At the heart of the debate is metaiodobenzylguanidine, known almost universally in the field as MIBG. For roughly four decades, radiolabeled MIBG has been the workhorse of neuroblastoma imaging. The molecule is a norepinephrine analog that is taken up by cells expressing the norepinephrine transporter, a protein abundantly displayed on neuroblastoma cells. When labeled with iodine-123, a gamma-emitting radionuclide, MIBG allows physicians to map tumor deposits across the body using single-photon emission computed tomography, or SPECT. The same biology underpins a second use: when labeled with iodine-131, a beta-emitting isotope, MIBG becomes both a diagnostic probe and a therapeutic agent, delivering targeted radiation to tumor cells that absorb it. This dual identity makes MIBG unusually important, because the tracer used to find the disease is also the tracer used to treat it.

The challenger in this story is a fluorinated cousin of MIBG called 18F-metafluorobenzylguanidine, abbreviated mFBG. Chemically, the two molecules are close relatives: both are guanidine derivatives that hijack the norepinephrine transporter to accumulate inside neuroendocrine and neuroblastoma cells. The critical difference lies in the radioactive label. Fluorine-18 is a positron emitter, which means it enables imaging with positron emission tomography rather than SPECT. PET detectors register the annihilation photons produced when positrons meet electrons, yielding images with substantially higher spatial resolution, better contrast, and more accurate quantification than conventional gamma-camera imaging. Fluorine-18 also has a physical half-life of about 110 minutes, compared with roughly 13 hours for iodine-123, which affects logistics, radiation dosimetry, and the practicalities of distribution to hospitals without an on-site cyclotron.

The case for mFBG gained momentum through a series of clinical studies. A first-in-human biodistribution and dosimetry study published in the Journal of Nuclear Medicine in 2018 by Nadia Pandit-Taskar and colleagues evaluated 18F-meta-fluorobenzylguanidine in patients with neuroendocrine malignancies and established its safety profile and radiation dose characteristics. More recently, in 2025, the same group published a lesion-based analysis of mFBG PET imaging specifically in neuroblastoma, examining how the tracer performs at the level of individual tumor deposits. These investigations suggested that the fluorinated agent could detect disease with a sensitivity and image quality that might rival or exceed the established iodine-123 compound, while offering the quantification advantages inherent to PET.

Against this backdrop, Albano, Bertagna, Piccardo, Fiz, and Treglia published a systematic review and meta-analysis in Pediatric Radiology in 2026 that directly compared 18F-mFBG with 123I-MIBG in neuroblastoma. Meta-analysis is a statistical technique that pools the results of multiple independent studies to extract a more precise estimate of a diagnostic test’s performance than any single trial can provide. Their head-to-head synthesis, drawing on the accumulated published evidence, represented one of the first attempts to formally quantify whether the new fluorinated tracer truly outperforms the old guard. The work quickly became a reference point in the field, and, as is often the case when a new technology threatens to displace an entrenched standard, it did not go unchallenged.

The challenge came from Yadgarov, Antonevskaya, and Likar, whose reply, published on 17 August 2026, took issue with aspects of the meta-analysis and with the broader inference that mFBG PET/CT is ready to supplant MIBG scintigraphy in routine clinical practice. Their critique, and the response from Albano and Treglia published two weeks later, exemplifies a familiar pattern in diagnostic imaging research. When a new tracer with superior physics arrives, enthusiasm can outrun the evidence. Questions that matter in this transition include whether the studies being compared enrolled comparable patient populations, whether the reference standards used to confirm true disease status were equivalent, whether lesion detection rates were analyzed per patient or per lesion, and whether the dosimetric implications of switching tracers have been fully characterized in children rather than extrapolated from adult neuroendocrine tumor cohorts.

These methodological points are not pedantic. In pediatric neuroblastoma, imaging findings directly determine risk stratification and therapy. The International Neuroblastoma Risk Group staging system and the treatment protocols built upon it rely on MIBG avidity as a defining biological feature of the disease. A child whose tumor takes up MIBG is eligible for 131I-MIBG targeted radiotherapy if standard treatment fails; a tumor that is MIBG-negative generally is not. If mFBG were to replace MIBG for diagnostic imaging, the field would need to confirm that the new tracer identifies the same transporter-expressing cell population, so that diagnostic avidity continues to predict therapeutic avidity. A tracer that lights up more lesions on a prettier image is not automatically a better tracer if it changes the relationship between what is seen and what can be treated.

The dosimetry question adds another layer of complexity, particularly acute in pediatrics. Children are more radiosensitive than adults, and every imaging examination must be justified against the radiation burden it imposes. Fluorine-18’s short half-life means the administered activity clears quickly, which can reduce the effective dose compared with longer-lived isotopes, but the full-body biodistribution of mFBG in children, including uptake in organs such as the myocardium, liver, and salivary glands, must be mapped carefully. The 2018 first-in-human study provided adult dosimetry data, and the 2025 lesion analysis extended the clinical picture, but pediatric-specific dosimetry remains an area where reviewers and regulators rightly demand rigor. Any claim that one tracer is safer than another must rest on measured dose coefficients in the population actually being imaged, not on assumptions carried across age groups and disease types.

