Surveillance Protocol for Recurrent Meningioma

Surveillance Protocol Based on WHO Grade

• The American College of Radiology recommends MRI brain without and with IV contrast every 6-12 months for WHO grade 1 tumors 1, 2, 3
• For WHO grade 1 meningiomas, consider extending intervals after tumor has demonstrated stability, and annual surveillance should continue for at least 10 years due to potential for late recurrences 4, 5
• The American College of Radiology suggests more frequent MRI surveillance is required for WHO grade 2 tumors compared to WHO grade 1 tumors 1, 2
• For WHO grade 2 (atypical) meningiomas, MRI brain without and with IV contrast every 3-6 months initially, and consider perfusion MRI as a helpful adjunct to conventional MRI 1, 2, 3
• For WHO grade 3 (malignant) meningiomas, MRI brain without and with IV contrast every 3 months initially, and consider adding spine imaging if there are concerns for CSF dissemination 1, 2, 6

Advanced Imaging Considerations

• The American College of Radiology recommends considering additional imaging for suspected recurrence with equivocal findings on conventional MRI, differentiating between tumor recurrence and post-treatment changes, and when tumor extension is unclear on conventional imaging 1, 2, 3, 7
• MRI perfusion is useful for meningioma grading and can help detect recurrence, according to the American College of Radiology 1, 2
• Somatostatin receptor (SSTR) PET imaging provides superior detection sensitivity compared to contrast-enhanced MRI alone, as suggested by the American College of Radiology 3, 7

Special Considerations for High-Risk Patients

• Patients with genetic syndromes associated with meningiomas (NF2, SMARCE1, etc.) require specialized surveillance, according to the Clinical Cancer Research journal 6, 8
• For SMARCE1-associated clear cell meningiomas, yearly MRI brain and spine until age 30, then every 2-3 years, as recommended by the Clinical Cancer Research journal 6
• For LZTR1-associated meningiomas, MRI brain and spine every 2-3 years, beginning at age 15-19, as suggested by the Clinical Cancer Research journal 6

Practical Implementation

• Continue surveillance for at least 10 years for all meningioma grades, as recommended by the British journal of neurosurgery 5
• Late recurrences are not uncommon, particularly with higher-grade tumors, according to the British journal of neurosurgery 5
• MRI should include pre- and post-contrast T1-weighted sequences, as suggested by the British journal of neurosurgery 5
• Include T2 FLAIR sequences to evaluate for vasogenic edema, according to the American College of Radiology 1, 2
• SWI sequences are valuable for detecting intratumoral calcifications, as recommended by the American College of Radiology 1, 2

Common Pitfalls and Caveats

• Post-treatment changes can mimic tumor recurrence on conventional MRI, as noted by the Praxis Medical Insights 3, 7
• Inflammatory lesions may present with increased uptake on SSTR PET, leading to false positives, according to the Praxis Medical Insights 7
• Rare cases of meningioma may show decreased or absent uptake on SSTR PET, as suggested by the Praxis Medical Insights 7
• The postradiotherapy MRI should be considered the "new baseline" rather than the postsurgical MRI, according to the American College of Radiology 1, 2

Non-Contrast MRI for Surveillance of Recurrent Meningiomas

Rationale for Non-Contrast MRI in Meningioma Surveillance

• Non-contrast MRI sequences (T1, T2, FLAIR, DWI, SWI) provide valuable information about tumor cellularity, intratumoral blood products, mineralization, and the presence of CSF clefts and subjacent parenchymal edema, as recommended by the American College of Radiology 9, 10
• These sequences are particularly helpful in the post-treatment surveillance context for meningiomas, allowing assessment of tumor characteristics without the risks associated with gadolinium-based contrast agents, according to the American College of Radiology 10

Diagnostic Value of Non-Contrast MRI

• T2/FLAIR imaging can assist in determining extraaxial location by demonstrating a CSF cleft and can further demonstrate the presence of any subjacent parenchymal edema, as noted by the American College of Radiology 9

Surveillance Protocol Based on WHO Grade

• More frequent surveillance is required for WHO grade 2 (atypical) and grade 3 (malignant) meningiomas, with the American College of Radiology recommending MRI surveillance intervals based on WHO grade 11

When Contrast Enhancement May Still Be Needed

• Contrast-enhanced MRI may be necessary in specific scenarios, such as when evaluating for leptomeningeal metastases, as recommended by the American College of Radiology 9

MRI Surveillance Intervals for Meningioma

WHO Grade‑Specific Imaging Frequency

• For WHO grade 1 (benign) meningiomas, the American College of Radiology recommends MRI of the brain with and without IV contrast every 6–12 months; intervals may be extended after documented stability, and surveillance should continue for a minimum of 10 years because late recurrences can occur 12.
• For WHO grade 2 (atypical) meningiomas, the American College of Radiology advises a more intensive schedule than grade 1, typically MRI with and without IV contrast every 3–6 months in the early postoperative period 12.
• For WHO grade 3 (malignant) meningiomas, the American College of Radiology recommends MRI with and without IV contrast every 3 months initially 12.

Tailoring Surveillance to Tumor Biology

• Imaging frequency can be individualized using combined histologic and molecular profiling to optimize follow‑up intervals 12.

Post‑Treatment Imaging Baselines

• After radiotherapy, the post‑radiotherapy MRI should be treated as the new baseline for subsequent surveillance rather than the immediate postoperative scan 12.

Advanced Imaging Modalities

• Somatostatin receptor PET/CT or PET/MRI provides more accurate assessment of residual or recurrent disease in WHO grade 2 and 3 meningiomas and is recommended as an adjunct to conventional MRI 12.
• When conventional MRI yields equivocal findings for suspected recurrence, when distinguishing tumor recurrence from post‑treatment changes, or when tumor extension is unclear, additional imaging modalities (e.g., perfusion MRI, SSTR PET) should be considered 12.
• Somatostatin receptor PET demonstrates superior detection sensitivity compared with contrast‑enhanced MRI alone, particularly for higher‑grade (WHO 2‑3) meningiomas 12.

Recommended MRI Technical Protocol

• Essential sequences include pre‑ and post‑contrast T1‑weighted images, T2‑FLAIR for edema assessment, and SWI for intratumoral calcifications; perfusion MRI may be added for grading and recurrence detection 12.

Surveillance After Stereotactic Radiosurgery (SRS)

• Following SRS, close imaging surveillance is advised during the first several years because most tumors stabilize over time 13.
• Approximately 95 % of treated meningiomas reach a steady state by 5 years and 90 % by 10 years post‑SRS 13.
• Once steady state is confirmed, routine radiological follow‑up intervals may be safely lengthened 13.
• Clinical follow‑up should continue with regular neurological examinations and ophthalmologic assessments 13.