Hypofractionated high-energy proton-beam irradiation is an alternative treatment for WHO grade I meningiomas

Abstract

BackgroundRadiation treatment is commonly employed in the treatment of meningiomas. The aim of this study was to evaluate the effectiveness and safety of hypofractionated high-energy proton therapy as adjuvant or primary treatment for WHO grade I meningiomas.MethodA total of 170 patients who received irradiation with protons for grade I meningiomas between 1994 and 2007 were included in the study. The majority of the tumours were located at the skull base (n = 155). Eighty-four patients were treated post subtotal resection, 42 at tumour relapse and 44 with upfront radiotherapy after diagnosis based on the typical radiological image. Irradiation was given in a hypofractionated fashion (3–8 fractions, usually 5 or 6 Gy) with a mean dose of 21.9 Gy (range, 14–46 Gy). All patients were planned for follow-up with clinical controls and magnetic resonance imaging scans at 6 months and 1, 2, 3, 5, 7 and 10 years after treatment. The median follow-up time was 84 months. Age, gender, tumour location, Simpson resection grade and target volume were assessed as possible prognostic factors for post-irradiation tumour progression and radiation related complications.ResultsThe actuarial 5- and 10-year progression-free survival rates were 93% and 85% respectively. Overall mortality rate was 13.5%, while disease-specific mortality was 1.7% (3/170 patients). Older patients and patients with tumours located in the middle cranial fossa had a lower risk for tumour progression. Radiation-related complications were seen in 16 patients (9.4%), with pituitary insufficiency being the most common. Tumour location in the anterior cranial fossa was the only factor that significantly increased the risk of complications.ConclusionsHypofractionated proton-beam radiation therapy may be used particularly in the treatment of larger World Health Organisation grade I meningiomas not amenable to total surgical resection. Treatment is associated with high rates of long-term tumour growth control and acceptable risk for complications.

Proton-beam therapy or photon-beam radiosurgery for WHO grade I meningiomas?

“…This spherical geometric arrangement of entry points around the head results in a far better target conformality and, accordingly, in a superior protection of OAR. The full or partial inclusion of parts of the optic apparatus in the radiation field in 66% of patients, as reported in this issue's publication on PBT [3], would be unacceptable in RS. Target conformality of PBT may be sufficient for other organs, such as prostate or pancreas, but it is not for the brain.…”

“…It is of great value to see this study's [3] results of PBT in patients with WHO grade I meningiomas. Unfortunately, they do not compare convincingly to results of RS for the same tumour class.…”

“…PBT's share of radiotherapy was 0.6% in the US in 2012 [4]. In this issue of Acta Neurochirurgica, Vlachogiannis et al [3] present their experience with PBT in 170 patients with WHO grade I meningiomas. As opposed to the classical use of PBT, their patients have neither a rare tumour type nor do they belong to the paediatric age group.…”

“…The authors' paper raises a number of issues. Is it really reasonable to use PBT for tumour volumes up to 64 cm 3 or an average tumour volume of 13 cm 3 ? If PBT should be considered for larger tumours, why not adopt radiosurgical techniques such as volume-or dose-staging?…”

“…Many questions remain unanswered and PBT may still profit a lot from adopting neurosurgical approaches to classical neurosurgical neoplasms. Therefore, the title's claim that Bhypofractionated high-energy proton beam irradiation is an alternative treatment for WHO grade I meningiomas^ [3] needs to be questioned. Is that really so?…”