Purpose: We aimed to determine the impact of fibroblast activation protein inhibitor (FAPI)–directed molecular imaging on staging and therapeutic management in patients affected with digestive system tumors when compared with guideline-compatible imaging (GCI). Patients and Methods: Thirty-two patients with tumors of the digestive system were included: colon adenocarcinoma, 2/32 (6.3%); hepatocellular carcinoma (HCC), 6/32 (18.8%); pancreatic duct adenocarcinoma (PDAC), 6/32 (18.8%), and gastroenteropancreatic neuroendocrine neoplasms, 18/32 (56.3%). All patients underwent GCI and ⁶⁸Ga-FAPI-04 PET/CT within median 4 days. Staging outcomes and subsequent treatment decisions were compared between GCI and ⁶⁸Ga-FAPI-04 PET/CT. Results: Compared with GCI, ⁶⁸Ga-FAPI-04 PET/CT led to staging changes in 15/32 patients (46.9%). Among those, downstaging was recorded in 3/15 cases (20.0%) and upstaging in the remaining 12/15 patients (HCC, 4/12 [33.3%]; PDAC, 4/12 [33.3%]; neuroendocrine neoplasms, 3/12 [25%]; colon adenocarcinoma, 1/12 [8.3%]). Therapeutic management was impacted in 8/32 patients (25.0%), including 4 instances of major and 4 instances of minor therapeutic changes. The highest proportion of treatment modifications was observed in patients diagnosed with PDAC and HCC in 6/8 (75%). Conclusions: In patients affected with digestive system tumors, ⁶⁸Ga-FAPI-04 PET/CT resulted in staging changes in more than 46% and therapeutic modifications in 25% of the cases, in particular in patients with HCC and PDAC. In clinical routine, such findings may favor a more widespread adoption of FAP-directed imaging in those tumor types.

Background: Two randomized clinical trials demonstrated the efficacy of prostate-specific membrane antigen (PSMA) radioligand therapy (PSMA RLT) in metastatic castration-resistant prostate cancer (mCRPC). While the VISION trial used criteria within PSMA PET/CT for inclusion, the TheraP trial used dual tracer imaging including FDG PET/CT. Therefore, we investigated whether the application of the VISION criteria leads to a benefit in overall survival (OS) or progression-free survival (PFS) for men with mCRPC after PSMA RLT. Methods: Thirty-five men with mCRPC who had received PSMA RLT as a last-line option and who had undergone pretherapeutic imaging with FDG and [⁶⁸Ga]Ga-PSMA I&T or [¹⁸F]PSMA-1007 were studied. Therapeutic eligibility was retrospectively evaluated using the VISION and TheraP study criteria. Results: 26 of 35 (74%) treated patients fulfilled the VISION criteria (= VISION+) and only 17 of 35 (49%) fulfilled the TheraP criteria (= TheraP+). Significantly reduced OS and PFS after PSMA RLT was observed in patients rated VISION− compared to VISION+ (OS: VISION−: 3 vs. VISION+: 12 months, hazard ratio (HR) 3.1, 95% confidence interval (CI) 1.0–9.1, p < 0.01; PFS: VISION−: 1 vs. VISION+: 5 months, HR 2.7, 95% CI 1.0–7.8, p < 0.01). For patients rated TheraP−, no significant difference in OS but in PFS was observed compared to TheraP+ patients (OS: TheraP−: 5.5 vs. TheraP+: 11 months, HR 1.6, 95% CI 0.8–3.3, p = 0.2; PFS: TheraP−: 1 vs. TheraP+: 6 months, HR 2.2, 95% CI 1.0–4.5, p < 0.01). Conclusion: Retrospective application of the inclusion criteria of the VISION study leads to a benefit in OS and PFS after PSMA RL, whereas TheraP criteria appear to be too strict in patients with end-stage prostate cancer. Thus, performing PSMA PET/CT including a contrast-enhanced CT as proposed in the VISION trial might be sufficient for treatment eligibility of end-stage prostate cancer patients.

