Fractionated Stereotactic Conformal Radiotherapy for Optic Nerve Sheath Meningiomas

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Original Article

Fractionated Stereotactic Conformal Radiotherapy for Optic Nerve Sheath Meningiomas
*, B. Wharram *, R. Gunapala *, M. Brada *y F. Solda * Neuro-Oncology y

Unit, The Royal Marsden NHS Foundation Trust, London and Sutton, UK Academic Unit of Radiotherapy and Oncology, The Institute of Cancer Research, London, UK

Received 17 December 2011; received in revised form 25 February 2012; accepted 29 March 2012

Abstract Aims: To assess visual outcome, tumour control and treatment-related morbidity in patients with optic nerve sheath meningiomas (ONSMs) treated with fractionated stereotactic radiotherapy (FSRT). Patients and methods: A retrospective analysis of 45 patients (13 men and 32 women, median age 46 years) with ONSMs (51 optic nerves involved) treated in a single institution between 1997 and 2010 was carried out. FSRT was delivered to a dose of 50 Gy in 30 or 33 fractions as primary treatment in 39 patients and after surgery in six patients. Results: At a median follow-up of 30 months (range 1e13 years), the tumour control in 41 evaluable patients (four were lost to follow-up) was 100% at 5 years with no subsequent local or distant recurrence. Of the 46 evaluable optic nerves treated, 41 had residual vision (38 with impaired vision) before radiotherapy and five were blind in one eye. There was no recovery of vision in any of the blind eyes. Of 41 optic nerves with residual vision, 13 had improvement, 24 remained stable and four deteriorated; two patients (4%) developed radiation retinopathy. One patient developed a central retinal artery occlusion in the untreated eye 10 years after treatment. Conclusion: FSRT is highly effective at controlling the growth of ONSMs with improvement or stabilisation of visual deficit in 89% of the optic nerves retaining some vision, albeit with a small risk of radiation-induced retinopathy. The results support the use of FSRT as an effective approach in the management of ONSM. The lack of functional benefit in patients with severe visual impairment would argue for earlier institution of treatment before complete visual loss is established. Ó 2012 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. Key words: Meningioma; optic nerve; stereotactic radiotherapy

Introduction Optic nerve sheath meningioma (ONSM) is a rare tumour accounting for 1e2% of all intracranial meningiomas and the second most common tumour affecting the optic nerve after optic gliomas. As with other intracranial meningiomas, the most commonly affected group are women in middle age, with a peak of incidence at 41 years (range 2.5e78 years) [1]. ONSMs are mostly unilateral tumours, with about 5% involving both optic nerves, particularly seen in young patients with neurofibromatosis type 2 [2]. They wrap around the optic nerve through the subdural and subarachnoid spaces, along all paths of least resistance, Author for correspondence: M. Brada, Leaders in Oncology Care, 95 Harley Street, London W1G 6AF, UK. E-mail address: [email protected] (M. Brada).

such as vessels and dural septa [1,3]. Circumferential constriction of the optic nerve may impair the vascular supply and interfere with the axonal transport [4]. The presenting features include progressive loss of visual acuity and visual fields, proptosis, optic disc oedema, restricted eye movements, pain and lower eyelid oedema [5,6]. The combination of clinical features with magnetic resonance imaging (MRI) appearance of a thickened optic nerve on fat-suppressed T1-weighted sequences is diagnostic of ONSM, obviating the need for obtaining a tissue sample [7]. Although described in a small proportion of patients, the clinical triad of visual loss, optic atrophy and optociliary shunt veins is considered pathognomonic of ONSM. Despite indolent growth, untreated ONSMs cause progressive visual deterioration leading to blindness. ONSMs are managed with a combination of surveillance and irradiation with occasional recourse to surgical

