Neurosurgery notes/Tumours/Meningioma/Sphenoid wing (Lateral and middle)

Sphenoid wing (Lateral and middle)

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Meningioma

General

  • Surgery for sphenoid wing meningiomas poses a variety of problems reflecting the complex anatomy of the sphenoid region.
    • Tumours of the outer third of the sphenoid ridge and many small middle wing tumors are essentially convexity meningiomas with regard to clinical presentation and surgical treatment
    • More medially located sphenoid wing meningiomas may compress and encase the carotid artery and its branches, the optic apparatus, and the pituitary stalk.
  • Sphenoid wing meningiomas may show prominent dural involvement (en plaque growth).

Classification of Sphenoid Meningiomas

Most neurosurgeons broadly distinguish between

  • Globular tumors of the lateral and middle third of the sphenoid ridge
  • Medial wing tumors
    • Tumors of the medial sphenoid wing are often subclassified based on the presence of invasion of the cavernous sinus.
  • Hyperostosing/en plaque (sphenoorbital) meningiomas

Cushing and Eisenhardt

Lateral (outer) or pterional

  • Greater chance of en plaque meningioma
  • Higher association with headaches
  • Can be large globular tumors
  • Arterial supply from:
    • Superficial temporal artery,
    • Middle meningeal arteries,
    • Anterior meningeal artery

Middle

  • May become large before they are diagnosed or turn symptomatic
  • Greater association with seizures
  • Arterial supply
    • Branches of ethmoidal arteries

Medial or clinoidal

  • Cranial nerves II and III may be affected early
  • Surgically challenging with lower chance of complete resection
  • Arterial supply
    • ECA
      • Middle meningeal artery
      • Ascending branch of pharyngeal artery,
      • Recurrent branch of ophthalmic artery via superior orbital fissure
    • ICA
      • Meningohypophyseal trunk or both.

Bonnal et al and Brotchi and Pirotte

Group A

  • Clinoidal tumors
    • Invasion of the cavernous sinus is listed as one characteristic of these growths.
    • Some authors use the term clinoidal meningiomas to exclusively refer to meningiomas originating from the anterior clinoid process rather than as a more general designation for middle sphenoid wing meningiomas.
  • Al-Mefty (anterior clinoidal meningioma) classification
      • Group 1
        • Tumors originating proximally to the end of the carotid cistern, which directly enwrap the carotid artery
        • Rare, and the lack of an arachnoidal dissection plane between the tumor and the carotid artery may be related to other factors such as repeat surgery.
      • Group 2
        • Point of origin at the superolateral aspect of the clinoid process and an arachnoidal membrane interposed between the tumor and the carotid artery
      • Group 3
        • Tumours originating medially in the region of the optic foramen
        • Aka: optic foramen, optic sheath, or optic canal meningiomas.
      Anterior clinoidal meningioma classification Al•Mefty group Group I Group Il Group Ill Suprasellar extention B c > 4 cm (giant)
       

Group B

  • Meningiomas en plaque with hyperostosis of the sphenoid bone (i.e., sphenoorbital meningiomas)
  • Roser et al
    • Further sub-divided hyperostosing/en plaque (sphenoorbital) tumours into
      • Meningiomas en plaque with and without cavernous sinus infiltration,
      • Purely intraosseous meningiomas.
  • It is recognized that the designation pterional chosen by Cushing for these growths may not be fully appropriate.
    • Because they are technically a convexity meningioma

Group C

  • Large invasive tumors of the sphenoid ridge (“invasion en masse”)
    • These tumors are thought to combine features of both group A and B tumors (i.e., globular and invasive growth en plaque).

Group D

  • Globular tumors of the middle sphenoid ridge

Group E

  • Globular tumors of the lateral sphenoid ridge

Numbers

  • Sphenoid wing meningiomas account for 11 to 18% of cases.
  • Malignant and atypical meningiomas are less frequently encountered in the skull base than at the convexity
  • Ionising radiation can cause sphenoid meningiomas
  • Meningiomas en plaque of the sphenoid wing
    • More common in females
      • 77 and 94% of these growths are diagnosed in women

