an improved detectability, particularly for small lesions. In this study, we compare the size-dependant minimum detectable 124I activity (MDA) between the SiPM-based Biograph Vision and the previous-generation Biograph mCT PET/CT systems and we attempt to predict the response to 131I radioiodine therapy of lesions additionally identified on the SiPM-based system. A tumour phantom mimicking challenging conditions (derived from published patient data) was used; i.e., 6 small spheres (diameter of 3.7-9.7 mm), 9 low activity concentrations (0.25-25 kBq/mL), and a very low signal-to-background ratio (20:1). List-mode emission data (single-bed position) were divided into frames of 4, 8, 16, and 30 min. Images were reconstructed with ordinary Poisson ordered-subsets expectation maximization (OSEM), additional time-of-flight (OSEM-TOF) or TOF and point spread function modelling (OSEM-TOF+PSF). The signal-to-noise ratio and the MDA were determined. Absorbed dose estimations were performed to assess possible treatment response to high-activity 131I radioiodine therapy. The signal-to-noise ratio and the MDA were improved from the mCT to the Vision, from OSEM to OSEM-TOF and from OSEM-TOF to OSEM-TOF+PSF reconstructed images, and from shorter to longer emission times. The overall mean MDA ratio of the Vision to the mCT was 0.52 ± 0.18. The absorbed dose estimations indicate that lesions ≥ 6.5 mm with expected response to radioiodine therapy would be detectable on both systems at 4-min emission time. Additional smaller lesions of therapeutic relevance could be detected when using a SiPM-based PET system at clinically reasonable emission times. This study demonstrates that additional lesions with predicted response to 131I radioiodine therapy can be detected. Further clinical evaluation is warranted to evaluate if negative 124I PET scans on a SiPM-based system can be sufficient to preclude patients from blind radioiodine therapy.

Lung uptake detected by 68Ga-PSMA-11 PET/CT in prostate cancer patients with SARS-CoV-2: a case series

Coronavirus disease 2019 (COVID-19) pathology is associated with neoangiogenesis and interstitial pneumonia. ⁶⁸Ga-PSMA-11-PET/CT is able to image in vivo PSMA (Prostate-Specific Membrane Antigen) expression on both prostate cancer (PCa) cells and neovasculature endothelial cells. The aim of the case series was to explore pulmonary PSMA expression not related to cancer in patients with PCa and concomitant COVID-19. In this retrospective, multicenter case series, patients who underwent ⁶⁸Ga-PSMA-11-PET/CT for PCa and concomitant proven COVID-19 infection were analyzed. Patients were stratified according to ⁶⁸Ga-PSMA-11 intensity of uptake in the lung (SUV_max). Low uptake: < blood pool; mild-to-moderate uptake: > blood pool and < liver; intense uptake: > liver. Potential correlation between pulmonary ⁶⁸Ga-PSMA-11 uptake not related to PCa and CT patterns typical for COVID-19 was assessed. Nine patients were included, all of them presenting abnormal ⁶⁸Ga-PSMA-11 uptake, at different grades: 2/9 low, 6/9 mild-to-moderate, 1/9 high. Uptake distribution was generally bilateral, peripheral and posterior, positively matching with ground-glass CT alterations in 7/9 (78%) patients, while mismatch was observed in 2/9 (22%). 1/9 patients presented PCa lung metastases at ⁶⁸Ga-PSMA-11. ⁶⁸Ga-PSMA-11-PET/CT detected increased PSMA uptake within the lung, not related to PCa, matching with CT typical COVID-19 patterns in almost all patients. Further studies are needed to evaluate the role of ⁶⁸Ga-PSMA-11 PET in COVID-19 patients and the potential role of PSMA overexpression as a biomarker for neoangiogenesis, in both oncological and infective disorders.

Theranostics in oncology: What radiologists want to know

Combination of radioligand imaging and therapy, so called radiotheranostics, is a novel tool of precision oncology with proven clinical value. In-depth knowledge of functional imaging nuances is critically needed for precise prognostication and guidance of management. Here, we review theranostic applications with up to Phase III type evidence for outcome improvement: Imaging and therapy of neuroendocrine neoplasms (NEN) exploiting high levels of somatostatin receptor (SSTR) expression and radiotheranostics of prostate cancer targeting the prostate specific membrane antigen (PSMA). This narrative review focusses on these two applications and elucidates patient selection and response assessment by radioligand scintigraphy and/or positron emission tomography. Furthermore, we provide a brief outlook on future applications for novel targets outside of NEN and prostate cancer.

Cardiac fibroblast activation detected by Ga-68 FAPI PET imaging as a potential novel biomarker of cardiac injury/remodeling

BACKGROUND

Fibroblast activation protein (FAP) as a specific marker of activated fibroblasts can be visualized by positron emission tomography (PET) using Ga-68-FAP inhibitors (FAPI). Gallium-68-labeled FAPI is increasingly used in the staging of various cancers. In addition, the first cases of theranostic approaches have been reported. In this work, we describe the phenomenon of myocardial FAPI uptake in patients who received a Ga-68 FAPI PET for tumor staging.

METHOD AND RESULTS

Ga-68 FAPI PET examinations for cancer staging were retrospectively analyzed with respect to cardiac tracer uptake. Standardized uptake values (SUV) were correlated to clinical covariates in a univariate regression model. From 09/2018 to 11/2019 N = 32 patients underwent FAPI PET at our institution. Six out of 32 patients (18.8%) demonstrated increased localized myocardial tracer accumulation, with remote FAPI uptake being significantly higher in patients with vs without localized focal myocardial uptake (SUVmax 2.2 ± .6 vs 1.5 ± .4, P < .05 and SUVmean 1.6 ± .4 vs 1.2 ± .3, P < .05, respectively). Univariate regression demonstrated a significant correlation of coronary artery disease (CAD), age and left ventricular ejection fraction (LVEF) with remote SUVmean uptake, the latter with a very strong correlation with remote uptake (R2 = .74, P < .01).

CONCLUSION

Our study indicates an association of CAD, age, and LVEF with FAPI uptake. Further studies are warranted to assess if fibroblast activation can be reliably measured and may be used for risk stratification regarding early detection or progression of CAD and left ventricular remodeling.

