Objective:

To present a case of delayed radiation necrosis (RN) occurring several years after stereotactic radiosurgery (SRS) and explore the potential role of systemic immune activation in its development.

Approach:

• Case Presentation: A 66-year-old female with metastatic non-small cell lung cancer underwent SRS for brain metastases and later developed new enhancing lesions 46 months post-treatment, which were diagnosed as RN.
• Imaging and Diagnosis: Serial MRIs and fluciclovine PET scans were used to monitor the patient, revealing fluctuating enhancement and edema, complicating the differentiation between RN and recurrent metastases.

Key Findings:

• Delayed RN can occur several years after SRS, presenting diagnostic challenges.
• Advanced imaging modalities may not effectively distinguish RN from recurrent tumors.
• The relationship between COVID-19 vaccinations and delayed RN requires further investigation.

Interpretation:

This case suggests that chronic immune priming and systemic inflammatory activation may be factors in the delayed manifestation of RN in irradiated CNS tissue.

Limitations:

• Causality between COVID-19 vaccination and RN cannot be established based on this case.
• The role of immunotherapy in exacerbating RN is not clearly defined in this instance.

Conclusion:

This case highlights the complexities involved in diagnosing delayed RN in patients with prior immunotherapy and vaccination.