[Malignant brain tumors after radiation - glioblastomas after operation and radiation of meningiomas - 2 case reports]

The incidence of second brain tumors related to cranial irradiation

Secondary brain tumor (SBT) is a devastating complication of cranial irradiation (CI). We reviewed the literature to determine the incidence of SBT as related to specific radiation therapy (RT) treatment modalities. The relative risk of radiation-associated SBT after conventional and conformal RT is well established and ranges from 5.65 to 10.9; latent time to develop second tumor ranges from 5.8 to 22.4 years, depending on radiation dose and primary disease. Theories and dosimetric models suggest that intensity-modulated radiation therapy may result in an increased risk of SBT, but clinical evidence is limited. The incidence of stereotactic radiosurgery-related SBT is low. Initial data suggest that no increased risk from proton therapy and dosimetric models predict a lower incidence of SBT compared with photons. In conclusion, the incidence of SBT related to CI is low. Longer follow-up is needed to clarify the impact of intensity-modulated radiation therapy, proton therapy and other developing technologies.

Spot-scanning proton radiation therapy for recurrent, residual or untreated intracranial meningiomas

BACKGROUND AND PURPOSE

To assess the safety and efficacy of spot scanning proton beam radiation therapy (PRT) in the treatment of intracranial meningiomas.

PATIENTS AND METHODS

Sixteen patients with intracranial meningioma (histopathologically proven in 13/16 cases) were treated with PRT between July 1997 and July 2002. Eight patients had skull base lesions. Thirteen patients received PRT after surgery either as adjuvant therapy for incomplete resection (eight patients) or for recurrence (five patients). Three patients received radical PRT after presumptive diagnosis based on imaging. The median prescribed dose was 56 CGE (range, 52.2-64, CGE=proton Gy X 1.1) at 1.8-2.0 CGE (median, 2.0) per fraction. Gross tumor volume and planning target volume ranged from 0.8 to 87.6 cc (median, 17.5) and 4.6-208.1 cc (median 107.7), respectively. Late ophthalmologic and non-ophthalmologic toxicity was assessed using the Subjective, Objective, Management and Analytic scale (SOMA) of the Late Effects of Normal Tissue scoring system and National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE, v3.0) grading system, respectively. The median follow-up time was 34.1 months (range, 6.5-67.8).

RESULTS

Cumulative 3-year local control, progression-free survival and overall survival were 91.7, 91.7 and 92.7%, respectively. No patient died from recurrent meningioma. One patient progressed locally after PRT. Radiographic follow-up (median, 34 months) revealed an objective response in three patients and stable disease in 12 patients. Cumulative 3-year toxicity free survival was 76.2%. One patient presented with radiation induced optic neuropathy (SOMA Grade 3) and retinopathy (SOMA Grade 2) 8.8 and 30.4 months after treatment, respectively. These patients with ophthalmologic toxicity received doses higher than those allowed for the optic/ocular structures. Another patient developed a symptomatic brain necrosis (CTCAE Grade 4) 7.2 months after treatment. No radiation-induced hypothalamic/pituitary dysfunction was observed.

CONCLUSIONS

Spot-scanning PRT is an effective treatment for patient with untreated, recurrent or incompletely resected intracranial meningiomas. It offers highly conformal irradiation for complex-shaped intracranial meningiomas, while delivering minimal non-target dose. Observed ophthalmologic toxicity is dose-related.