Session Item

Radiation-induced meningiomas (RIM) are the most common intracranial secondary neoplasm in childhood cancer survivors. Although routine MRI screening for RIM remains controversial, many patients present asymptomatically.  The natural history and long-term outcomes for asymptomatic RIM are poorly understood.  This retrospective study describes the radiological growth rate and clinical outcomes of asymptomatic RIM in cancer survivors previously treated with cranial or spinal radiotherapy.

Eligibility included long-term cancer survivors enrolled in the Peter MacCallum Late Effects Clinic with ≥1 RIM identified on MRI from 1/1/1990 to 1/11/2015.  MRI scans were centrally reviewed.  Radiological growth rate was calculated for patients managed by active surveillance with ≥2 serial MRI scans available for central review.

Fifty-two patients were included in the study: median age at RT was 5.6 (range, 0.9-30.3) years, median RT dose was 40Gy.  At RIM diagnosis, median age was 33.9 (range, 13.8-54.1) years, with median latency period of 25.5 (range, 8.8-53.2) years.  37% of patients had multifocal RIM.  88% of patients were asymptomatic at presentation.

A total of 87 RIM were identified.  Median follow-up was 11 years.  RIM location was convexity (48%), falcine/tentorial (34%), basal (16%), and spinal (2%).  Initial RIM management was active surveillance (77%), upfront surgery (21%), SRS (1%), chemotherapy (1%). 

Active surveillance was adopted for 67 RIM in 40 patients.   Of these patients, 82.5% had RIM diagnosed on MRI screening.  At 10 years, the cumulative actuarial incidence of surgery for initially surveilled RIM was 21% (95%CI, 12%-31%).  The most common indication for surgery was asymptomatic tumour growth (62.5%).   Neurological sequelae due to RIM progression was reported in 2 (5%) patients on active surveillance.

MRI data was available for 61 (91%) RIM on active surveillance.  Mean tumour volume at diagnosis was 0.53cm³ (SD=1.14).  Median absolute growth rate was 0.05cm³/year (IQR 0.01-0.11); median relative growth rate was 26% per year (IQR 7-79).  Radiological growth pattern of individual RIM is shown in Figure 1.

Resection was performed for 33 RIM (30 patients), 54.5% at diagnosis and 45.5% after active surveillance.  Pathological grade was WHO Grade I (85.2%), II (11.1%), III (3.7%).  Gross total resection was achieved in 79%.  Following resection, actuarial 10-year local recurrence rate was 12% (95%CI: 3-29).

There were 8 deaths: 1 due to RIM.  OS was 88% (95%CI, 74%-95%) at 10 years.

Active surveillance is a safe initial strategy for small, asymptomatic RIM, with low rates of neurological morbidity.  Asymptomatic RIM typically demonstrate slow radiological growth.  However, long-term MRI surveillance for asymptomatic RIM is required, as 21% of patients will require surgical intervention within 10 years, most commonly for asymptomatic tumour growth.