There is also a practical economics dimension that the scientific exchange implicitly raises. Iodine-123 MIBG is available through established radiopharmacy supply chains in many countries, whereas 18F-mFBG requires either a local cyclotron and radiochemistry capability or a regional distribution network, infrastructure that many pediatric oncology centers, particularly in lower-resource settings, do not possess. Conversely, the higher spatial resolution of PET can change management by revealing lesions that SPECT misses, potentially altering surgical planning and response assessment. Whether that incremental diagnostic yield justifies the infrastructure investment is precisely the kind of question that meta-analyses, correspondence, and rebuttals are meant to adjudicate in public, with the reasoning visible to clinicians who must make decisions for individual children.

What the Albano and Treglia reply ultimately illustrates is that the transition from 123I-MIBG to 18F-mFBG in neuroblastoma will be decided not by any single study but by the cumulative weight of carefully scrutinized evidence. The authors of both the original meta-analysis and the critique agree on the fundamentals: mFBG is a promising tracer with genuine physical advantages, and the emerging literature supports its diagnostic potential. Where they differ is in how strongly the current evidence licenses a change in practice. That disagreement, aired transparently in the correspondence columns of Pediatric Radiology, is how the field protects itself against both premature adoption and unwarranted delay. For the children whose scans will guide their treatment in the coming years, the outcome of this technical argument is anything but academic; it will help determine which images their doctors trust, which therapies they become eligible for, and how precisely their disease can be measured from diagnosis through remission.

Subject of Research: Comparison of 18F-metafluorobenzylguanidine PET/CT and 123I-MIBG scintigraphy for neuroblastoma imaging

Article Title: Reply to:18F-Metafluorobenzylguanidine positron emission tomography/computed tomography in neuroblastoma

Article References: Albano, D., & Treglia, G. (2026). Reply to:18F-Metafluorobenzylguanidine positron emission tomography/computed tomography in neuroblastoma. Pediatric Radiology. https://doi.org/10.1007/s00247-026-06769-x

Image Credits: AI Generated

DOI: 10.1007/s00247-026-06769-x

Keywords: neuroblastoma, 18F-mFBG, 123I-MIBG, PET/CT, SPECT, pediatric radiology, nuclear medicine, meta-analysis, norepinephrine transporter, dosimetry, molecular imaging, Reply

The study, published in the European Journal of Nuclear Medicine and Molecular Imaging by Xiaoya Wang, Keyu Zhang and colleagues at Beijing Friendship Hospital, Capital Medical University, focused on a radiotracer called ¹⁸F-meta-fluorobenzylguanidine, or ¹⁸F-MFBG. The tracer is a fluorine-18-labeled analogue of the long-standing imaging agent MIBG, and it exploits a quirk of neuroblastoma biology: these tumors arise from the sympathetic nervous system and, like their healthy counterparts, express the norepinephrine transporter on their cell surfaces. When injected into a patient, ¹⁸F-MFBG travels through the bloodstream and is actively pumped into tumor cells by this transporter, lighting up the tumor on a PET scan with a specificity that few other tracers can match.

The researchers enrolled 42 pediatric patients, all with histologically confirmed diagnoses established after the scan: 23 with neuroblastoma and 19 with ganglioneuroblastoma, the intermediate form of the disease that contains a mixture of primitive neuroblasts and more mature ganglion cells. Each child underwent ¹⁸F-MFBG PET/CT before any treatment began, allowing the team to extract quantitative imaging parameters from the primary tumors without the confounding effects of chemotherapy or surgery. Alongside the imaging data, the team compiled clinical variables including age at diagnosis, the presence of bone metastases, and genetic findings such as the 11q23 deletion, a chromosomal abnormality associated with aggressive disease.

The quantitative analysis went well beyond simple visual inspection. The team measured standard uptake values, including SUVmax and SUVmean, which reflect how avidly the tumor traps the tracer, as well as tumor-to-background ratios that normalize uptake against surrounding tissue. They also computed texture-based features such as AUC-CSH, a measure derived from the histogram of voxel intensities that captures the heterogeneity of tracer distribution within the tumor, and TL-hNET, an estimate of total lesion norepinephrine transporter expression that integrates uptake intensity with metabolic tumor volume. Six of these parameters, including SUVmax, SUVmean, TBRmean, TBRmax, AUC-CSH and TL-hNET, differed significantly between neuroblastoma and ganglioneuroblastoma, confirming that the two tumor types handle the tracer in measurably different ways.