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intervention. Surveillance is considered the appropriate approach in patients with stable vision without detectable tumour growth on imaging. Surgery is rarely carried out due to the risk to vision. Debulking surgery is of value as a cosmetic procedure in patients with disfiguring proptosis and biopsy may be necessary in cases of diagnostic difficulty [4,8,9]. Fractionated radiotherapy has been widely adopted in the treatment of ONSMs, with the aim of controlling tumour growth and preserving or improving visual function [8e39]. Fractionated stereotactic radiotherapy (FSRT) as a high precision refinement of conformal radiotherapy provides a more localised delivery of radiation, minimising the volume and the dose of radiation to the uninvolved optic apparatus and the adjacent structures, with the hope of reducing the risk of treatment-related side effects. We report a single institution experience of 45 patients treated with FSRT for ONSMs, assessing medium-term tumour control, visual outcome and treatment-related morbidity.

Materials and Methods Patients Between January 1997 and December 2010, 45 patients (51 optic nerves) with ONSM were treated with FSRT at the Royal Marsden Hospital. Indications for treatment included visual loss at presentation, progressive visual deterioration on surveillance, imaging evidence of tumour growth and a combination of these. Fractionated Stereotactic Radiotherapy Technique and Dose Prescription Technical details have been reported previously [40e43]. Briefly, patients were immobilised in a GilleThomase Cosman frame. High-resolution planning computed tomography (2 or 3 mm slice thickness) was used to outline the gross tumour volume (GTV) in five patients treated before 2004. In all other patients, the computed tomography (CT) scan was fused with a planning MRI scan. The GTV was defined as the lesion on CT and fat-suppressed T1weighted gadolinium-enhanced MRI scans. The threedimensional volume growing algorithm was used to expand the GTV by 3 mm (initially 5 mm) to generate a planning target volume (PTV). Critical structures including the eyes, optic nerves and optic chiasm were also outlined. No device to reduce eye movement was used. The PTV was treated with four non-coplanar conformal fixed fields (one patient with three fields) based on the class solution reported previously [44]. Initially, beam shaping was achieved with customised lead blocks (four patients) and subsequently with a 120 multileaf collimator (41 patients). Forty-two patients received 50 Gy in 30 fractions and three patients received 50 Gy in 33 fractions using 6 MV linear accelerator. Doses were prescribed at the isocentre according to ICRU 50 criteria with the PTV covered by the 95% isodose in three dimensions (Figure 1).

Fig 1. (a) The gross tumour volume (GTV) (purple line) and the planning target volume (PTV) (blue line) outline and (b) isodose distribution of a four-field non-coplanar beam arrangement.

Clinical Assessment and Follow-up Patients were reviewed weekly during radiotherapy for the assessment of acute toxicity and then 1, 3 and 12 months after the completion of treatment with clinical assessment of neurological status. The first ophthalmological follow-up examination with visual acuity and visual field testing was carried out 3 months after treatment. A baseline MRI scan was carried out at 3 months after the end of radiotherapy. Subsequently, patients were reviewed annually (or more often as clinically indicated) with a repeat MRI scan to assess local control. Formal ophthalmological assessment at the time of diagnosis was not available for all patients, although most presented with impairment in visual acuity. Visual outcome after treatment was defined as improved, deteriorated or stable on the basis of the ophthalmologist’s report and of the patient’s subjective assessment. Pituitary function was assessed at annual intervals in an endocrine clinic. Toxicities were documented according to

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the Common Toxicity Criteria (CTC) Version 2.0. Progression-free survival and survival were calculated from the date of FSRT using a KaplaneMeier method.

Results

survival (local control) was 100% at 5 years (18, 10 and three patients were followed for 3, 5 and 10 years, respectively). No patient had extension of disease to other sites or dissemination. Forty of 41 evaluable patients were alive at the time of analysis: one patient died of lung cancer 58 months after treatment (with stable ONSM).