Clinical Presentation

  • Visual
    • Loss of vision, visual field cuts and optic atrophy.
    • Result from
      • Direct compression or encasement of the optic apparatus
      • Tumour growth into and around the optic foramen and canal.
    • Visual symptoms due to optic atrophy and intra-cranial hypertension may rarely be encountered in very large tumors.
    • Foster-Kennedy syndrome (ipsilateral optic atrophy and contralateral papilledema) has been traditionally associated with large meningiomas of the frontotemporal skull base.
  • Diplopia is not rare.
    • Due to
      • Tumor growth in the cavernous sinus or superior orbital fissure → ocular palsies.
      • Intraorbital tumor growth → restriction of ocular movements
  • CN V sensory loss
    • Due to
      • Involvement of the cavernous sinus
  • Prominent exophthalmos
    • Due to
      • Presence of intraorbital tumor,
      • Intraosseous growth in the lateral orbital wall and orbital roof
      • Venous stasis.
  • Cosmesis defect
    • Eg : Frontal and temporal bulging
    • Due to extracranial tumor growth and hyperostosis
    • Osseous involvement is often primarily a cosmetic problem.
  • Hemiparesis (and aphasia, if the dominant hemi-sphere is involved)
    • Can be encountered in patients with large tumors.
  • Cognitive and memory deficits, a flattened affect, and personality changes
    • Large tumours
  • Seizures
    • Relatively frequent.
    • Uncinate fits, and gustatory and olfactory hallucinations pointing to the temporal lobe as their origin are observed, as well as complex-partial and general-ized tonic-clonic seizures
  • Psychiatric symptoms
  • Clinical signs and symptoms reflect tumor location and growth pattern.
    • Tumors of the lateral sphenoid wing
      • Will often become relatively large before the development of a focal deficit such as hemiparesis or aphasia
      • Neuropsychological disturbances will often only become apparent in retrospect.
    • Tumors of the medial sphenoid ridge
      • Commonly cause earlier and more specific symptoms
      • Due to the proximity of the optic apparatus and cavernous sinus.
      • Patients with sphenoorbital meningiomas typically present with exophthalmos, deterioration of visual acuity and field cuts, and diplopia.
  • Tumour growth may extend into the facial and subcranial regions.
  • Asymptomatic
    • The number of patients with more or less asymptomatic meningiomas diagnosed during the course of a workup (e.g., for headache or vertigo) is increasing
    • But can have
      • Compression and encasement of the major arteries of the anterior circulation are clinically silent.
  • Some sphenoid ridge meningiomas (“sphenoorbital meningiomas”) are characterized by
    • Prominent bone invasion and hyperostosis involving the lateral orbital wall, the orbital roof, and eventually the orbit itself, resulting in cosmetic problems and exophthalmos, but also in compression of the optic nerve with subsequent loss of visual function.

Diagnostic workup

Ophthalmology review

  • Indication
    • Exophthalmos
    • Loss of vision or field cuts
    • Oculomotor palsies
    • Double vision
    • Whenever there is a risk that such deficits may be incurred during the surgery.

Plain x-rays

  • Thickening of the ala minor and the pterion (“smoking pterion”)
  • Allow for the diagnosis of sphenoid meningiomas in up to 90% of cases.
  • Historic interest

CT

  • Thin slices (e.g., 1 mm)
  • Bone window
    • Are necessary to show the extent of bone invasion
      • Particular importance for surgical planning in cases of en plaque and intraosseous meningiomas.

MRI

  • Contrast-enhanced T1-weighted sequences will usually delineate the soft tissue component of the tumour.
    • However, it is impossible to reliably differentiate invasion of dural layers at the margin of the solid portion of the tumour from adjoining neovascularization.
  • T2-weighted images (2 mm)
    • Delineate the course of the
      • Optic apparatus
      • Major vessels (i.e., the middle cerebral artery in cases of a meningioma of the lateral sphenoid wing, or the carotid artery and its major branches in patients with tumors of the medial ridge).
        • Obviate the need for formal digital subtraction angiography in most cases

Angiography

MRA or CTA
  • Delineate the course of major cerebral vessels
DSA
  • Delineate the course of major cerebral vessels
  • Test occlusion of the carotid artery if injury or sacrifice of this vessel is a possibility.
  • Preoperative embolization with polyvinyl alcohol particles or acrylic micro-spheres is used as an adjunct in some centers to reduce intraoperative blood loss
    • Comparative study no advantage of preoperative embolization could be demonstrated.
Blood supply
  • Meningiomas of the medial sphenoid ridge are usually fed by
    • Direct (sometimes intracavernous) branches of the internal carotid OR
    • Ascending pharyngeal artery
    • A recurrent branch of the ophthalmic artery passing through the superior orbital fissure.
  • Lateral tumours fed by
    • Superficial temporal artery
    • Middle meningeal artery
    • Additional feeding vessels may include the
      • Anterior meningeal artery
      • Other branches of the ethmoidal arteries.