Complete metabolic response in advanced non-small cell lung cancer patients with prolonged response to immune checkpoint inhibitor therapy

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Background: Recently reported, extended follow-up data from KEYNOTE-024 or -010 indicates that non-small-cell lung cancer (NSCLC) patients can experience long-term benefit from immunotherapy irrespective of discontinuation (per protocol: 35 cycles ∼24 months) or type of response in computed tomography (CT). Similar results were observed in the pooled analysis of 5-year follow-up data from CheckMate-017 and -057. This raises the question, whether patients may safely discontinue immunotherapy after achieving durable response. However, recently published results from CheckMate-153 demonstrated inferior survival rates in patients ceasing immunotherapy after one year, therefore optimal treatment duration of immunotherapy in advanced NSCLC remains unknown. Protocols from published Phase-III trials implemented treatment for a period of approximately 24 months or until evidence of disease progression or unbearable toxicity. Therefore, the ideal duration of immunotherapy remains unclear, and finding markers of beneficial outcome is of great importance. Here, we determine the proportion of complete metabolic responses (CMR) in patients that have not progressed after 24 months of immunotherapy. Methods: This is a retrospective analysis of forty-five patients with positron emission tomography using 2-[18F]fluoro-2-deoxy-D-glucose (FDG-PET) imaging for assessment of residual metabolic activity after at least 24 months of immunotherapy. Lesion-uptake in FDG PET on or below background level (using mediastinum as reference) was considered as CMR. Time until best objective morphological response including disease stabilization was measured from start of immunotherapy until first stable CT-scan (i.e. no progression or further response compared to previous scan) using RECIST 1.1. Results: Out of 45 patients, 29 patients had a CMR (64%). CMR was observed more frequently in non-first line patients. Patients with CMR were younger (median 65.7 vs. 75.5, P = 0.03). Fourteen patients with CMR have discontinued therapy and have not progressed until time of analysis; however median follow-up was only 5.6 (range 0.8-17.0) months. Conclusions: After a minimum of 24 months of palliative immunotherapy for NSCLC, CMR occurred in almost two thirds of patients. Potentially, achievement of CMR might identify patients, for whom palliative immunotherapy may be safely discontinued.

Interim PSMA PET/CT for response evaluation during LuPSMA treatment in mCRPC (INTERIM PET): An explorative, multicenter study

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Background: The aim of this analysis was to evaluate the prognostic value of interim PSMA PET/CT in men with metastatic castration-resistant prostate cancer (mCRPC) treated with 177Lu-PSMA and to develop a novel framework for Response Evaluation Criteria In PSMA-imaging (RECIP). Methods: This was an explorative, multicenter, retrospective study; 124 men with mCRPC who underwent 177Lu-PSMA treatment and received PSMA-PET/CT at baseline (bPET) and at interim after two cycles of treatment (iPET) met the eligibility criteria and were included in this analysis. The primary endpoint was overall survival (OS). Pairs of bPET and iPET were interpreted by three independent readers for appearance of new lesions. Whole-body tumor lesions were segmented using qPSMA software and total PSMA-positive tumor volume (PSMA-VOL) was obtained. Changes in PSMA-VOL on iPET relative to bPET were calculated. After being tested separately for associations with OS, appearance of new lesions and changes in PSMA-VOL were combined to develop RECIP. Results: The median OS was 13.5 months (95%CI, 11.6-15.4). Appearance of at least one new lesion on iPET was observed in 73 (59%) patients and was associated with poor OS (hazard ratio [HR] 2.23; 95%CI, 1.51-3.28; P <.001). Based on the current data, RECIP were defined as: partial response (PSMA-PR) as a decline ≥20% in PSMA-VOL and no appearance of new lesions; progressive disease (PSMA-PD) as an increase ≥20% in PSMA-VOL and appearance of new lesions; stable disease (PSMA-SD) was defined as any condition but not PSMA-PR or PSMA-PD. The OS of men with PSMA-PD (n = 41) was significantly worse compared to men with PSMA-SD (n = 47; HR 2.52; 95%CI, 1.61–3.93; P <.001) and PSMA-PR (n = 36; HR 4.16; 95%CI, 2.54–6.78; P <.001). PSMA-SD was associated with significantly worse OS compared to PSMA-PR (HR 1.65; 95%CI, 1.02–2.65; P =.039). The time dependent C-index of associations with OS for response according to RECIP was 0.68 (95%CI, 0.63-0.72). Conclusions: Interim staging using PSMA-PET/CT and response classification by RECIP is prognostic for survival of men with mCRPC treated with 177Lu-PSMA. Validation of these findings in clinical trials is warranted.

FDG-PET avidity as a prognostic biomarker for overall survival in renal cell carcinoma

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Background: Positron emission tomography with (18F)-fluorodeoxyglucose (FDG-PET) is not considered a standard of care (SOC) in renal cell carcinoma (RCC) because of its variability in metabolic activity. We investigated the rate of PET-positivity in our institutional cohort and tested whether PET-positivity had prognostic value in metastatic (m)RCC. Methods: Patients with FDG-PET imaging at any time during the course of disease were identified from medical records. PET-positivity was defined according to PERCIST criteria and a five-point rating scale analogue to Deauville Scoring was used to stratify PET-avidity. Tracer uptake of the hottest lesion was measured as SUVmax. Clinical parameters and PET-positivitywere correlated with overall survival (OS). Kaplan-Meier plots, log-rank analyses, kendall rank correlation, univariate and multivariable cox regression models were employed, where appropriate. Results: A totalof 90 patients was analyzed. The median age was 64.0 (34.0-83.0) and 56 (62.2%) patients had clear cell RCC. Metastatic disease was present in 64 (71.1%) and 22 (24.4%) patients received ongoing medical treatment. 72 (80.0%) patients had prior nephrectomy. PET-positivity occurred in 57 (63.3%) patients, with similar rates among metastatic (41/64; 64%) and non-metastatic patients (16/26; 62%). PET-positive patients had shorter median OS compared to PET-negative patients (38.5 months (CI95:24.5-NR) vs. not reached (CI95: 69.6-NR), P= 0.0013). A weak correlation was found between PET-Uptake and histologic grade (Kendall’s tau 0.22; P= 0.03). Prior nephrectomy, presence of primary lesions, presence of distant metastases, histologic grade and PET-positivity were significant predictors of OS in univariate regression. In multivariable analysis, only PET-positivity remained significant (HR 4.1 (CI95: 1.1-15.4), P= 0.04). Conclusions: RCC is a metabolically active cancer, which in the majority of patients is suitable for FDG-PET diagnostic procedures. PET-positivity was an independent prognostic factor for OS in RCC, indicating its putative clinical use. Further studies to define the role of FDG-PET imaging in RCC are ongoing.