We aimed to quantitatively investigate the prognostic value of PET-based biomarkers on [¹⁸F]FDG and [⁶⁸Ga]Ga-fibroblast activation protein inhibitor (FAPI)-04 PET/CT in patients with highly aggressive neuroendocrine neoplasms (NENs) and to compare the visually assessed differences in uptake on both examinations with progression-free survival (PFS). Methods: In this single-center retrospective analysis, 20 patients with high-grade NENs had undergone [¹⁸F]FDG and [⁶⁸Ga]Ga-FAPI-04 PET. Both PET scans were visually compared, and the presence of [¹⁸F]FDG-positive, [⁶⁸Ga]Ga-FAPI-04–negative (FDG+/FAPI−) lesions was noted. In addition, we assessed maximum, peak, and mean SUV; tumor volume (TV); and total lesion uptake (TLU = TV × SUV_mean) for both radiotracers using a 40% lesion-based threshold. The results of quantitative and visual analysis were correlated with PFS using log-rank analysis or univariate Cox regression. PFS was defined radiographically using RECIST 1.1., clinically using signs of disease progression, or as death. Results: Most primary tumors were located in the gastrointestinal tract (13/20 patients, 65%) or were cancer of unknown primary (5/20 patients, 25%). FDG+/FAPI− lesions were found in 9 of 20 patients (45%). Patients with FDG+/FAPI− lesions had a significantly decreased PFS of 4 mo, compared with 9 mo for patients without FDG+/FAPI− metastases (P = 0.0063 [log-rank test]; hazard ratio [HR], 5.637; 95% CI 1.619–26.16; P = 0.0110 [univariate Cox regression]). On univariate analysis, a significant correlation was also found between PFS and TV for both radiotracers ([¹⁸F]FDG: mean TV, 258 ± 588 cm³; HR, 1.024 [per 10 cm³]; 95% CI, 1.007–1.046; P = 0.0204) ([⁶⁸Ga]Ga-FAPI-04: mean TV, 130 ± 192 cm³; HR, 1.032 [per 10 cm³]; 95% CI, 1.001–1.062; P = 0.0277) and TLU on [¹⁸F]FDG PET (mean TLU, 1,931 ± 4,248 cm³; HR, 1.004 [per 10 cm³]; 95% CI, 1.001–1.007; P = 0.0135). Conclusion: The presence of discordant FDG+/FAPI− lesions is associated with a significantly shorter PFS, which might indicate more aggressive disease prone to early progression. Dual-tracer PET/CT of patients with highly aggressive NENs could help guide treatment decisions or identify high-risk lesions for additional local therapeutic approaches. Visual Abstract

Background: Gastro-entero-pancreatic neuroendocrine carcinomas (GEP-NECs) are an aggressive subgroup of neuroendocrine neoplasms (NENs). In patients affected with NEN, there is a growing body of evidence that increased C-X-C motif chemokine receptor (CXCR4) expression is linked to decreasing overall survival (OS) in an ex-vivo setting. Thus, we aimed to determine whether the in-vivo-derived CXCR4-directed whole-body PET signal can also determine GEP-NEC patients with shorter OS. Methods: We retrospectively included 16 patients with histologically proven GEP-NEC, who underwent CXCR4-directed PET/CT for staging and therapy planning. We assessed maximum, peak, and mean standardized uptake values as well as whole-body tumor volume (TV) and total-lesion uptake (TLU = SUVmean × TV) using a semi-automatic segmentation tool with a 50% threshold. Association of PET-based biomarkers and OS or radiographic progression-free survival (rPFS; according to RECIST 1.1 criteria) was analyzed using univariable and multivariable cox regression. Results: Median OS and rPFS was 7.5 and 7 months, respectively. A significant correlation between TV and TLU was found for OS (TV: hazard ratio (HR) 1.007 95% confidence interval (CI) 1.000–1.014, p = 0.0309; TLU: HR 1.002 95% CI 1.000–1.003, p = 0.0350) and rPFS (TV: HR 1.010 95% CI 1.002–1.021; p = 0.0275; TLU: HR 1.002 95% CI 1.000–1.004, p = 0.0329), respectively. No significant correlation with OS or rPFS was found for non-volumetric parameters (p > 0.4). TV remained a significant predictive marker for OS and rPFS in multivariable analysis (OS: HR 1.012 95%, CI 1.003–1.022, p = 0.0084; rPFS: HR 1.009, 95% CI 0.9999–1.019, p = 0.0491), whereas TLU remained only prognostic for OS (HR 1.009, 95% CI 0.9999–1.019, p = 0.0194) but narrowly failed significance for rPFS (p = 0.0559). Conclusion: In-vivo assessment of CXCR4 PET-derived volumetric parameters is predictive for outcome of patients with GEP-NEC and could be used as a risk stratification tool, which detects patients prone to early progression.