Of 45 patients treated, 32 (71%) were women and 13 (29%) men, with a mean age at diagnosis of 46 years (range 26e72). In 39 (87%) patients, the diagnosis was based on the clinical findings and the characteristic appearance on MRI (Figure 2); six (13%) patients had surgery for the intracranial component of the meningioma and were referred for radiation therapy due to tumour progression and/or visual deterioration (median time to recurrence 22 months, range 10 months to 6 years). The benign nature (World Health Organization grade I meningioma) was confirmed by histology findings in all six cases. Fifty-one optic nerves were treated: 39 (87%) patients had unilateral disease and six (13%) presented with bilateral disease (one patient with neurofibromatosis type 1). Forty (78%) optic nerves presented with visual impairment, including visual acuity and/or field deficit; six (12%) eyes/optic nerves were already blind at diagnosis (three in patients with bilateral optic nerve involvement and blindness in one eye) and five (10%) had normal vision. Ten patients had proptosis, four pain, three diplopia, one restricted eye movement and one peri-orbital oedema. Patient and disease characteristics are summarised in Table 1.

Functional Improvement

Survival and Progression-free Survival

Toxicity

Four patients (9%) were lost to follow-up. No patient had progression of treated ONSM. At a median follow-up of 30 months (range 1 monthe13 years) the progression-free

Treatment was well tolerated with minimal acute sideeffects, reported as tiredness and small patches of transient hair loss.

Forty-one (89%) of 46 optic nerves evaluable (41 patients) had residual vision before radiotherapy, of whom 38 (83%) had impaired vision. No patient with blindness had recovery of vision (five optic nerves). Fourteen optic nerves (30% of all evaluable optic nerves) had improvement in vision on the affected side at a median of 5 months after treatment. At the last follow-up, 13 optic nerves (31% of those with vision) had subjective and/or objective improvements in vision: one patient, who experienced an initial improvement in vision, became blind 10 years after treatment. Improvement was therefore seen in 31% of patients with residual function. Twenty-four of the 41 patients with some residual vision (58%) had stable vision. In four optic nerves (11% of those with vision), vision deteriorated (Table 2). In the evaluable patients, two of eight showed improvement in proptosis; one of two with diplopia had recovery of double vision and one of three had improvement of pain.

Fig 2. (a) Right optic nerve sheath meningioma, post-contrast fat-suppressed T1-weighted axial magnetic resonance image (MRI) showing a globular configuration and areas of calcifications. (b) Post-contrast fat-suppressed T1-weighted coronal MRI showing the meningioma extension along the right optic nerve.


et al. / Clinical Oncology 24 (2012) e106ee112 F. Solda Table 1 Patient and disease characteristics Characteristic

No. of patients (%)

Male Female Unilateral optic nerve sheath meningioma Bilateral optic nerve sheath meningioma

13 (29) 32 (71) 39 (87)

Ocular problems

No. of optic nerves (%)

Visual impairment Proptosis Diplopia Pain Impaired ocular motility Peri-orbital oedema

46 10 3 4 1 1

6 (13)

(90) (20) (6) (8) (2) (2)

Two patients developed radiation retinopathy, one asymptomatic and one with maculopathy and subsequent visual deterioration 2 years after treatment. Following intravitreal bevacizumab [45,46] retinopathy regressed with stabilisation in vision. One patient had progressive visual deterioration immediately after treatment. Two patients with stable visual function initially, developed an extension of visual field defect and deterioration in visual acuity 26 and 74 months after treatment, respectively, both without evidence of radiation retinopathy. One patient with a left ONSM involving the chiasm with a blind left eye developed right retinal artery occlusion of embolic origin leading to complete blindness 10 years after treatment. None of the patients treated so far developed pituitary gland dysfunction.

Discussion ONSM is a rare benign tumour often leading to visual impairment and ultimately blindness. A decline in visual acuity was reported in all untreated patients at a mean of 2.2 years [47]. Although surgery might be used to remove some or all of the tumour mass, this carries a risk of blindness and after attempted curative resection, the risk of local recurrence is 15 and 75% following ‘total’ and ‘subtotal removal’, respectively [13,27,28,32]. Conventional fractionated radiotherapy inhibits tumour growth in most patients and improves vision in some [36].