Determining the axillary nodal status with four current imaging modalities including 18F-FDG PET/MRI in newly diagnosed breast cancer: A comparative study using histopathology as reference standard

Purpose: To compare breast magnetic resonance imaging (MRI), thoracal MRI, thoracal 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET)/MRI and axillary sonography for the detection of axillary lymph node metastases in women with newly diagnosed breast cancer. Materials and Methods: This prospective double-center study included patients with newly diagnosed breast cancer between March 2018 and December 2019. Patients underwent thoracal (18F-FDG PET/)MRI, axillary sonography, and dedicated prone breast MRI. Datasets were evaluated separately regarding nodal status (nodal+ vs. nodal-). Histopathology served as reference standard in all patients. The diagnostic performance of breast MRI, thoracal MRI, thoracal PET/MRI and axillary sonography in detecting nodal positive patients was tested by creating receiver-operating-characteristic curves (ROC) with a calculated area under the curve (AUC). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated for all four modalities. A McNemar test was used to assess differences. Results: 112 female patients (mean age 53.04 ± 12.6 years) were evaluated. Thoracal PET/MRI showed the highest ROC-AUC with a value of 0.892. The AUC for breast MRI, thoracal MRI and sonography were 0.782, 0.814 and 0.834, respectively. Differences between thoracal PET/MRI and axillary sonography, thoracal MRI and breast MRI were statistically significant (PET/MRI vs. axillary sonography, P = 0.01; PET/MRI vs. thoracal MRI, P = 0.02; PET/MRI vs. breast MRI, P = 0.03). PET/MRI showed the highest sensitivity (81.8%, 36/44) (95%-CI: 67.29-91.81%) while axillary sonography had the highest specificity (98.5%, 65/66), 95%-CI: 91.84-99.96%). Conclusion: 18F-FDG PET/MRI outperforms axillary sonography, breast MRI and thoracal MRI in determining the axillary lymph node status. In a clinical setting, the combination of 18F-FDG PET/MRI and axillary sonography might be considered to provide even more accuracy in diagnosis.

Ga-68-FAPI as diagnostic tool in sarcoma: Data from the FAPI-PET prospective observational trial

Introduction: Bone and soft tissue sarcomas express fibroblast activation protein (FAP) on tumor cells and associated fibroblast. Therefore, FAP is a promising therapeutic and diagnostic target. Novel radio-labelled FAP-Inhibitors (e.g. ⁶⁸Ga-FAPI46) have shown high tumor uptake in positron emission tomography (PET) in sarcoma patients. Here we report endpoints of the FAPI-PET prospective observational trial. Methods: Forty-seven patients with bone or soft tissue sarcomas undergoing clinical ⁶⁸Ga-FAPI-PET were eligible for enrollment into the FAPI-PET observational trial. Of these patients, 43 patients also underwent ¹⁸F-Fluordesoxyglucose PET (FDG). The primary study endpoint was the association of ⁶⁸Ga-FAPI-PET uptake intensity and histopathological FAP-expression analyzed with Spearman's r correlation. Secondary endpoints were detection rate, positive predictive value (PPV), interreader reproducibility, and change in management. Datasets were interpreted by two blinded readers. Results: Primary endpoint was met and the association between FAPI-PET uptake intensity and histopathological FAP-expression was significant (Spearman's r = 0.43; P = 0.03). By histopathological validation PPV was 1.00 (95% CI, 0.87-1.00) on a per-patient and 0.97 (95% CI, 0.84-1.00) on a per-region basis. In cases with histopathologic validation, 27 of 28 (96%) confirmed patients and 32 of 34 (94%) confirmed regions were PET positive resulting in an SE of 0.96 (95%CI, 0.82-1.00) on a per-patient and 0.94 (95%CI, 0.80-0.99) on a per-region basis. The detection rate on a per-patient basis in FAPI- and FDG-PET was 76.6% and 81.4%, respectively. In 8 (18.6%) patients FAPI-PET resulted in an upstaging compared to FDG-PET. FAPI-PET readers showed substantial to almost perfect agreement for the defined regions (Fleiss kappa: primary κ = 0.78; local nodal κ = 0.54; distant nodal κ = 0.91; lung κ = 0.86; bone κ = 0.69 and other κ = 0.65). Clinical management changed in 13 (30%) patients after FAPI-PET. Conclusion: We confirm an association of tumoral FAPI-PET uptake intensity and histopathological FAP expression in sarcoma patients. Further, using blinded reads and independent histopathological validation we report high PPV and sensitivity of FAPI-PET for sarcoma staging.

Complete metabolic response in patients with advanced nonsmall cell lung cancer with prolonged response to immune checkpoint inhibitor therapy

Introduction

Immunotherapy is the new standard of care in advanced non-small cell lung cancer (NSCLC). Recently published data show that treatment discontinuation after 12 months of nivolumab treatment is associated with shorter survival. Therefore, the ideal duration of immunotherapy remains unclear, and finding markers of beneficial outcomes is of great importance. Here, we determine the proportion of complete metabolic responses (CMR) in patients who have not progressed after 24 months of immunotherapy.

Methods

This is a retrospective analysis of 45 patients with positron emission tomography using 2-[18F]fluoro-2-deoxy-D-glucose imaging for assessment of residual metabolic activity after at least 24 months. CMR was defined as uptake in tumor lesions below background levels, using mediastinum as a reference.

Results

Out of 45 patients, 29 patients had a CMR (64%). CMR was observed more frequently in non-first-line patients. Patients with CMR were younger (median 65.7 vs 75.5, p=0.03). Fourteen patients with CMR have discontinued therapy and have not progressed until time of analysis; however, median follow-up was only 5.6 (range 0.8–17.0) months.

Conclusion

After a minimum of 24 months of palliative immunotherapy for NSCLC, CMR occurred in almost two thirds of patients. Potentially, achievement of CMR might identify patients, for whom palliative immunotherapy may be safely discontinued.