Management

Conservative

  • Observe and watch
  • Even though virtually all patients with sphenoid meningiomas will still have to undergo surgery, the ability to follow asymptomatic residual tumor with serial neuroimaging, and the availability of efficient radiotherapeutic treatment have shifted the focus from curing sphenoid meningiomas toward symptom and growth control.

Surgery

Options depends on

  • Location of the tumour along the ridge (and in particular the corresponding arterial relations)
  • Extent of bone infiltration (e.g., with or without involvement of the orbital roof or the base of the middle fossa),
    • Bone involvement and en plaque tumours seem to be relatively common in outer 1/3 sphenoid wing meningiomas
      • Some have wide en plaque extension along the middle fossa which can be challenging to excise, especially in the proximity of the skull base neural exit foramina
      • Underlying hyperostotic bone has been shown in most cases to contain tumour cells within the bone lamellae and to achieve complete resection the inner table or the entire bone width, of if the outer table is also affected, should be drilled extradurally at the beginning of the resection.
      • To minimize the risk of recurrence very large craniotomy flaps are required and affected meninges ought to be resected.
  • Extent of dural involvement
  • Invasion of the cavernous sinus beyond the mere infiltration of its outer wall.
    • Large tumour may encroach upon the superior orbital fissure or the cavernous sinus, which will preclude a truly radical resection.
  • Involvement of medial neurovascular structures (can be fused with the meningioma and, rarely, even course within the tumour)
    • ICA branches
    • Proximal A1 and M1 segments
    • Optic nerve and chiasm
    • Oculomotor nerve
    • Pituitary stalk

Aim

  • Complete resection
    • Surgery will often cure the patient.
      • However, in other cases, extensive intraosseous growth and extension into the orbit and cavernous sinus will preclude a truly complete resection.
  • Relief of significant mass effect, decompression of the optic apparatus, and correcting a cosmetic deformity or exophthalmos.
    • If not possible for complete resection when there is extensive intraosseous growth and extension into the orbit and cavernous sinus

