Radiation-induced meningiomas: the paradox of radiation treatment

Case report: Low-dose radiation-induced meningioma with a short latency period

Patients with radiation-induced meningioma (RIM), most of whom had received head radiation therapy or had been exposed to ionizing radiation during childhood or adolescence, are at risk of developing cranial meningiomas throughout their lifetimes because of the long latency period. Although intermediate-to-high-dose ionizing radiation exposure is an established risk factor for RIM, risk factors for low-dose RIM remain incompletely defined. This study presents the case of a 56-year-old woman diagnosed with radiation-induced giant meningioma 2.5 years after undergoing an interventional embolization procedure for a brain aneurysm. This is the first report of RIM attributable to a brain intervention with an extremely short latency period. The total radiation dose received by the patient during the operation was 1367.3 mGy, representing a low dose. Our case report strengthens the evidence that even low radiation doses can increase the risk of RIM. These findings provide a realistic basis for the theoretical study of RIM and suggest some new ideas for RIM treatment. The need for caution in the use of radioactive treatments and optimization of interventional procedures is highlighted.

Radiation-induced meningiomas

Radiation-induced meningiomas (RIMs) became more common as the use of ionizing radiation was adopted in the treatment of medical conditions, both benign and malignant. Currently, RIMs represent the most common radiation-induced tumors. They are heterogeneous in terms of patient characteristics, radiographic appearance, genetics, pathology, symptoms, and management strategies. They tend to occur in a younger population and are generally more aggressive in nature than their spontaneous counterparts. Their characteristics also vary based on the dose of radiation received, which is most commonly separated into low dose (<10Gy) and high dose (>10Gy). The importance of the dosing classification is that it can provide insight into the nature and biologic behavior of the tumor. Given their heterogeneity, RIMs pose significant challenges in management. While surgical resection remains the preferred treatment when feasible, recent data supports stereotactic radiosurgery (SRS) as a comparable alternative. Although there is more knowledge about the molecular pathways leading to RIMs, targeted drug therapy is still limited and is the focus of current research.

Surgical management of medium and large petroclival meningiomas: a single institution's experience of 199 cases with long-term follow-up

BACKGROUND

Petroclival meningiomas (PCMs) were once regarded as 'inoperable' due to their complex anatomy and limited surgical exposure. This study aimed to evaluate the long-term outcomes of surgically treated PCMs larger than 2 cm.

METHODS

A series of 199 consecutive patients (137 females, 68.8 %) with PCMs larger than 2 cm from between 1993 and 2003 were included. The clinical charts, radiographs, and follow-ups were evaluated.

RESULTS

Gross total resection (GTR) was achieved in 111 (55.8 %) patients, subtotal resection (STR) in 65, and partial resection (PR) in 23. Cranial nerve dysfunctions were the most common complications and occurred in 133 (66.8 %) cases. The surgical mortality was 2.0 %. The Karnofsky Performance Scale (KPS) scores significantly decreased 1 month after the operations (preoperative KPS = 76.8 and postoperative KPS = 64.8; p = 0.011, Paired-samples t test). Long-term follow-ups were obtained in 142 patients, the follow-up duration was 171.6 months, and the most recent KPS was 83.2. Permanent morbidities remained in 24 patients (18.9 %). Multivariate analysis revealed that brainstem edema and tumors larger than 4 cm in diameter were independent risk factors in terms of outcomes (KPS < 80). The recurrence/progression rates were 14.5, 31.8, and 53.3 % for the GTR, STR, and PR cases, respectively (p = 0.002, Pearson χ (2) test). Gamma Knife radiosurgery for the remnants exhibited good tumor control.

CONCLUSIONS

Favorable outcomes and low mortality were achieved with the microsurgical management of medium and large PCMs; however, the rates of cranial nerves dysfunction remained high. Radically aggressive resection might not be judicious in terms of postoperative morbidity. The preoperative evaluations and intraoperative findings were informative regarding the outcomes. The low follow-up rate likely compromised our findings, and additional consecutive studies were required.