Evaluation of [68Ga]Ga-PSMA PET/CT images acquired with a reduced scan time duration in prostate cancer patients using the digital biograph vision

Aim

[⁶⁸Ga]Ga-PSMA-11 PET/CT allows for a superior detection of prostate cancer tissue, especially in the context of a low tumor burden. Digital PET/CT bears the potential of reducing scan time duration/administered tracer activity due to, for instance, its higher sensitivity and improved time coincidence resolution. It might thereby expand [⁶⁸Ga]Ga-PSMA-11 PET/CT that is currently limited by ⁶⁸Ge/⁶⁸Ga-generator yield. Our aim was to clinically evaluate the influence of a reduced scan time duration in combination with different image reconstruction algorithms on the diagnostic performance.

Methods

Twenty prostate cancer patients (11 for biochemical recurrence, 5 for initial staging, 4 for metastatic disease) sequentially underwent [⁶⁸Ga]Ga-PSMA-11 PET/CT on a digital Siemens Biograph Vision. PET data were collected in continuous-bed-motion mode with a mean scan time duration of 16.7 min (reference acquisition protocol) and 4.6 min (reduced acquisition protocol). Four iterative reconstruction algorithms were applied using a time-of-flight (TOF) approach alone or combined with point-spread-function (PSF) correction, each with 2 or 4 iterations. To evaluate the diagnostic performance, the following metrics were chosen: (a) per-region detectability, (b) the tumor maximum and peak standardized uptake values (SUVmax and SUVpeak), and (c) image noise using the liver’s activity distribution.

Results

Overall, 98% of regions (91% of affected regions) were correctly classified in the reduced acquisition protocol independent of the image reconstruction algorithm. Two nodal lesions (each ≤ 4 mm) were not identified (leading to downstaging in 1/20 cases). Mean absolute percentage deviation of SUVmax (SUVpeak) was approximately 9% (6%) for each reconstruction algorithm. The mean image noise increased from 13 to 21% (4 iterations) and from 10 to 15% (2 iterations) for PSF + TOF and TOF images.

Conclusions

High agreement at 3.5-fold reduction of scan time in terms of per-region detection (98% of regions) and image quantification (mean deviation ≤ 10%) was demonstrated; however, small lesions can be missed in about 10% of patients leading to downstaging (T1N0M0 instead of T1N1M0) in 5% of patients. Our results suggest that a reduction of scan time duration or administered [⁶⁸Ga]Ga-PSMA-11 activities can be considered in metastatic patients, where missing small lesions would not impact patient management. Limitations include the small and heterogeneous sample size and the lack of follow-up.

Impact of PSMA PET/CT on SRT planning: Preliminary results from the randomized phase III trial NCT03582774

30

Background: The purpose of this trial is to evaluate the success rate of salvage radiation therapy (SRT) for recurrence of prostate cancer (PCa) after radical prostatectomy with and without planning based on prostate specific membrane antigen (PSMA) positron emission tomography (PET). Methods: This is a multicenter, prospective, randomized, controlled, open-label, Phase 3 clinical imaging trial powered for clinical outcome at 5 years. UCLA is the leading central site in which PSMA PET, clinical follow-up and data management are being done. UCSF was a participating site in which PSMA PET imaging can be done. SRT can be performed anywhere, patients are followed remotely by the UCLA investigators. Patients scheduled for SRT for recurrence after primary prostatectomy and with PSA ≥ 0.1ng/ml at time of enrollment were eligible. Patients were randomized to proceed with standard SRT allowing for any conventional imaging aside from PSMA PET/CT (control arm) or undergo a 68Ga-PSMA-11 PET/CT scan prior to SRT planning (investigational arm). The primary endpoint is the success rate of SRT at 5 years in patients who undergo SRT. We report here the preliminary results of a secondary endpoint: the impact of PSMA PET on SRT planning by comparing the pre-randomization RT plans prospectively obtained on surveys before randomization to the actually delivered RT plans obtained after follow-up. Results: Enrollment of the trial was complete. 193 patients were enrolled from 09.06.2018 to 08.17.2020. 7/90 patients (9%) in the control arm dropped-out the study because they underwent a PSMA PET at another institution, while 1/103 (1%) patients of the intervention arm dropped-out due to COVID-19 related complications. After a median follow-up of 13.3 months (last follow-up date 09/01/2020), delivered RT plans were obtained in 60/83 (72%) and 70/102 (69%) of patients of the control and the PSMA arms, respectively. Median PSA at enrollment was 0.32 ng/ml (IQR 0.17-1.35) and 0.22 ng/ml (IQR 0.14-0.50) in the control and PSMA arms, respectively. There was a change between the intended pre-randomization RT plan and the actually delivered RT plan in 17/60 (28%) and 40/70 (57%) of the patients in the control and PSMA arms, respectively (p = 0.002). SRT was aborted in favor of systemic therapy and/or metastasis directed RT for extra-pelvic M1 disease in 2/60 (3%) and 12/70 (17%) of the control and PSMA arms, respectively (p = 0.17). Dose prescription and/or target volume delineation was changed in 2/60 (3%) and 1/70 (26%) in the control and PSMA arms, respectively (p = 0.001). Conclusions: In this prospective randomized phase 3 study, PSMA PET had an impact on the SRT plan in more than half of the patients. Long-term follow-up will show if the impact of PSMA PET on SRT planning translates into improved outcome or not. Clinical trial information: NCT03582774.

Phase III randomized trial of PSMA PET prior to definitive radiation therapy for unfavorable intermediate-risk or high-risk prostate cancer [PSMA dRT]: Study protocol NCT04457245