Surgical Technique

  • The surgical management of many meningiomas of the lateral and middle sphenoid wing is not very different from that of convexity tumors.
Lateral Sphenoid Ridge Meningiomas
  • Aims
    • Complete removal of the tumor
    • Excision of its dural origin, including a safety margin.
      • This will be possible in most cases and will conceptually cure the patient.
  • Approach
    • Frontotemporal craniotomy exposing the tumour and also any part of the dura invaded by the meningioma.
    • The pterion is drilled as required.
    • A carefully executed craniotomy provides early control of the tumour's main blood supply through dural and pterional branches of the external carotid meningeal artery.
    • Durotomy
      • Circumferential manner starting laterally. This results in further devascularization.
      • It may be helpful not to excise the mediobasal dura at this stage of the operation, even if it is involved by the tumour, to prevent undue epidural oozing into the surgical field.
    • Debulking
      • Cavitronic ultrasonic surgical aspirator (CUSA)
      • Small to medium-sized tumors may not require initial debulking
    • Disconnection
      • Identification and preservation of the distal branches of the middle cerebral artery.
        • Major branches of the middle cerebral artery and sometimes the main trunk itself may be engulfed by the tumor,
          • True invasion of the wall of the middle cerebral artery is very rare.
        • We try to identify the distal branches of the middle cerebral artery and follow them around or through the tumor.
          • This has proven much easier than attempting to dissect the proximal middle cerebral artery when there is still a substantial bulky tumor nodule left in the surgical field.
        • Dissecting the middle cerebral artery and its major branches from the capsule of the tumor, and identifying, coagulating, and dividing tumor-feeding vessels can be easy in patients with small tumors and preservation of an arachnoid plane
        • However, if the tumor has encased the middle cerebral artery or its branches, the preservation of these vascular structures may become very difficult.
          • A sharp scalpel can be very useful at this stage of the operation. One has to keep in mind that it is possible to tear the walls of major vessels, including the middle cerebral and the internal carotid artery, with the ultrasonic aspirator.
          • Finally, any remaining tumor nodules and tumor-infiltrated dura are removed.
        • If a particular part of the dura cannot be safely excised or is intentionally left behind (e.g., in cases with very large tumors extending medially and infiltrating the cavernous sinus) it is coagulated
    • Closure
      • Free pericranial grafts to obtain a reli-able watertight dural closure.
      • It is important to suture the graft onto the basal dura rather than its cut edges, allow-ing for a generous overlap of dura and graft. In addition, the suture can be sealed with fibrin glue. The bone flap
Middle Sphenoid Ridge Meningiomas
  • Removal of any bone overlying the tumor effectively turns many tumors of the middle ridge into “upside-down” convexity meningiomas
  • However, large tumors may extend far enough medially to involve the medial sphenoid wing, and surgery for such lesions may not be very much different from operations for medial sphenoid wing meningiomas.
  • Aim
    • Complete removal of the tumor, including any tumor-infiltrated bone and the tumor’s dural origin.
      • Intracranial tumor close to the optic apparatus should be resected aggressively because even a small regrowth can cause loss of vision and visual field defects, sometimes before an unequivocal mass can be visualized by magnetic resonance imaging (MRI).
        • On the other hand, visual symptoms and exophthalmos due to orbital involvement are often adequately treated by orbital decompression and limited intraorbital surgery.
    • Not possible
      • If involvement of
        • Cavernous sinus or
        • Extensive bony involvement and
        • Orbital growth (“sphenoorbital meningiomas”)
      • Then aim for
        • Long-term control of any globular intracranial component,
        • Relief and prevention of future compromise of the optic apparatus,
        • Good cosmesis.
  • Approach
    • Pterional craniotomy
      • Providing access to the orbital roof and the base of the middle fossa
      • The craniotomy has to be large enough to allow for the excision of any dural tumor carpet (en plaque growth).
    • A bicoronal incision
      • May be helpful in selected cases
      • Indicated if need for
        • Very large periosteal flaps,
        • Bilateral temporalis muscle fascia, or
        • Split calvarial grafts.
    • Any extracranial tumor extensions are excised, and the tumor-infiltrated bone is drilled extradurally.
    • The lesser wing of the sphe-noid is removed up to the level of the anterior clinoid process if needed.
    • The base of the middle cranial fossa can be resected up to the level of the foramen ovale, foramen rotundum, and foramen spinosum, providing access to the infratemporal fossa if needed.
    • Entry into the paranasal sinuses should be avoided
    • Other skull base approaches
      • Several variations of a combined pterional/frontotemporal and orbitozygomatic approach for large middle wing and in particular for sphenoorbital tumors can be used
      • Orbital and zygomatic osteotomies may be added to a conventional pterional approach, allowing for a more direct exposure of the lateral orbital wall and the middle fossa.