Adrenocortical carcinoma (ACC) represents a rare tumor entity with limited treatment options and usually rapid tumor progression in case of metastatic disease. As further treatment options are needed and ACC metastases are sensitive to external beam radiation, novel theranostic approaches could complement established therapeutic concepts. Recent developments focus on targeting adrenal cortex-specific enzymes like the theranostic twin [^123/131I]IMAZA that shows a good image quality and a promising therapeutic effect in selected patients. But other established molecular targets in nuclear medicine such as the C-X-C motif chemokine receptor 4 (CXCR4) could possibly enhance the therapeutic regimen as well in a subgroup of patients. The aims of this review are to give an overview of innovative radiopharmaceuticals for the treatment of ACC and to present the different molecular targets, as well as to show future perspectives for further developments since a radiopharmaceutical with a broad application range is still warranted.

High expression of prostate-specific membrane antigen (PSMA) is not limited to prostate cancer but can be found in other tumor entities, such as hepatocellular carcinoma (HCC), and could possibly be used for theranostic purposes. Our aim was to investigate the diagnostic potential of the hepatobiliary excreted radiotracer [¹⁸F]PSMA-1007 on initial staging of HCC. Methods: This prospective clinical study (NCT05547919) included 10 participants (9 men, 1 woman) with treatment-naïve, histopathologically proven PSMA-positive HCC. All participants underwent [¹⁸F]PSMA-1007 PET with unenhanced low-dose CT. All scans were analyzed visually and quantitatively. We assessed the SUV_max of the primary tumor and the SUV_mean of nonaffected liver parenchyma and calculated tumor-to-background ratios (i.e., SUV_max HCC/SUV_mean liver) for each patient. In addition, we assessed possible eligibility for PSMA-directed radiopharmaceutical therapy according to the PROMISE criteria. The presence of local lymph nodes and distant metastases was noted for [¹⁸F]PSMA-1007 PET/CT and compared with the results of contrast-enhanced CT of the trunk and MRI of the upper abdomen. Possible prognostic implications of PSMA expression on immunohistochemistry and on [¹⁸F]PSMA-1007 PET/CT were compared with progression-free survival (defined as clinical progression, radiographic progression, or death from any cause) using Cox regression. Results: [¹⁸F]PSMA-1007 PET showed high uptake in 7 of 10 patients (PROMISE score 2, n = 4; PROMISE score 3, n = 3); mediocre or missing uptake was found in 3 participants (PROMISE score 0, n = 1; PROMISE score 1, n = 2). The median tumor-to-background ratio was 2.7 (interquartile range, 2.65). [¹⁸F]PSMA-1007 PET did not reveal new distant metastatic lesions compared with contrast-enhanced CT. In 1 patient, local lymph node metastases were considered PSMA-negative despite high uptake in the primary tumor. Whether assessed ex vivo or in vivo, PSMA expression did not correlate with progression-free survival. Conclusion: [¹⁸F]PSMA-1007 can be used depict untreated HCC and shows high uptake relative to background, indicative of excellent image contrast. High tracer accumulation in 70% of the participants suggests a possible use for PSMA-directed radiopharmaceutical therapy in an end-stage setting. However, PSMA expression was not prognostic for outcome, possibly because of the small sample size. Visual Abstract