TPS172

Background: Definitive radiation therapy (dRT) is an effective initial treatment of intermediate-risk (IR) and high-risk (HR) prostate cancer (PCa). Positron emission tomography (PET) using small molecule probes targeting prostate-specific membrane antigen (PSMA PET) is superior to standard of care imaging (CT, MRI, bone scan) for detecting regional and distant metastatic PCa. PSMA PET thus has the potential to guide primary radiotherapy planning in patients and improve outcomes. The purpose of the present randomized trial is to evaluate the success rate of dRT for IR or HR PCa with and without planning based on PSMA PET. Methods: We will randomize 312 patients to proceed with standard dRT (control Arm 1, n=150), or undergo a PSMA PET scan prior to dRT planning (intervention arm 2, n = 162). In the control arm, dRT will be performed as routinely planned in accordance with initial stratification. In the intervention arm, the treating radiation oncologist can incorporate PSMA PET findings into the RT planning. We assume that approximately 8% of subjects randomized to arm 2 will be found to have M1 disease and thus will be more appropriate candidates for long-term systemic or multimodal therapy, rather than curative intent dRT. PET M1 patients will thus not be included in the analysis of the primary endpoint. The primary endpoint is the success rate of dRT measured as PFS after initiation of dRT. Progression is defined as (whichever occurs first): biochemical recurrence defined as a rise by 2 ng/mL or more above the nadir PSA (defined as the lowest PSA achieved) after radiotherapy with or without short-term hormonal therapy; appearance of metastasis or loco-regional recurrence (diagnosed by any imaging or biopsy); initiation of any new salvage therapy, or death from any cause. Discussion: This is the first randomized phase 3 prospective trial designed to determine whether PSMA PET molecular imaging can improve outcomes in patients with PCa who receive dRT. In this trial the incorporation of PSMA PET may improve the success rate of curative intent radiotherapy in two ways: to optimize patient selection and to personalizes the radiotherapy plan. Clinical trial registration: IND#147591, UCLA IRB #20-000378, ClinicalTrials.gov Identifier NCT04457245. Clinical trial information: NCT04457245.

Comparing lesion detection efficacy and image quality across different PET system generations to optimize the iodine-124 PET protocol for recurrent thyroid cancer

Background

In recurrent differentiated thyroid cancer patients, detectability in ¹²⁴I PET is limited for lesions with low radioiodine uptake. We assess the improvements in lesion detectability and image quality between three generations of PET scanners with different detector technologies. The results are used to suggest an optimized protocol.

Methods

Datasets of 10 patients with low increasing thyroglobulin or thyroglobulin antibody levels after total thyroidectomy and radioiodine therapies were included. PET data were acquired and reconstructed on a Biograph mCT PET/CT (whole-body, 4-min acquisition time per bed position; OSEM, OSEM-TOF, OSEM-TOF+PSF), a non-TOF Biograph mMR PET/MR (neck region, 4 min and 20 min; OSEM), and a new generation Biograph Vision PET/CT (whole-body, 4 min; OSEM, OSEM-TOF, OSEM-TOF+PSF). The 20-min image on the mMR was used as reference to calculate the detection efficacy in the neck region. Image quality was rated on a 5-point scale.

Results

All detected lesions were in the neck region. Detection efficacy was 8/9 (Vision OSEM-TOF and OSEM-TOF+PSF), 4/9 (Vision OSEM), 3/9 (mMR OSEM and mCT OSEM-TOF+PSF), and 2/9 (mCT OSEM and OSEM-TOF). Median image quality was 4 (Vision OSEM-TOF and OSEM-TOF+PSF), 3 (Vision OSEM, mCT OSEM-TOF+PSF, and mMR OSEM 20-min), 2 (mCT OSEM-TOF), 1.5 (mCT OSEM), and 1 (mMR OSEM 4 min).

Conclusion

At a clinical standard acquisition time of 4 min per bed position, the new generation Biograph Vision using a TOF-based image reconstruction demonstrated the highest detectability and image quality and should, if available, be preferably used for imaging of low-uptake lesions. A prolonged acquisition time for the mostly affected neck region can be useful.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00361-y.

Evaluation of 18F-FDG PET/CT images acquired with a reduced scan time duration in lymphoma patients using the digital biograph vision

BACKGROUND

The superior accuracy and sensitivity of 18F-FDG-PET/CT in comparison to morphological imaging alone leads to an upstaging in up to 30% of lymphoma patients. Novel digital PET/CT scanners might enable to reduce administered tracer activity or scan time duration while maintaining diagnostic performance; this might allow for a higher patient throughput or a reduced radiation exposure, respectively. In particular, the radiation exposure reduction is of interest due to the often young age and high remission rate of lymphoma patients.

METHODS

Twenty patients with (suspected) lymphoma (6 for initial staging, 12 after systemic treatment, 2 in suspicion of recurrence) sequentially underwent 18F-FDG-PET/CT examinations on a digital PET/CT (Siemens Biograph Vision) with a total scan time duration of 15 min (reference acquisition protocol) and 5 min (reduced acquisition protocol) using continuous-bed-motion. Both data sets were reconstructed using either standalone time of flight (TOF) or in combination with point spread function (PSF), each with 2 and 4 iterations. Lesion detectability by blinded assessment (separately for supra- and infradiaphragmal nodal lesions and for extranodal lesions), lesion image quantification, and image noise were used as metrics to assess diagnostic performance. Additionally, Deauville Score was compared for all patients after systemic treatment.

RESULTS

All defined regions were correctly classified in the images acquired with reduced emission time, and therefore, no changes in staging were observed. Lesion quantification was acceptable, that is, mean absolute percentage deviation of maximum and peak standardized uptake values were 6.8 and 6.4% (derived from 30 lesions). A threefold reduction of scan time duration led to an increase in image noise from 7.1 to 11.0% (images reconstructed with 4 iterations) and from 4.7 to 7.2% (images reconstructed with 2 iterations). No deviations in Deauville Score were observed.

CONCLUSION

These results suggest that scan time duration or administered tracer activity can be reduced threefold without compromising diagnostic performance. Especially a reduction of administered activity might allow for a lower radiation exposure and better health economics. Larger trials are warranted to confirm our results.

Outcome After 68Ga-PSMA-11 versus Choline PET-Based Salvage Radiotherapy in Patients with Biochemical Recurrence of Prostate Cancer: A Matched-Pair Analysis

The purpose of this analysis was primarily to analyze biochemical-recurrence free survival (BRFS) after positron emission tomography (PET)-guided salvage radiotherapy (sRT) in a large cohort, and to further compare BRFS after PSMA vs. choline PET/ computer tomography (CT)-based sRT. This retrospective analysis is based on 421 patients referred for PSMA or choline PET/CT after radical prostatectomy due to biochemically recurrent or persistent disease. BRFS (PSA: 0.2 ng/mL) was defined as the study endpoint. Cox regression analyses were performed to assess the impact of different clinical parameters on BRFS. Additionally, propensity score matching was performed to adjust patient cohorts (PSMA vs. choline PET/CT-based sRT). The median follow-up time was 30 months. BRFS at three years after sRT was 58%. In the multivariate analysis, only PSA before PET imaging and PSA before sRT were significantly associated with BRFS (p < 0.05). After propensity score matching, 272 patients were further analyzed; there was no significant difference in three-year BRFS between patients with PSMA PET-based vs. choline PET-based sRT (55% vs. 63%, p = 0.197). The present analysis confirmed the overall high BRFS rates after PET-based sRT and the strong prognostic effect of PSA level prior to sRT. PSMA PET-based sRT did not have superior BRFS rates when compared with choline PET-based sRT.

