The study, led by researchers at Peking University Cancer Hospital and Institute in Beijing, enrolled forty-one patients with biopsy-proven neuroendocrine tumors. Every participant underwent both a [68Ga]Ga-DOTA-TATE PET/CT scan and a [18F]AlF-NOTA-JR11 PET/MR examination. JR11, also known as opsomat, is a somatostatin receptor antagonist rather than an agonist, a distinction that matters at the molecular level. Whereas agonist tracers bind preferentially to receptors in an active state and trigger their internalization, antagonists can bind to a larger pool of receptor conformations without activating them, potentially painting a brighter, more complete picture of receptor expression across tumor cells.

The headline result was stark. Across the study population, [18F]AlF-NOTA-JR11 PET/MR depicted 924 lesions in total, compared with 580 lesions detected by [68Ga]Ga-DOTA-TATE PET/CT, a difference the authors reported as highly significant. The advantage was driven overwhelmingly by liver metastases, where the new tracer identified 754 lesions against 405 for the incumbent. Primary tumor detection was similar between the two modalities, with 29 versus 25 primaries found, and there were no significant differences in the detection of lymph node or bone metastases. When the analysis shifted to the patient level, the pattern held: seventy-six percent of patients, thirty-one of the forty-one, had more lesions visualized on the fluorine-18 antagonist scan.

Size matters in these comparisons, and the investigators examined it carefully. The 405 liver metastases seen on both scans were significantly larger, with a median diameter of 14 millimeters, than the 349 lesions seen exclusively on [18F]AlF-NOTA-JR11, whose median diameter was just 6 millimeters. In other words, much of the incremental yield came from tiny sub-centimeter deposits, precisely the kind of small-volume disease that can alter staging, shape decisions about liver-directed therapies, and influence eligibility for peptide receptor radionuclide therapy.

Quantitative imaging metrics told an equally interesting story. Maximum standardized uptake values, the conventional measure of tracer avidity, were actually lower for [18F]AlF-NOTA-JR11 in primary tumors, liver metastases, and bone metastases compared with [68Ga]Ga-DOTA-TATE. That initially counterintuitive finding makes sense once background activity is considered. The fluorine-18 antagonist scan showed significantly lower uptake in normal tissues, and consequently a higher tumor-to-background ratio in primary tumors, lymph node metastases, and liver metastases. A dimmer background against which tumors glow brightly is often more valuable diagnostically than a raw measure of tracer accumulation, because it is contrast, not absolute intensity, that lets a radiologist resolve a lesion from its surroundings.

The chemistry behind the new tracer also carries practical significance. Gallium-68 is produced in a generator, which is convenient but constrains throughput and shelf life, since the isotope decays with a half-life of roughly sixty-eight minutes. Fluorine-18, by contrast, has a half-life of about 110 minutes and can be manufactured in cyclotron facilities with multi-center distribution, mirroring the logistics that made fluorodeoxyglucose the most widely used PET tracer in the world. The aluminum fluoride labeling method used to attach fluorine-18 to the NOTA-chelated peptide is a one-step, aqueous procedure that avoids the harsher conditions required for direct fluorination, making synthesis simpler and more amenable to routine production.

Pairing the tracer with magnetic resonance rather than computed tomography adds a second layer of advantage. MR provides superior soft-tissue contrast, particularly in the liver and abdomen, where diffusion-weighted and hepatobiliary sequences can flag lesions that CT misses. Previous work comparing PET/MR with PET/CT in oncology has shown that the combined modality can change patient management in a meaningful fraction of cases, and neuroendocrine tumors, with their hepatic predilection, stand to benefit most. The Beijing team’s design, in which the superior antagonist tracer is coupled with the superior anatomical imaging platform, deliberately stacks the deck toward maximal lesion conspicuity.

The study builds on a decade of clinical exploration of somatostatin receptor antagonists. Early proof-of-principle work demonstrated that antagonist-based imaging was feasible in humans, and subsequent head-to-head trials of gallium-68-labeled JR11 formulations against agonist tracers showed higher detection rates in metastatic, well-differentiated tumors. A parallel European study comparing a fluorine-18-labeled octreotide antagonist on PET/MR with gallium-68 DOTA-TATE PET/CT reported similar directional findings. What the new study adds is the first clinical comparison of aluminum fluoride-labeled JR11 on PET/MR, consolidating the tracer chemistry, the antagonist pharmacology, and the MR platform into a single evaluation.

