18F-AlF-NOTA-octreotide outperforms 68Ga-DOTA-TATE/-NOC PET in neuroendocrine tumor patients: results from a prospective, multicenter study

Fluorine-18-labeled somatostatin analogs (SSAs) could represent a valid alternative to the current gold standard gallium-68-labeled SSAs for somatostatin receptor (SSTR) imaging in patients with neuroendocrine tumors (NETs), given their logistical advantages. Recently, ¹⁸F-AlF-NOTA-octreotide (¹⁸F-AlF-OC) has emerged as a promising candidate, but a thorough comparison with ⁶⁸Ga-DOTA-SSA in large patient groups is needed. This prospective, multicenter trial aims to demonstrate non-inferiority of ¹⁸F-AlF-OC compared with ⁶⁸Ga-DOTA-SSA PET in NET patients (ClinicalTrials.gov: NCT04552847). Methods: Seventy-five patients with histologically confirmed NET and a routine clinical ⁶⁸Ga-DOTATATE (n = 56) or ⁶⁸Ga-DOTANOC (n = 19) PET, performed within a 3-month interval of the study scan (median: 7 days; range: -30 to +32 days), were included. Patients underwent a whole-body PET, two hours after IV injection of 4 MBq/kg ¹⁸F-AlF-OC. A randomized, blinded consensus read was performed by two experienced readers to count tumor lesions. Following unblinding, the detection ratio (DR) was determined for each scan, i.e. the fraction of lesions detected on a scan compared to the union of lesions of both scans. The differential detection ratio (DDR; difference in DR between ¹⁸F-AlF-OC and ⁶⁸Ga-DOTATATE/NOC) per patient was calculated. Tracer uptake was evaluated by comparing SUV_max and tumor-to-background ratios (TBRs) in concordant lesions. Results: In total, 4709 different tumor lesions were detected, 3454 with ⁶⁸Ga-DOTATATE/NOC and 4278 with ¹⁸F-AlF-OC. The mean DR with ¹⁸F-AlF-OC was significantly higher than with ⁶⁸Ga-DOTATATE/NOC (91.1% vs. 75.3%; P<10-5). The resulting mean DDR was 15.8% with a lower margin of the 95% confidence interval (95% CI: 9.6%-22.0%) higher than -15%, the pre-specified boundary for non-inferiority. The mean DDR for the ⁶⁸Ga-DOTATATE and ⁶⁸Ga-DOTANOC subgroups were 11.8% (95% CI: 4.3-19.3) and 27.5% (95% CI: 17.8-37.1), respectively. The mean DDR for most organs was higher than zero, except for bone lesions (mean DDR -2.8% (95% CI: -17.8-12.2)). No significant differences in mean SUV_max were observed (P = 0.067), but mean TBR was significantly higher with ¹⁸F-AlF-OC than with ⁶⁸Ga-DOTATATE/NOC (31.7±36.5 vs. 25.1±32.7; P = 0.001). Conclusion: ¹⁸F-AlF-OC is non-inferior and even superior compared with ⁶⁸Ga-DOTATATE/NOC PET in NET patients. This validates ¹⁸F-AlF-OC as an option for clinical practice SSTR PET.

Hybrid imaging of complicating osteomyelitis in the peripheral skeleton

Diagnosing complicating osteomyelitis (COM) is clinically challenging. Laboratory tests are of limited utility, and other than isolation of the offending organism, diagnostic imaging tests are of paramount importance. Nuclear Medicine techniques play an important role in noninvasive evaluation of osteomyelitis, using both single-photon emission tomography (SPECT) and positron emission tomography (PET) radiopharmaceuticals. It is well-known that those conventional imaging modalities are not performing well in the distinction between soft-tissue and deep bone infection due to the lack of anatomical information. These difficulties have been overcome, to a great extent, with the introduction of in-line SPECT-CT and PET-CT systems which have revolutionized the field of diagnostic medical imaging. Hybrid imaging is especially useful in sites of suspected COM with underlying structural bone alterations. The first clinical studies with these integrated hybrid machines in the field of COM, including metallic implants imaging, are highly promising. In summary, WBC/AGA SPECT-CT and FDG-PET-CT seem to be the most accurate hybrid imaging modality for COM of the peripheral bone. However, there are still false positives, especially in aseptic tibial nonunions and/or metallic implants, as well as in the immediate postoperative setting. Furthermore, there is a lack of well-designed large multicentre prospective studies. Hopefully, in the future, the complementary use of morphological and functional hybrid imaging modalities may overcome some of the challenges faced in the assessment of COM.

Spatiotemporal Evolution of Radiation Myositis on 18F-FDG PET/CT Following Hypofractionated Radiotherapy of Intramuscular Melanoma Metastases

ABSTRACT

Radiation myositis is an infrequent late adverse effect of radiotherapy (RT), more commonly seen after hypofractionated regimens. We present the case of a 52-year-old woman with oligorecurrent metastatic melanoma who, several months after receiving local hypofractionated RT, developed a painful swelling at the irradiated site. As an integral part of routine oncologic follow-up, 18F-FDG PET/CT allowed accurate visualization of the affected region and when matched with RT treatment plans clearly illustrated their apparent overlap. This case demonstrates the utility of 18F-FDG PET/CT in the early detection and monitoring of radiation myositis and highlights the importance of a multidisciplinary approach in melanoma care.

Shallow-depth sequencing of cell-free DNA for Hodgkin and diffuse large B-cell lymphoma (differential) diagnosis: a standardized approach with underappreciated potential

Shallow-depth sequencing of cell-free DNA, an inexpensive and standardized approach to obtain molecular information on tumors non-invasively, has been insufficiently explored for the diagnosis of lymphoma and disease follow-up. This study collected 318 samples, including longitudinal liquid and paired solid biopsies, from a prospectively- recruited cohort of 38 Hodgkin lymphoma (HL) and 85 aggressive B-cell non-HL patients, represented by 81 diffuse large B-cell lymphoma (DLBCL) cases. Following sequencing, copy number alterations and viral read fractions were derived and analyzed. At diagnosis, liquid biopsies showed detectable copy number alterations in 84.2% of HL patients (88.6% for classical HL) and 74.1% of DLBCL patients. Of the DLBCL patients, copy number profiles between liquid-solid pairs were highly concordant (r=0.815±0.043); and, compared to tissue, HL liquid biopsies had abnormalities with higher amplitudes (P=0.010). This implies that tumor DNA is more abundant in plasma. Additionally, 39.5% of HL and 13.6% of DLBCL cases had a significantly elevated number of plasma Epstein-Barr virus DNA fragments, achieving a sensitivity of 100% compared to the current standard. A longitudinal analysis determined that, when detectable, copy number patterns were similar across (re)staging moments in refractory or relapsed patients. Further, the overall profile anomaly correlated highly with the total metabolic tumor volume (P<0.001). To conclude, as a proof of principle, we demonstrate that liquid biopsy-derived copy numbers can aid diagnosis: e.g., by differentiating HL from DLBCL, random forest modeling is represented by an area under the receiver operating characteristic curve of 0.967. This application is potentially useful when tissue is difficult to obtain or when biopsies are small and inconclusive.