CNS Tumors Meningioma

MENIGIOMAS

Etiology and Epidemiology

  • Most common primary brain tumor and 25% of all CNS tumors
  • Female > Male by a factor of 2
  • Median age is 65 years old
  • Benign (mostly) lesions from the arachnoids layer of the meninges.

Risk Factors

  • Prior exposure to ionizing radiation (10-fold increase) with 20-40 year latency
  • Neurofibromatosis type 2 (NF2)

Pathology

  • Malignant varieties are recognized by
  • Psammoma bodies may be present
  • Clinical behavior such as rapid growth, recurrence, or invasiveness
  • Microscopic features such as cellular or nuclear anaplasia, mitotic figures
  • Atypical Meningioma Characterized by
    • Brain invasion
    • Mitotic index > 4 per 10 HPF
    • Sheeting
    • Small cell formation
    • Hypercellularity
    • Necrosis
  • Anaplastic Characterized by
    • Mitotic index > 20 per 10 HPF
    • Sarcoma-, carcinoma-, or melanoma-like histology
  • Transitional subtype carries a worse prognosis than memingotheliomatous (syncytial)
  • Angioblastic is worse than Transitional

WHO Grade II

  • Clear cell
  • chondroid histologic variants
  • atypical

WHO Grade II

  • Rhabdoid
  • paillary variants
  • anaplastic

Treatment

Surgery is the mainstay of treatment.
Radiation indication of

  • RT is indicated for
    • subtotal resection
    • recurrent disease
    • not a surgical candidate
    • unresectable tumor,
    • histologically malignant, atypical, or haemangiopericytic variant.

Radiation (Standard fractionation) doses

  • 5400 cGy/30 fractions for benign
  • 6000 cGy/30 fractions for atypical or malignant.

Radiation (SRS) Dose

  • 16 Gy for bengn
  • > 20 Gy for atypical and malignant (WHO III)(Ref. Kano H)

Results

  • Overall survival at 5 years is ~ 60%, with decreasing overall survival associated with older age.

Malignant meningioma[1]

Recurrence Rate
GTR 33%
GRT + RT 12%
STR 100%
STR + RT 55%
  • GTR: complete resection
  • STR: partial resection

Benign meningioma[2]

15-recurrence rate 15-CSS
GTR 24% 88%
STR 70% 51%
STR + RT 13% 86%
  • GTR: complete resection
  • STR: partial resection
  • CSS: Cause specific survival
  • 90% control rate at 15 years for benign meningioma after complete resection
  • with similar results with stereotactic radiosurgery and standard radiation

Hemangiopericytoma

General

Radiograph

  • similar to meningioma
  • intensly enhancing like meningioma
  • but lacks calcification

Clinical Course

  • locally aggressive with propensity for local recurrence after GTR
  • 80% late local, leptomeningeal and metastatic failure rate at 10- to 15-years.

Workup

  • CT chest/abdomen
  • bone scan
  • spinal MR

Therapy

  • Resection
  • Adjuvant RT
Bibliography
1. Karlsson UL, Leibel SA, Wallner K. Brain tumors:In: Perez CA, Brady LW, eds. Principles and practice of radiation oncology, 2nd ed. Philadelphia: JB Lippincott, 1992:515.
2. Wilson C. meningiomas: genetics, maligancy, and the role of radiation in induction and treatment. J Neurosurg 194, 81: 666.
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