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In a retrospective multicentre study of 64 patients with ONSMs treated with surgery, surgery plus radiotherapy or radiotherapy alone, the best long-term visual outcome and tumour control were reported after fractionated irradiation alone, although the 33% risk of complications was relatively high and was ascribed to non-conformal delivery of radiation [9]. FSRT is a more accurately targeted technique of irradiation with more precise tumour localisation and delivery, with a reduction in the volume of normal tissue irradiated to high radiation doses. Favourable visual outcome (improved or stable) has been reported in 83e100% of patients in previous sequential studies using FSRT [10e13,17e23,26e29,31,32,34,35,37,39] (Table 3). Similarly, 89% of the optic nerves in this study with some degree of visual impairment had stabilisation or improvement in vision, although in the absence of prospective standardised recording of the visual status, there is probably a degree of uncertainty around this. Four patients had improvement in diplopia, proptosis and pain. Improvement in vision was noted early after treatment (at a median time of 5 months), in keeping with other reports [12,20,24], presumably due to decompression of the optic nerve usually seen without detectable tumour shrinkage. The local control rate of the meningioma assessed with regular MRI imaging was 100% at 5 years, which is in keeping with other reports (Table 3). The apparent inhibition of tumour growth has been reported to be associated with a decrease in 111In octreotide uptake [10]. The irradiation of tumours within or adjacent to the orbit involving the optic nerves and close to the globe of the eye and the pituitary gland may carry a risk of developing radiation damage to those structures, leading to radiation optic neuropathy, retinopathy and hypopituitarism. The risk to brain parenchyma due to the localised nature of the stereotactic irradiation is probably small. With a total dose of 50 Gy at <2 Gy per fraction, the risk of optic nerve injury is considered to be 2% [48] and usually develops some years after treatment. In this cohort, radiation optic neuropathy cannot be distinguished from the continuing damage to the optic nerve from the ONSM itself. Nevertheless, as visual deterioration was seen soon after the completion of treatment, it is more likely to represent the effect of the tumour itself than radiation toxicity. Retinal injury has been reported after eye doses >50 Gy [49,50]. In patients with extension of the ONSM right up to the eye globe, the posterior part of the retina will have received the full radiation dose and the retinopathy

Table 2 Vision in 51 optic nerves/eyes before fractionated stereotactic radiotherapy (FSRT) and at the time of last follow-up Vision after FSRT

Vision before FSRT Normal Impaired Blind Total

Normal

3 e e 3

Impaired Improved

Stable

Deteriorated

e 13 e 13

e 21 e 21

e 4 e 4

Blind

Total evaluable

Not evaluable

Total

e

3 38 5 46

2 2 1 5

5 40 6 51

5 5

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Table 3 Summary of the reported studies of fractionated stereotactic radiotherapy (FSRT) in optic nerve sheath meningiomas No. of patients (eyes treated)

Radiotherapy characteristics

Dose (Gy)

Mean follow-up (months)

Visual outcome Improved

Stable

[28] [13] [20] [10]*

15 (16 optic nerves) 39 (42 optic nerves) 5 (6 optic nerves) 30 (33 optic nerves)

FSRT FSRT FSRT FSRT

54 54 45e54 50e54

37 35.5 (median) 24 22 (median)

6 13 4 10

40% 31% 80% 42%

9 28 1 12

[32]

6

3DCRT, FSRT

45e55

6

5

83%

[37]

1

FSRT

54

64

0

[12]*

23

FSRT

45e54

20 (median)

[17] [29] [34]*

7 4 12

FSRT FSRT FSRT

50e54 43.42e45 51.6e59.1

23 24 34 (median)

[19] [21] [35]

8 1 15 (16 optic nerves) 32 22

45 50 50e56 (20 SRS) 50e58 45e59.4

27 48 86 (median)

[23] [11]