Those differences make biological sense. Neuroblastoma, composed of densely packed, primitive neuroblasts, tends to express the norepinephrine transporter at high levels and take up MFBG avidly. Ganglioneuroblastoma, with its greater proportion of mature ganglion cells and Schwannian stroma, typically shows weaker transporter activity and therefore dimmer signal on the scan. But the researchers also encountered a familiar statistical obstacle: the imaging parameters were heavily intercorrelated, with variance inflation factors exceeding 10, meaning they carried largely redundant information. Rather than stuffing all of them into a model and risking overfitting, the team selected SUVmax as the single representative imaging variable for multivariable analysis, a disciplined choice given the modest sample size.

To handle the small cohort without producing unstable estimates, the researchers turned to Firth logistic regression, a penalized form of logistic regression specifically designed for situations where events are rare or predictors are numerous relative to the sample. In the final multivariable model, two variables emerged as independent predictors of neuroblastoma: SUVmax, with an odds ratio of 8.665, meaning each increment in tracer uptake sharply raised the odds of malignancy, and younger age, with an odds ratio of 0.676, reflecting the well-established fact that neuroblastoma tends to strike earlier in life than its better-differentiated counterpart. Bone metastasis showed a strong trend toward independent association, with an odds ratio of 11.753 and a p-value of 0.050, hovering just at the threshold of conventional statistical significance.

With these predictors in hand, the team constructed and compared three diagnostic models: an imaging-only model using SUVmax alone, a clinical model combining age and bone metastasis, and an integrated model merging all three variables. The results told a clear story of incremental value. The imaging-only model achieved an area under the ROC curve of 0.810, the clinical model 0.787, and the integrated model 0.856, with a 95 percent confidence interval of 0.737 to 0.975. While the differences in AUC alone showed only a trend toward significance on the DeLong test, two complementary statistical tools provided firmer support. Bootstrap validation across 2,000 resamples confirmed the stability of the estimates, and integrated discrimination improvement analysis showed that the combined model significantly outperformed both alternatives, with an IDI of 0.122 against the imaging-only model and 0.083 against the clinical model, both statistically significant.

The clinical implications of these numbers are worth unpacking. An AUC of 0.856 means the integrated model discriminates between the two tumor types correctly in roughly 86 percent of paired comparisons, a level of performance that, if confirmed in larger cohorts, could meaningfully change the diagnostic pathway for children with neuroblastic tumors. A child whose scan shows high SUVmax, who is very young, and who has bone metastases would be flagged as high-risk for neuroblastoma, potentially accelerating the decision to begin treatment. Conversely, a child with low tracer uptake, older age and no skeletal spread could be triaged toward a more watchful approach, sparing families the physical and emotional toll of an unnecessary biopsy in a location where complications could be severe.

The study’s authors are appropriately measured in their conclusions, framing the work as a preliminary hypothesis-generating effort that awaits rigorous external validation in larger, multicenter cohorts. That caution is warranted. Forty-two patients is a small sample, and the model was developed and evaluated within the same dataset, a design that inflates apparent performance compared with true out-of-sample prediction. The field of radiomics and imaging-based diagnostics is littered with promising single-center studies that failed to replicate, a problem that has prompted formal criteria for translating such models into clinically useful tests. The Beijing team’s transparent reporting of confidence intervals, bootstrap validation and reclassification statistics suggests an awareness of these pitfalls, but the ultimate test will be independent replication.

Still, the direction of travel is unmistakable. ¹⁸F-MFBG offers practical advantages over the iodine-123-labeled MIBG that has dominated neuroblastoma imaging for decades, including superior spatial resolution, the ability to perform same-day imaging, and no requirement for thyroid blockade or iodine saturation protocols. Combined with quantitative texture analysis and thoughtful integration of clinical and genetic risk factors, it is becoming a probe not just of where a tumor is, but of what it fundamentally is. For a disease whose treatment intensity spans the full spectrum from observation to myeloablative therapy, that kind of molecular discrimination, delivered through a simple scan rather than a surgical needle, could reshape pediatric cancer care. The next step, larger multicenter trials, will determine whether this preliminary signal hardens into a standard of practice.

Subject of Research: Noninvasive differentiation of neuroblastoma from ganglioneuroblastoma using ¹⁸F-MFBG PET/CT imaging parameters and clinical factors

Article Title: Diagnostic performance of multiparametric model integrating ¹⁸F-MFBG PET/CT imaging parameters and clinical factors for differentiating neuroblastoma from ganglioneuroblastoma: a preliminary study

Article References: Wang, X., Zhang, K., Kan, Y., Wang, W., & Yang, J. (2026). Diagnostic performance of multiparametric model integrating ¹⁸F-MFBG PET/CT imaging parameters and clinical factors for differentiating neuroblastoma from ganglioneuroblastoma: a preliminary study. European Journal of Nuclear Medicine and Molecular Imaging. https://doi.org/10.1007/s00259-026-08185-7

Image Credits: AI Generated

DOI: 10.1007/s00259-026-08185-7

Keywords: neuroblastoma, ganglioneuroblastoma, 18F-MFBG, PET/CT, pediatric oncology, molecular imaging, SUVmax, diagnostic model, norepinephrine transporter, logistic regression, radiomics, biopsy