Overall survival after 177Lu-PSMA-617 molecular radiotherapy in patients with metastatic castrate-resistant prostate cancer: Post-hoc analysis of a prospective phase II trial

5549

Background: This was an open-label randomized prospective bi-centric single-arm phase II clinical trial of 177Lu-PSMA-617 molecular radiotherapy in patients with progressive metastatic castrate-resistant prostate cancer (mCRPC) conducted at University of California Los Angeles (USA) and Excel Diagnostics & Nuclear Oncology Center (Houston, TX, USA) (NCT03042312). The study was investigator-initiated under an investigational new drug approval protocol (IND#133661) with authorization of charging for investigational drug (cost-recovery, Title 21 CFR 312.8). We report here the post-hoc analysis of overall survival (OS) in a single-study site cohort (UCLA). Methods: Patients with progressive mCRPC (biochemical, radiographic, or clinical) after ≥1 novel androgen axis drug (NAAD), either chemotherapy (CTX) naïve or post-CTX, with sufficient bone marrow reserve, normal kidney function, and sufficient PSMA-target expression by PET were eligible. Patients received up to 4 cycles of 177Lu-PSMA-617 every 8±1 weeks and were randomized into 2 treatment activities groups (6.0 or 7.4 GBq). Efficacy was defined as serum PSA decline of ≥50% from baseline and served as primary endpoint (hypothesis: ≥40% of responders after 2 cycles). Results: 43 patients were randomized to the 6.0 GBq (n= 14) and 7.4 GBq (n=29) treatment arms. 11/43 (26%) were CTX naïve while 10/43 (23%), 12/43 (28%), 5/43 (12%) and 5/43 (12%) had received 1, 2, 3 or 4 CTX regimens. Median baseline PSA was 29.2 ng/ml (mean 228.8, range 0.5-2082.6). 21/43 (49%) completed 4 cycles of 177Lu-PSMA-617 whereas 4/43 (9%), 13/43 (30%) and 5/43 (12%) underwent 1, 2 and 3 cycles. PSA decline of ≥50% was observed in 11/43 of patients (26%) after 2 cycles and in 16/43 (37%) at any time (best PSA response). 9/43 (21%) had a PSA decline of ≥90% and 23/43 (53%) had any PSA decline (>0%). After a median follow-up of 19.5 months the median OS was 14.8, 15.7 and 13.5 months in the whole cohort, the 6.0 GBq and 7.4 GBq treatment arms, respectively (p=0.68). Patients showing a PSA decline of ≥50% after 2 cycles and at any time had a longer OS: median 20.1 months vs. 13.6 (p=0.091) and 20.1 vs. 11.6 (p=0.002), respectively. Conclusions: In this post-hoc analysis of a single-site cohort of 43 patients included in a prospective phase II trial the median OS after 177Lu-PSMA-617 molecular radiotherapy in patients with progressive mCRPC was 14.8 months. There was no difference of efficacy between the 6.0 GBq and 7.4 GBq treatment arms. Clinical trial information: NCT03042312 .

Prognostic markers for overall survival and outcome to LuPSMA radionuclide treatment in patients with metastatic castration-resistant prostate cancer

5548

Background: The aim of this international multicenter retrospective analysis was to identify prognostic markers for the clinical outcome in late-stage mCRPC patients treated with 177Lutetium-prostate-specific membrane antigen (LuPSMA) radionuclide treatment. Methods: Patients with progressive mCRPC treated with LuPSMA at six centers in Germany, USA, and Australia were considered for inclusion. Eligible patients had 24 predefined, pretherapeutic covariates (demographics, prior mCRPC treatments, and PSMA PET/CT derived parameters) and survival data available. Endpoints included overall survival (OS) and PSA progression-free survival (PSA-PFS). Covariates were tested using univariate and mulitvariate proportional hazards regression Cox models. Results: 267/414 (64%) patients met inclusion criteria and were analyzed. 113 patients participated in clinical trials (ACTRN12615000912583, NCT03042312), while 154 were enrolled in compassionate-access programs. After a median follow-up of 22.5 months, median OS was 13.0 months (95%CI 11.6-14.4); 83% of the patients died. Median PSA-PFS was 4.0 months (95%CI 3.2-4.7). In the multivariate analysis, factors associated with shorter OS were: shorter time since diagnosis of prostate cancer (HR=2.04; p=0.002), lower number of prior systemic therapies (≤3; HR=1.56; p=0.006), prior exposure to chemotherapy (HR=1.42; p=0.05), lower hemoglobin levels (HR=1.13; p=0.002), higher number of lesions (≥20: HR=1.53; p=0.009), multiple sites of metastases (bone/LN only vs. bone + LN; HR=1.39; p=0.03) and visceral involvement (M1c) (HR=1.45; p=0.01). Factors associated with longer PSA-PFS were: longer time since diagnosis of prostate cancer (HR=0.44; p<0.001), higher hemoglobin levels (HR=0.32; p=0.03), presence of pelvic lymph nodes (LN) metastasis (N1) (HR=0.68; p=0.01), no distant lymph node metastases (M1a) (HR=0.66; p=0.01), no skeleton involvement (HR=0.44; p=0.01), no visceral metastases (M1c) (HR=0.51; p<0.001), higher PSMA-positive tumor volume (HR=0.87; p=0.04), and higher SUVmean (HR=0.94; p=0.002). Conclusions: This retrospective analysis identified prognostic factors for survival and treatment response to LuPSMA. Along with the conventional risk factors in mCRPC, PSMA PET/CT can be a useful tool for stratifying patients and guide patient’s selection for LuPSMA radionuclide treatment.