      • Skull base approaches, however, carry their own approach-related morbidity, and several large series report good neurological, resection, and cosmetic outcomes after surgery for sphenoorbital meningiomas without the routine use of skull base techniques.
    • Some middle ridge tumors may involve the anterior clinoid process and the optic canal.
      • Extradural clinoidectomy and unroofing of the optic canal have been advocated for such cases to prevent additional damage to an already com-promised optic apparatus during the intradural dissec-tion.
      • We and others feel that extensive extradural drilling may even increase the risk for optic nerve damage due to the retraction necessary for these maneuvers.
  • How to deal with arteries
    • Clinoidal meningiomas
      • Have a tendency to encase the origin of the ICA
        • In most cases an arachnoidal plane is present between the tumour and surrounding neurovascular structures, but some meningiomas are adherent to the adventitia and some residual tumour may have to be left behind.
    • The large arteries of the anterior circulation may be engulfed by large tumors, involving the medial sphenoid wing.
      • In such cases early visualization of the internal carotid artery is sometimes impossible.
    • Start vascular dissection laterally (i.e., we identify distal branches of the middle cerebral artery in the sylvian fissure) and follow them medially until one reaches the main trunk of the middle cerebral (and eventually the internal carotid) artery.
    • It is important to consider and spare the lenticulostriate branches as these are the most vulnerable.
    • After the large tumor bulk has been removed, it is often possible to expose the hidden proximal carotid artery from a subfrontal route and to dissect the remaining tumor away from the vessel, alternating between a proximal and a distal/lateral approach
  • How to deal with optic apparatus
    • Use neurophysiology: visual evoked potentials
    • Developing proper (arachnoidal) dissection planes is very important.
    • Inappropriate retraction, tearing of feeding vessels, and even bipolar coagulation in the vicinity of an already impaired optic nerve or chiasm can result in further deterioration.
    • Frequently there is extension into the superolateral segment of the optic canal which should be explored in cases with visual compromise even if not readily visible on preoperative imaging. If the ipsilateral optic nerve and chiasm is surrounded by tumour, a sub frontal trajectory to identify the contralateral optic nerve, again, helps decompression of the chiasm and optic nerve in a retrograde fashion thus facilitating the preservation of its blood supply which is predominantly via the superior hypophyseal arteries.
    • In general, surgery for recurrent tumours is much more demanding (and carries increased complication rates) due to the absence of arachnoidal planes. This is an important argument for aggressive initial surgery.
    • Of note, the optic apparatus is a radio-sensitive structure, and even if the patient will undergo radiosurgery anyway, one of the crucial goals of surgery is to gain as large a distance as possible between any residual tumor and the optic nerve and optic chiasm.
  • Cavernous sinus infiltration
    • Infiltration of the cavernous sinus is seen in a sizable proportion of large or en plaque middle sphenoid wing meningiomas.
    • Cavernous sinus involvement varies from being in the
      • Lateral wall to
      • Extensively within the sinus (‘holocavernous’)
    • The outer layer of the wall of the cavernous sinus can be resected.
    • Intracavernous tumor is nowadays frequently, and many say probably best, left behind.
    • Surgery for cavernous sinus meningiomas has met with limited success.
    • Sindou et al have reported a series of 100 cases with cavernous sinus meningiomas, including 40 patients who had surgery within the cavernous sinus it-self
      • Persistent palsies of cranial nerves III, IV, and VI were seen in 26 to 33%, and trigeminal nerve dysfunction in 31% in this latter subgroup.
      • Only 12 patients had a gross total resection of their tumor
    • Intracavernous tumour should be treated with SRS rather than microsurgery in all but a few patients with ophthalmoplegia.
  • Orbital extension
    • Tumour in the superior orbital fissure, the annulus of Zinn, and the apex of the orbit in general should not be resected aggressively.
    • The periorbita can be stripped if necessary.
    • Outright tumor-infiltrated periorbita can be resected.
    • Opening the periorbita is only necessary in the rare case of nodular intraorbital tumor growth.
    • Tumor growth will usually be restricted to the superior or lateral parts of the orbita.
    • Any intraorbital tumor is removed under meticulous avoidance of the intraorbital nerves and extraocular muscles. It is important to keep the extra-ocular muscles grossly intact, even if that entails leaving some tumor behind.The need for orbital reconstruction continues to be debated.
    • Orbital reconstruction
      • Is thought to prevent
        • Enophthalmos
        • A pulsating eye
        • Oculomotor muscle fibrosis
      • Supraorbital rim margin needs to be preserved (or reconstructed, if violated).
      • Reconstruction of the orbit has been advocated if more than one of its walls has been resected.
      • Good clinical results after only minimal cranioorbital reconstruction (e.g., with methylmethacrylate, Gelfoam and fibrin glue)
      • All reconstructive procedures may interfere with postoperative surveillance imaging.