FSRT FSRT 3DCRT, FSRT, SRS, IMRT FSRT FSRT, PRT

[31]

34

3DCRT, FSRT

[18]

11

[22]*

Decreased

Local control

Visual toxicity

No No No 12% (2 visual loss, 1 optic neuritis) 17% (ischemic optic neuropathy) 100% (radiation retinopathy) 4% (1 retinopathy and vitreous haemorrhage) No No 14% (1 vitreous haemorrhage) No No 7% (1 blindness after treatment) No 13% (3 asymptomatic radiation retinopathy) 32% (5 dry eye, 3 retinopathy, 3 cataract) No

60% 67% 20% 50%

0 1 0 2

0% 2% 0% 8%

100% 100% 100% 100%

0

0%

1

17%

100%

0%

0

0%

1

100%

100%

16

73%

5

23%

1

4%

100%

6 4 4

86% 100% 57%

0 0 2

0% 0% 29%

1 0 1

14% 0% 14%

100% 100% 100%

8 100% 0 0% 1 100% 0 0% 93% stable or improved

0 0 1

0% 0% 7%

100% 100% 100%

54 (median) 30 (median)

11 14

38% 64%

20 7

59% 32%

1 1

3% 4%

45e54

58 (median)

14

41%

17

50%

3

9%

100% 100% at 10 years _

3DCRT, FSRT, IMRT

45e54

89.6

1

9%

100%

9

3DCRT, FSRT

36e50.4

98

Visual function stable or improved in 10 (91%) 7 100% 0 0%

0

0%

100%

[26] [27]

5 109y (113 optic nerves)

FSRT FSRT

50.4 50.4e54

26 (median) 50.5 (median)

2 12

40% 13%

3 68

60% 75%

0 11

0% 12%

[39]* Present study*

40 (41 optic nerves) 45 (51 optic nerves)

FSRT FSRT

22e66 50

60 (median) 30 (median)

14 13

44% 31%

15 24

47% 58%

3 4

9% 11%

100% 100% at 3 years, 98% at 5 Years 100% 100%

3DCRT, three-dimensional conformal radiotherapy; SRS, stereotactic radiosurgery; IMRT, intensity-modulated radiotherapy. * Visual outcome for patients retaining useful vision. y Information on visual outcome available for 91 patients.

11% (1 radiation retinopathy) No No

No 7% (2 radiation retinopathy, 1 blindness)


et al. / Clinical Oncology 24 (2012) e106ee112 F. Solda

Reference


et al. / Clinical Oncology 24 (2012) e106ee112 F. Solda

noted in two patients is probably, at least in part, radiation induced. However, contribution from the longstanding mechanical compression cannot be excluded. Retinopathy has been reported 2e4 years after FSRT [12,32,37,51]. Other late effects have been ascribed to radiotherapy of benign tumours, such as increased incidence of cerebrovascular accidents and an excess of cerebrovascular mortality [52,53] and an increased risk of presumed radiation-induced second tumours [54] all in patients with pituitary adenoma. However, these have not been reported in patients receiving radiation for cranial meningiomas. Although none of these presumed radiation-induced late effects were seen, the size of the cohort and the limited follow-up do not preclude the emergence of such complications some decades later.

[10]

[11]

[12]

Conclusions

[13]

The reported study supports the evidence of the efficacy of FSRT in the treatment of ONSMs in terms of long-term tumour control and improvement or stabilisation of vision. The lack of recovery of vision in the severely impaired optic nerve would argue in favour of treatment before significant loss of vision.

[14]

Acknowledgements This study was supported by the Neuro-oncology Research Fund. UK hospitals receive a proportion of their funding from the NHS Executive; the views expressed are those of the authors and not necessarily those of the NHS Executive. The authors would like to thank our ophthalmological colleagues Mr P. Riordan Eva, Mr J.S. Elston, Mr R. Whitelocke, Mr M.A. Burdon and Lt Col A.S. Jacks for referring patients for treatment and for their contribution to the study.

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