Accuracy of 68Ga-PSMA-11 for pelvic nodal metastasis detection prior to radical prostatectomy and pelvic lymph node dissection: A multicenter prospective phase III imaging study

5502

Background: To determine the accuracy of 68Ga-PSMA-11 PET for the detection of pelvic nodal metastases (N1) compared to histopathology at time of radical prostatectomy (RP). Methods: This is a prospective multicenter single-arm open-label phase 3 imaging trial. Patients with intermediate to high risk prostate cancer (PCa) considered for RP with lymph node dissection (PLND) were enrolled at the University of California, Los Angeles (UCLA) and at the San Francisco (UCSF) (NCT03368547, NCT02611882, NCT02919111), and underwent one 68Ga-PSMA-11 PET. The primary endpoint was the sensitivity (Se) and specificity (Sp) of 68Ga-PSMA-11 PET for the N1 detection compared to PLND histopathology (reference-standard) on a per patient basis using nodal region-based correlation. Each scan was read by three blinded independent central readers (BICR). Consensus was based on majority rule. Results: From December 2015 to August 2019, 633 patients underwent one 68Ga-PSMA-11 PET for primary staging, and 277/633 (44%) subsequently underwent RP and PLND. The median initial PSA was 11.1 [0.04-147]. 75/277 patients (27%) had N1 disease per histopathology. Using a regional based analysis, Se, Sp, positive predictive value (PPV) and negative predictive value (NPV) for N1 detection was 0.40 [0.34, 0.46], 0.95 [0.92, 0.97], 0.75 [0.70, 0.80], 0.81 [0.76, 0.85], respectively. Se was higher for patients with higher PSA: 0.29 [0.24, 0.35] for PSA < 11 ng/ml versus 0.48 [0.42, 0.54] for PSA > 11. Se was higher when the nodes were larger: 0.30 [0.25, 0.36] for nodes < 10 mm versus 0.68 [0.63, 0.74] for nodes > 10. The average node size in true positive patients was 10 mm versus 4 mm in false negative patients. Conclusions: In intermediate to high risk PCa patients who underwent RP and PLND, 68Ga-PSMA-11 PET detected pelvic nodal metastases with a sensitivity of 0.40 and a specificity of 0.95. Higher PSAs and larger node size correlated with increased sensitivity. Clinical trial information: NCT03368547, NCT02611882, NCT02919111 .

Efficacy and safety of 177Lu-PSMA radionuclide treatment in patients with diffuse bone marrow involvement: A multicenter retrospective study

e17543

Background: 177Lu-labelled prostate-specific membrane antigen (LuPSMA) radionuclide therapy of metastatic castration-resistant prostate cancer (mCRPC) is currently under investigation in phase III trial (VISION). However, patients with diffuse bone involvement, diagnosed with a superscan by bone scintigraphy at baseline, were excluded due to lack of efficacy and safety data. We therefore aimed to investigate the feasibility of LuPSMA in patients with diffuse bone marrow involvement on baseline PSMA-targeted PET/CT. Methods: Patients with progressive mCRPC treated with LuPSMA at six centers in Germany, USA and Australia were considered for inclusion.Eligible patients had 50% or greater bone involvement of the axial skeleton on the baseline PSMA PET. The primary endpoints were PSA response (PCWG3), toxicity (CTCAE v4.02), and overall survival (OS). Secondary endpoints included quality of life (assessed with Brief Pain Inventory-Short Form questionnaires) and radiological response (as measured by CT using RECIST 1.1). Results: 43 of 352 (12%) screened patients met inclusion criteria and were retrospectively analyzed. Median baseline PSA was 1000 (IQR 431-2151) ng/ml. PSA decline ≥50% was achieved in 26/43 (65%) patients, while median PSA progression-free survival was 4.8 (95%CI 2.4–7.1) mo. 15/42 (36%) evaluable patients exhibited pain progression with a median time-to-pain progression of 8.3 (95%CI 5.4–11.3) mo. After a median follow-up of 18.9 mo, median OS was 11.6 (95%CI 8.8-14.3) mo. Objective response in nodal or visceral disease was reported in 7/18 (39%) patients with evaluable target lesions on CT. Grade 3/4 anemia, thrombocytopenia and neutropenia occurred in 9/43 (21%), 10/43 (23%) and 3/43 (8%) patients, respectively. Of note, all patients had grade 1 anemia at baseline, with a median hemoglobin of 9.6 g/dl. 2/43 (5%) patients experienced an adverse event that required a reduction to the LuPSMA activity beginning with the third cycle. Conclusions: Patients with diffuse bone marrow involvement demonstrate similar LuPSMA efficacy and safety when compared to phase II evidence. Acceptable safety outcomes do not support exclusion of patients with a superscan from future LuPSMA treatment protocols.

Treatment-related changes in neuroendocrine tumors as assessed by textural features derived from 68Ga-DOTATOC PET/MRI with simultaneous acquisition of apparent diffusion coefficient

Background

Neuroendocrine tumors (NETs) frequently overexpress somatostatin receptors (SSTRs), which is the molecular basis for ⁶⁸Ga-DOTATOC positron-emission tomography (PET) and radiopeptide therapy (PRRT). However, SSTR expression fluctuates and can be subject to treatment-related changes. The aim of this retrospective study was to assess, which changes in PET and apparent diffusion coefficient (ADC) occur for different treatments and if pre-therapeutic ⁶⁸Ga-DOTATOC-PET/MRI was able to predict treatment response to PRRT.

Methods

Patients with histopathologically confirmed NET, at least one liver metastasis > 1 cm and at least two ⁶⁸Ga-DOTATOC-PET/MRI including ADC maps were eligible. ⁶⁸Ga-DOTATOC-PET/MRI of up to 5 liver lesions per patients was subsequently analyzed. Extracted features comprise conventional PET parameters, such as maximum and mean standardized uptake value (SUVmax and SUVmean) and ADC values. Furthermore, textural features (TFs) from both modalities were extracted. In patients with multiple ⁶⁸Ga-DOTATOC-PET/MRI a pair of 2 scans each was analyzed separately and the parameter changes between both scans calculated. The same image analysis was performed in patients with ⁶⁸Ga-DOTATOC-PET/MRI before PRRT. Differences in PET and ADC maps parameters between PRRT-responders and non-responders were compared using Mann-Whitney test to test differences among groups for statistical significance.