Surgical Outcomes

Variable recurrence and complication rates after surgery for sphenoid ridge meningiomas have been reported.
  • Due to
    • Different growth patterns and degrees of resectability of the various types of sphenoid meningioma
    • Different treatment philosophies.
  • As already pointed out, one can argue that surgery for many tumors with extensive bony involvement and cavernous sinus infiltration aims at symptom control and improvement rather than cure.
  • Assessing the degree of resection is not easy
    • Current neuroimaging cannot distinguish reliably between Simpson resection grades I, II, and III.
    • Residual dural tumour cannot be reliably delineated by MRI scanning.
    • The extent of the bony resection is best appreciated on postoperative CT scans.
Virtually all globular lateral wing meningiomas, the great majority of globular tumours of the middle sphenoid ridge, and many small to medium-sized medial wing tumours show only limited bone infiltration and no cavernous sinus involvement.
  • Such tumours can be resected completely, including their dural origin, conceptually curing the patient.
  • Recurrence rates should not exceed the figures seen in convexity meningiomas, that is, 5 to 10%.
Recurrence rates after operations for medial wing tumours and for hyperostosing/enplaque meningiomas will be higher.
  • Recurrence rates of
    • 9 to 23% for medial wing tumours,
    • 8 to 31% for sphenoorbital meningiomas.
Surprisingly significant mortality and morbidity rates after meningioma surgery in general have been reported in unselected series.
  • Two recent American studies including 15,028 and 1281 patients, respectively,
    • Mortality rates of 2.3% and 6%,
    • Complication rates ranging from 4.5% to 16.5%.
  • Complication rates after operations for intracranial meningiomas vary considerably with the location and the size of the tumor and patient-dependent factors such as age and comorbidities.
    • Increasing tumor size correlates with peritumoral oedema, pial vascularization of the tumor, and ultimately a failure to maintain an extrapial dissection plane, resulting in cortical damage and sometimes vascular injuries.
    • Operations for globular tumours of the middle and outer third of the sphenoid wing probably carry complication rates very similar to those for surgery for convexity tumors.
      • Morokoff et al recently reported a surgical series of 163 cases of convexity meningiomas with 0% mortality, new neurological deficits in 1.7%, and an overall complication rate of 9.4%.
    • Complication rates after surgery for medial sphenoid wing meningiomas are higher.
      • Visual deterioration, aphasia, and hemiparesis may occur in up to 5 to 10% of patients.
        • On the other hand, visual dysfunction may improve after surgery in 40 to 85%.
    • Sphenoorbital meningiomas
      • > 30% chance of visual improvement following operations
      • Visual deterioration, new diplopia, and significant trigeminal symptoms may be seen in > 5 to 10% of patients.
      • Cosmesis after surgery for sphenoorbital tumors, despite their often extensive bony involvement, is usually quite acceptable.
      • Skull base approaches may carry a higher risk for postoperative temporomandibular joint dysfunction, trigeminal neuralgia/hyperpathia, and adverse cosmetic outcomes.

Radiotherapy

Indication

  • Residual tumor after meningioma surgery
    • If residual tumour size
      • <30-35mm
        • Follow patients with serial imaging.
        • Radiosurgery is initiated if the tumor remnant has demonstrably enlarged.
      • >30 to 35 mm
        • Start with radiosurgery after the 3-month follow-up MRI scan has been obtained.
    • No evidence indicating that early radiotherapy is better than deferring radiotherapy until tumor progression.
  • Unresectable progressive disease.

Outcome

  • Progression-free survival after fractionated radiotherapy is ~90% at 5 years and 80 to 90% at 10 years for benign meningiomas.
  • The corresponding figures for stereotactic radiotherapy and radiosurgery are even slightly better.
  • These numbers reflect both the efficacy of meningioma radiotherapy and the natural history of the disease.
  • The 5-year progression-free survival rate was 60% in a series of 38 patients with petroclival meningiomas who had a subtotal resection and no postop-erative radiotherapy.
  • Tumor size and the vicinity of the optic apparatus often limit radiotherapeutic options for sphenoid wing meningiomas.
  • Only 69% of the patients with sphenoid wing meningiomas reported by Nutting and coworkers had no progression at 10 years following mostly subtotal surgery and fractionated radiotherapy.
  • Results for other skull base locations were better, and the authors felt that these differences were most likely due to the on average larger size of the sphenoid meningiomas in their study.
  • Surgical decompression of the optic chiasm and optic nerves may be a prerequisite for successful radiotherapy of sphenocavernous meningiomas.
  • Cavernous sinus disease in general is a good indication for radiosurgery or stereotactic radiotherapy.
  • Data exist that suggest that radiotherapy may help to control residual intraorbital meningioma.
  • Radiosurgery and stereotactic radiotherapy are important additions to the neurosurgical armamentarium. However, aggressive surgery is still appropriate in many cases.
    • A conservative operation followed by radiotherapy for a challenging tumor may result in a patient 10 years older with a progressive and unresectable tumor, and few remaining therapeutic options.
  • The risk of the formation of radiation-induced cancers may be an underappreciated concern, especially in younger patients.