Caveats remain before the findings translate into wholesale clinical practice. The cohort of forty-one patients, while adequate for a paired-lesion comparison, is modest, and the study came from a single center with radiopharmaceutical expertise in-house. The researchers did not report changes in patient management attributable to the additional lesions, so the downstream clinical impact of finding more small liver metastases, whether it prolongs survival or simply reshapes surveillance, awaits longitudinal follow-up. The authors also note that one co-author holds a position with a medical imaging company and contributed protocol optimization, although the remaining authors declared no competing interests.

Even so, the evidence positions [18F]AlF-NOTA-JR11 PET/MR as a serious contender to become the next generation of somatostatin receptor imaging. With more than four hundred additional liver lesions visualized across forty-one patients, higher tumor-to-background contrast, and a cyclotron-friendly isotope that could democratize distribution, the combination addresses the two great bottlenecks of current practice: sensitivity for small-volume hepatic disease and the supply chain constraints of gallium-68. For patients with neuroendocrine tumors, whose treatment decisions hinge on a precise map of where their disease has spread, a sharper and more widely available imaging lens could not arrive at a better time.

Subject of Research: Head-to-head comparison of fluorine-18 somatostatin receptor antagonist PET/MR and gallium-68 DOTA-TATE PET/CT for imaging neuroendocrine tumors

Article Title: Head-to-head comparison of [18F]AlF-NOTA-JR11 PET/MR and [68Ga]Ga-DOTA-TATE PET/CT in patients with neuroendocrine tumors

Article References: Head-to-head comparison of [18F]AlF-NOTA-JR11 PET/MR and [68Ga]Ga-DOTA-TATE PET/CT in patients with neuroendocrine tumors. (n.d.). https://doi.org/10.1007/s00259-026-08176-8

Image Credits: AI Generated

DOI: 10.1007/s00259-026-08176-8

Keywords: neuroendocrine tumors, PET/MR, PET/CT, somatostatin receptor antagonist, fluorine-18, gallium-68, DOTA-TATE, liver metastases, molecular imaging, nuclear medicine, tumor-to-background ratio, radiopharmaceuticals

The stakes are high. The liver is among the most frequent sites of distant spread in malignant tumors, and the number of patients with liver metastases substantially exceeds the number diagnosed with primary liver cancer. Prognosis is poor: one-year overall survival for patients with liver metastases has been reported at roughly 15 percent, compared with 24 percent for patients without such spread. Yet early and precise detection matters enormously, because options ranging from surgical resection and ablation to stereotactic radiotherapy and transarterial therapies can be curative or life-extending in selected patients. In colorectal cancer, for example, resection of limited liver metastases can push five-year survival to between 47 and 60 percent, and some patients with non-colorectal liver metastases also benefit from surgery. Accurate imaging is the gateway to those decisions.

The study, conducted at Fudan University Shanghai Cancer Center and published in Holistic Integrative Oncology, enrolled 76 patients between May 2020 and April 2023 who underwent both scans within one week. The cohort spanned 19 different malignant tumor types, comprising 65 patients with carcinomas and 11 with sarcomas, and a total of 189 liver lesions, of which 173 were ultimately confirmed as metastases through at least three months of clinical and imaging follow-up. Two experienced nuclear medicine physicians, blinded to clinical data and follow-up results, independently evaluated the images using a standardized visual scoring system supplemented by quantitative measurements.

The technical logic behind the comparison hinges on the biology of each tracer. Fluorodeoxyglucose, or FDG, is a glucose analogue that accumulates in cells with high glycolytic activity, the metabolic hallmark of many cancers. But FDG is relatively nonspecific: all living cells consume glucose, and the liver’s own background uptake is brisk, which can mask malignant lesions and inflate the false-negative rate. FAPI-04, by contrast, targets fibroblast activation protein, or FAP, a marker abundantly expressed by cancer-associated fibroblasts in the tumor stroma of a broad spectrum of malignancies. Crucially for liver imaging, FAP expression in normal hepatic parenchyma is low, producing a dark, quiet background against which bright metastatic lesions stand out with high contrast.

The results were emphatic. Across all 76 patients, the sensitivity of gallium-68 FAPI-04 PET/CT for detecting liver metastases was 94.80 percent, compared with 69.94 percent for FDG PET/CT, a difference that was highly statistically significant. Accuracy followed the same pattern, at 91.53 percent versus 70.37 percent. In the carcinoma subgroup the gap widened further: sensitivity of 97.87 percent versus 73.05 percent, and accuracy of 96.05 percent versus 74.34 percent. Even in the smaller sarcoma group, FAPI-04 achieved significantly higher sensitivity, 81.25 percent versus 56.25 percent, although accuracy did not reach statistical significance in that subset. Specificity did not differ significantly between the two tracers in any group.