Results

29 pairs of ⁶⁸Ga-DOTATOC-PET/MRI scans of 18 patients were eligible for the assessment of treatment-related changes. In 12 cases patients were treated with somatostatin analogues between scans, in 9 cases with PRRT and in 2 cases each patients received local treatment, chemotherapy and sunitinib. Treatment responders showed a statistically significant decrease in lesion volume and a borderline significant decrease in entropy on ADC maps when compared to non-responders. Patients treated with standalone SSA showed a borderline significant decrease in mean and maximum ADC, compared to patients treated with PRRT. No parameters were able to predict treatment response to PRRT on pre-therapeutic ⁶⁸Ga-DOTATOC-PET/MRI.

Conclusions

Patients responding to current treatment showed a statistically significant decrease in lesion volume on ADC maps and a borderline significant decrease in entropy. No statistically significant changes in PET parameters were observed. No PET or ADC maps parameters predicted treatment response to PRRT. However, the sample size of this preliminary study is small and further research needed.

Mapping Prostate Cancer Lesions Before and After Unsuccessful Salvage Lymph Node Dissection Using Repeat PSMA PET

The aim of this study was to analyze patterns of persistent versus recurrent or new PET lesions in a selected patient cohort with prostate-specific antigen (PSA) persistence after salvage lymph node dissection (SLND) and pre-procedure and post-procedure prostate-specific membrane antigen (PSMA) ligand PET. Methods: Sixteen patients were included in this multicenter study. The inclusion criteria were PSMA PET performed for biochemical recurrence before SLND (pre-SLND PET) and repeat PSMA PET performed for a persistently elevated PSA level (≥0.1 ng/mL) at least 6 wk after SLND (post-SLND PET). Image analysis was performed by 3 independent nuclear medicine physicians applying the molecular imaging TNM system PROMISE. Lesions were confirmed by histopathology, presence on correlative CT/MRI/bone scanning, or PSA response after focal therapy. Results: Post-SLND PET identified prostate cancer lesions in 88% (14/16) of patients with PSA persistence after SLND. Median PSA was 1.2 ng/mL (interquartile range, 0.6-2.8 ng/mL). Disease was confined to the pelvis in 56% of patients (9/16), and most of these men had common iliac (6/16, 38%) and internal iliac lymph node metastases (6/16, 38%). Extrapelvic disease was detected in 31% of patients (5/16). In pre- and post-SLND PET comparison, 10 of 16 had at least one lesion already detected at baseline (63% PET persistence), 4 of 16 had new lesions only (25% PET recurrence), and 2 had no disease on post-SLND PET. All validated regions (11 regions in 9 patients) were true-positive. Nine of 14 (64%) patients underwent repeat local therapies after SLND (7/14 radiotherapy, 2/14 surgery). Conclusion: SLND of pelvic nodal metastases was often not complete according to PSMA PET. About two thirds of patients had PET-positive nodal disease after SLND already seen on pre-SLND PSMA PET. Notably, about one quarter of patients had new lesions, not detected by presurgical PSMA PET.

EANM procedure guidelines for radionuclide therapy with 177Lu-labelled PSMA-ligands (177Lu-PSMA-RLT)

Prostate-specific membrane antigen (PSMA) is expressed in most prostate cancers and can be identified by PSMA-ligand imaging, which has already become clinically accepted in several countries in- and outside Europe. PSMA-directed radioligand therapy (PSMA-RLT) with Lutetium-177 (¹⁷⁷Lu-PSMA) is currently undergoing clinical validation. Retrospective observational data have documented favourable safety and striking clinical responses. Recent results from a prospective clinical trial (phase II) have been published confirming high response rates, low toxicity and reduction of pain in metastatic castration-resistant prostate cancer (mCRPC) patients who had progressed after conventional treatments. Such patients typically survive for periods less than 1.5 years. This has led some facilities to adopt compassionate or unproven use of this therapy, even in the absence of validation within a randomised-controlled trial. As a result, a consistent body of evidence exists to support efficacy and safety data of this treatment. The purpose of this guideline is to assist nuclear medicine specialists to deliver PSMA-RLT as an "unproven intervention in clinical practice", in accordance with the best currently available knowledge.

Salvage PRRT with 177Lu-DOTA-octreotate in extensively pretreated patients with metastatic neuroendocrine tumor (NET): dosimetry, toxicity, efficacy, and survival

Background

NETTER-1 trial demonstrated high efficacy and low toxicity of four cycles of Peptide Receptor Radionuclide Therapy (PRRT) in patients with metastasized NET. The present study evaluates the outcome of further PRRT cycles in the so called salvage setting in patients after initial response to four therapy cycles and later progression.

Methods

Thirty five patients (pat.) (25 male, 10 female, 63 ± 9 years) with progressive, metastasized NET (23 small intestinal, 5 lung, 4 CUP, 1 rectal, 1 gastric and 1 paraganglioma) were included. All patients previously received 4 PRRT cycles with ¹⁷⁷Lu-DOTATATE and showed initial response. SPECT based dosimetry was applied to determine kidney and tumor doses. Therapy response was evaluated using ⁶⁸Ga-DOTATATE PET/CT (with high dose CT), CT alone or MRI (RECIST 1.1), toxicity was defined using CTCAE 5.0 criteria. ^99mTc99-MAG3 scintigraphy was used to assess potential renal tubular damage. Progression free survival (PFS) and Overall survival (OS) analysis was performed with the Kaplan-Meier-method.

Results

The median PFS after initial PRRT was 33 months (95% CI: 30–36). The mean cumulative dose for including salvage PRRT was 44 GBq (range 33.5–47). One pat. (2.9%) showed grade 3 hematotoxicity. Kidney dosimetry revealed a mean cumulative kidney dose after a median of 6 PRRT cycles of 23.8 Gy. No grade 3 / 4 nephrotoxicity or relevant decrease in renal function was observed. Follow-up imaging was available in 32 patients after salvage therapy. Best response according to RECIST 1.1. was PR in one patient (3.1%), SD in 26 patients (81.3%) and PD in 5 patients (15.6%). PFS after salvage therapy was 6 months (95% CI: 0–16; 8 patients censored). Mean OS after initial PRRT was 105 months (95% CI: 92–119) and 51 months (95% CI: 41–61) after start of salvage therapy. Median OS was not reached within a follow-up of 71 months after initial PRRT and 25 months after start of salvage PRRT, respectively.

Conclusions

Salvage therapy with ¹⁷⁷Lu-DOTATATE is safe and effective even in patients with extensive previous multimodal therapies during disease progression and represents a feasible and valuable therapy option for progressive NET.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-6000-y) contains supplementary material, which is available to authorized users.