Impact of Gamma Knife Radiosurgery on the neurosurgical management of skull-base lesions: The Combined Approach

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1 Radiosurgery as part of the neurosurgical armamentarium: Educational Symposium November 24 th 2011 Impact of Gamma Knife Radiosurgery on the neurosurgical management of skull-base lesions: The Combined Approach Prof. Roy Thomas Daniel Médecin-Chef, Service de Neurochirurgie CHUV, Lausanne, Switzerland First Anniversary Gamma Knife Center CHUV

2 Skull Base surgery Anterior Cranial Fossa Meningioma Olfactory groove Planum sphenoidale Carcinoma Esthesioneuroblastoma Middle Cranial Fossa Meningioma Diagphragmma sellae Clinoid /Optic foramen Cavernous sinus Schwanomma (5th N) Pituitary adenoma Posterior Cranial Fossa Vestibular schwanomma Posterior Petrous meningioma

3 When to treat?! And which modality? Large / symptomatic lesions -> microsurgery - Total / subtotal removal? - Remnant: to treat or not to treat? When? Small to medium-size symptomatic lesions : -> microsurgery or radiosurgery? Small to medium-size asymptomatic lesions : -> microsurgery or radiosurgery? When? - clinical and radiological follow-up? - treatment upfront? good knowledge of the treatment outcomes (location, age, ) and natural history (highly variable)

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5 Grade I: 0-4 points Grade II: 5-7 points Grade III: 8-12 points

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7 SRS: TREATMENT PLANNING = DOSIMETRY 1. To define the optimal dose distribution to the target-volume = conformity : quality of the fit between the dose volume and the target 2. To define the optimal dose distribution to the normal tissue = selectivity : to minimize irradiation of healthy tissue and critical areas Limiting factor = volume of the target volume dose outside of the target complications ( fonction of the location and of the treated indication )

8 SRS: TREATMENT PLANNING TARGET VOLUME

9 DOSIMETRY TARGET VOLUME Microsurgery (combined approach) Undertreatment

10 Vestibular Schwanomma

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13 Vestibular Schwanomma: Combined Approach 2-4 ma SR S ma

14 6 m Post GK Post op (early) Post op 6 m

15 6 m post op

16 Rendina christina 6 m post op

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18 Petroclival meningioma IAM Petrous bone

19 Specific issues with petro-clival meningiomas More variable clinical presentation More variability in surgical approaches Retrolabrynthic pre sigmoid Trans labrynthic or trans cochlear Middle fossa trans petrous Retrosigmoid More compression-related symptoms, needing surgery (more limited response to radiosurgery) If radical resection is too risky -> combined approach Brain stem = 12 Gy (like the prescription dose) less limitation than with cavernous sinus lesions (not always. ; cf. post-radiation therapy) New functional challenges: e.g. cochlea (4 Gy)

20 76% radiological tumor growth 63% functional deterioration with tumor growth

21 In our opinion, clival meningiomas are inoperable. (Castellano and Ruggiero, 1953) Clivus meningiomas in particular have until recent years been uniformly lethal. The outlook of such patients must be bettered by achieving earlier diagnosis, by improving surgical technique and better understanding on the pathological anatomy. (Yasargil, 1980) In nearly all cases, the patient came out in worse clinical and neurological conditions after surgery than before and therefore need constant, meticulous assistance. (Bricolo, 1992) By a combined application of advanced microsurgical techniques, thoughtful, intraoperative decision making with limited surgical aggressivity, and in selected patients, with small remnants simple observation or alternative or adjunct radiosurgery, excellent results as measured by tumor control and preservation of quality of life can be achieved. (Seifert, 2010)

22 Radiosurgery for meningiomas Long-term clinical & scientific track record Highly reproducible results Therapeutic window is well-known: 12 Gy (min) 14 Gy 15/16 Gy (?) Tumor control rate > 90% (usually > 95-97%), for WHO grade I meningiomas (up to 10 Y) Decrease in size (± 50%) or remain stable Selection bias towards lesion unfavorable for surgery: skull base > sinus involvment > other locations Primary RS post-op (adjuvant or recurrence) RS Complications < 10%, mostly transient - cranial nerves (skull base) - edema-related (convexity)

23 Petroclival meningioma 7th N 5th N 7th N

24 Middle Cranial Fossa Tumours Clinoidal meningioma Trigeminal schwanomma Pituitary adenoma

25 Specific issues with Middle fossa meningioma radiosurgery Total excision of tumours in or around the cavernous sinus 50% cranial nerve morbidity Small intracavernous lesions: Radiosurgery Larger tumours need combined approach The optic nerve is mostly sensitive to radiation For radiosurgery: 8 Gy (up to 10 Gy?) no contact between the tumor and optic tract - combined approach (with opening of optic canal when needed) - undertreatment (lower dose at interface) The content of the cavernous sinus is considered resistant to high-dose radiosurgery (risk of carotid obliteration?)

26 ON(Ex) ON(Ex) Chiasmopexy & Hypophysopexy ON ON(In) SOF ICA ON(In)

27 Optic foramen Meningioma ED ON ID ON

28 Pituitary Adenoma Anterior Lobe: FSH LH ACTH TSH Prolactin GH Posterior Lobe: ADH Oxytocin

29 Microadenomas (< 10 mm)

30 Hardy s classification Macroadenomas (>10 mm) A B C D

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32 The Trans-sphenoidal approach Transsphenoidal Line of Vision on MRI for Pituitary Tumor Surgery Neurol India, 2002; 50 :

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34 Non-functional Pituitary Adenoma Stage 1 Stage 2 Stage 3

35 6m post op: IGF1 still high SRS

36 Combined Treatment (Microsurgery +Radiosurgery) for skull base tumours Avoids the need (in most cases) for complicated and invasive skull base approaches Potential for cranial neuropathy greatly decreased Low risk of permanent complications Long-term tumor control needs to be studied in this subgroup Growth pattern is unpredictable careful imaging follow-up is mandatory Will become standard of care as long term results emerge from this approach