Quantitative uptake measurements reinforced the visual findings. The researchers compared the maximum standardized uptake value, or SUVmax, of each lesion with the mean uptake of normal liver tissue to derive the tumor-to-background ratio, or TBR. Normal liver background activity was markedly lower with FAPI-04 than with FDG, with a mean SUV of 1.10 versus 2.61. Although overall SUVmax of metastases did not differ significantly across the whole cohort, the median TBR for FAPI-04 was more than double that of FDG, 4.60 versus 1.67, and in carcinomas both SUVmax and TBR were significantly higher for FAPI-04. In essence, even when lesion signal was similar, the quieter liver background made FAPI-04 lesions far easier to see.

The clinical consequences of that contrast were tangible. In ten patients, liver metastases were clearly positive on FAPI-04 PET/CT yet invisible to FDG PET/CT. Because distant spread determines the M stage of the TNM classification, detecting these lesions changed the staging of those patients and could alter treatment planning, from surgical candidacy and radiotherapy target delineation to systemic therapy decisions. For patients with limited, oligometastatic liver disease, more aggressive local interventions such as resection, stereotactic ablative radiotherapy, or microwave ablation may be appropriate, but only if all sites of disease are reliably identified first.

The study’s authors contextualized their findings against existing imaging standards. Magnetic resonance imaging with diffusion-weighted sequences and gadoxetic acid contrast remains the reference method for characterizing liver lesions, with pooled sensitivity of about 95 percent and specificity of about 82 percent in meta-analysis. Notably, the carcinoma subgroup performance of FAPI-04 PET/CT in this study approached those figures, making it a credible alternative for patients who cannot receive gadolinium contrast because of renal impairment or allergy. Prior smaller studies in gastrointestinal cancers and mixed tumor populations had already hinted at FAPI’s advantage, with sensitivities of 96.6 to 98.2 percent, but limited sample sizes and narrow tumor spectra left the picture incomplete. The Shanghai team’s broader cohort and explicit carcinoma-versus-sarcoma stratification add statistical weight and biological nuance.

Why did FAPI-04 perform less decisively in sarcomas? The authors point to fundamental differences in tumor origin. Carcinomas arise from epithelial tissue and typically provoke a robust stromal reaction rich in FAP-expressing fibroblasts, whereas sarcomas of mesenchymal origin display heterogeneous and often lower stromal FAP expression. That heterogeneity likely explains both the lower accuracy of 72.97 percent in sarcoma and the absence of a significant SUVmax advantage, even though the tumor-to-background ratio still favored FAPI-04 significantly. The modest specificity observed for both tracers also has recognized culprits: benign lesions such as angiomyolipoma and focal nodular hyperplasia can take up FAPI, inflammatory focal liver lesions can be FAPI-avid, and fibrotic nodules from chronic hepatitis, alcoholic liver disease, or fatty liver disease may trap the tracer, since fibroblast activation protein is a hallmark of activated hepatic stellate cells in fibrosis.

The researchers are careful to frame their conclusions as preliminary. The analysis was retrospective, most metastases were confirmed by follow-up rather than biopsy, the cohort came from a single center, and the sarcoma subgroup was small enough to invite statistical bias. Only the lesion most suspicious for malignancy per patient was generally included, which may have flattered both scanners’ performance. Still, the magnitude and consistency of FAPI-04’s advantage in carcinoma metastases, the modality where detection most often determines resectability, make a compelling case for larger prospective trials, including direct comparisons with liver MRI. If validated, a routine switch in tracer for patients at risk of hepatic spread would be a rare and consequential upgrade in an imaging workhorse that has remained largely unchanged for decades.

Subject of Research: Comparative diagnostic performance of 68Ga-FAPI-04 and 18F-FDG PET/CT imaging for detecting liver metastases from malignant tumors.

Article Title: Head-to-head comparison of the detection performance and tumor uptake of 68Ga-FAPI-04 and 18F-FDG PET/CT in liver metastases from malignant tumors of different types

Article References: Ma, G., Liu, C., Qi, M., Li, J., & Song, S. (2026). Head-to-head comparison of the detection performance and tumor uptake of 68Ga-FAPI-04 and 18F-FDG PET/CT in liver metastases from malignant tumors of different types. Holistic Integrative Oncology, 5(1), Article 74. https://doi.org/10.1007/s44178-026-00295-4

Image Credits: AI Generated

DOI: 10.1007/s44178-026-00295-4

Keywords: 68Ga-FAPI-04, 18F-FDG, PET/CT, liver metastases, molecular imaging, fibroblast activation protein, carcinoma, sarcoma, SUVmax, tumor-to-background ratio, cancer staging, nuclear medicine