18F-Fluciclovine Imaging Differentiates Progression From Treatment-Related Changes in Brain Metastases

¹⁸F-Fluciclovine (Axumin) PET/MRI accurately detected disease progression and tumor prolapse in brain metastases in patients with solid tumors and ruled out disease in non-progressors, according to findings from an ongoing study of the diagnostic performance of this imaging agent, which were presented at the 2025 Society of Neuro-Oncology (SNO) Annual Meeting and published in Neuro Oncology.^1,2

The Neuro Oncology article reported that 18F-Fluciclovine PET/MRI had a 91% diagnostic accuracy rate (95% CI, 62%-98%) for differentiating between progression and treatment-induced changes.² The sensitivity rate was 100% (95% CI, 34%-100%; n = 2/2) with this modality, meaning that it correctly identified all true progression events. The specificity rate was 89% (95% CI, 57%-98%; n = 8/9); 1 false positive was shown.

Additionally, ¹⁸F-Fluciclovine PET/MRI had a negative predictive value of 100% (95% CI, 68%-100%), meaning that it did not miss any true progressions, translating to a false negative rate of 0% (95% CI, 0%-66%). The positive predictive value was 67% (95% CI, 21%-94%).

At SNO 2025, lead study author Marina R. Schinker, BS, presented updates that occurred after abstract submission, including 1 additional true positive report, 1 additional true negative report, and 1 event that was ruled a treatment-related change awaiting final 6-month follow-up.¹ Additionally, 3 false negatives were reported in 1 patient; all were found to be invasive ductal carcinoma.

“We saw a respectable accuracy [which] gives us optimism that this is going to be a good tracer for differentiating between progression of disease and treatment-related changes, especially in comparison [with] MRI,” Schinker said in the presentation. Schinker is a client-based researcher at the University of Washington School of Medicine and Public Health in Madison.

What is the rationale for investigating 18F-Fluciclovine imaging in brain metastases?

Amino acid–based PET imaging is recommended by international working groups for the imaging of brain malignancies like brain metastases.² However, post-treatment MRI changes can mimic disease recurrence, and conventional MRI often lacks reliable specificity.¹ Misclassifying treatment-induced changes as progression of disease or vice versa can lead to unnecessary surgery, delayed treatment, or ineffective disease management.

¹⁸F-Fluciclovine is FDA approved as a diagnostic agent for PET imaging in patients with suspected prostate cancer recurrence based on elevated blood prostate-specific antigen levels following prior treatment.³ However, the imaging agent also has high tumor-to-brain contrast, which makes it an attractive candidate for imaging treated brain metastases, Schinker noted. This study is the first to examine the use of ¹⁸F-Fluciclovine after multimodal therapy in patients with brain metastases.

What was the design of the study of ¹⁸F-Fluciclovine in brain metastases? What were the characteristics of the evaluable patients enrolled so far?

This trial enrolled 11 patients with a total of 14 treated brain metastases for which there was concern for progression vs treatment-induced changes that were equivocal on prior MRI.^1,2 Patients in this study had previously received multimodal therapy (radiation therapy and immunotherapy, targeted therapy, and/or chemotherapy). Most patients were male (55%). Primary tumor types included lung cancer (37%), melanoma (18%), renal cell carcinoma (18%), breast cancer (18%), and kidney adenocarcinoma (9%).

Patients were confirmed to have brain metastases on MRI and then received radiotherapy and IMMT followed by bimonthly MRIs. Patients were then stratified into tumor prolapse (SUVmax of at least 4.8) vs treatment-induced change (SUVmax of less than 4.8) groups. Then, 6 lesions underwent surgical resection, and 5 lesions were clinically followed for at least 6 months.

What additional findings have been seen so far with¹⁸F-Fluciclovine in brain metastases?

Schinker presented a case study of a patient with a breast primary tumor and a previously treated right cerebellar metastasis who was deemed to have progression of disease during this study.¹ This patient had an SUVmax of 13, underwent surgical resection, and the ruling of disease progression to recurrent carcinoma was verified pathologically.

She presented another case study of a false positive that was shown in a patient with melanoma as their primary tumor. This patient had an SUVmax that was 9.0—above the 4.8 cutoff—and was thus ruled to have progressive disease. However, metastasis resection and pathology showed treatment-related change only. The investigators hypothesized that active treatment with immunotherapy that this patient was receiving may have contributed to the heightened SUVmax that led to a false positive classification.

This ongoing trial has enrolled 16 patients so far and plans to enroll 30 total patients; however, Schinker noted that patient recruitment has been challenging due to the enrollment requirements.

“Larger cohorts will be needed to accurately characterize the operating characteristics of this tracer,” Schinker concluded.

Disclosures: Schinker had no disclosures to declare.

References

1. Schinker MR, Oo TT, Cava JA, et al. Diagnostic performance of 18F-Fluciclovine PET/MRI in differentiating brain metastasis progression from treatment-induced changes post-therapy. Presented at: 2025 SNO Annual Meeting; November 19-23, 2025; Honolulu, HI. Abstract IMG-22.
2. Schinker MR, Oo TT, Cava JA, et al. Diagnostic performance of 18F-Fluciclovine PET/MRI in differentiating brain metastasis progression from treatment-induced changes post-therapy. Neuro Oncol. 2025;27(suppl 5):v277. doi:10.1093/neuonc/noaf201.1101
3. Axumin. Prescribing information. Blue Earth Diagnostics; July 2022. Accessed November 23, 2025. https://www.axumin.com/prescribing-information.pdf?attachment