endoscopic resection of malignant sinonasal tumours: current … · 2014-06-05 · important to...

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For citation purposes: Dmytriw AA, Witterick IJ, Yu E. Endoscopic resection of malignant sinonasal tumours: current trends and imaging workup. OA Minimally Invasive Surgery 2013 Sep 19;1(1):3. Co

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Endoscopic resection of malignant sinonasal tumours: current trends and imaging workup

AA Dmytriw1, IJ Witterick2, E Yu3*

AbstractIntroductionModern advances in endonasal en-doscopic surgery have expanded its utility in the management of ma-lignant sinonasal tumours, and the degree to which cases are eligible. Knowledge of the indications, inclu-sion and exclusion criteria and imag-ing workup that empowers judicious patient selection is essential. This ar-ticle discusses the endoscopic resec-tion of malignant sinonasal tumours.ConclusionStudies describing the impact of pa-tient quality of life will surely affect the fate of endoscopic resection, but the current trend suggests that this technique stands to replace an open approach when outcomes are similar. Combined craniofacial/endoscopic and craniofacial-only approaches to sinonasal malignancy remain an im-portant option in the management of complex disease.

IntroductionOver the past two decades, advances in endonasal endoscopic surgery in terms of both experience and tech-nology have expanded its efficacy in the management of malignant sinon-asal tumours1. While an external

approach remains the gold stand-ard for resection of these tumours, undesirable morbidity can include facial incision and scarring, the need for craniotomy or facial bone oste-otomy, surgical complications, longer hospitalisation period and slower recovery. When applicable, brain retraction with associated encepha-lomalacia and oedema can also be avoided2,3.

Traditional external approaches seek to achieve an en bloc resection of all involved bone and soft tissue with negative histopathological margins, most commonly via the techniques of lateral rhinotomy or midface deglov-ing4. Should the cribriform plate or fovea ethmoidalis be involved by the superior extent of the tumour, ante-rior craniofacial resection is typically required5. The goal in any approach is to adequately expose the nasal cav-ity, while preserving function and cosmesis for the patient.

Purported advantages of techni-cal advances in endoscopic resection, particularly with the advent of angled endoscopes, include the ability to navigate difficult anatomic corners, with the subsequent provision of su-perior tumour visualisation. As op-posed to en bloc removal, endoscopic resections sometimes require piece-meal removal of tumour. Due in part to this difference, concern has his-torically been raised about the ability to achieve clear margins comparable to open approaches (e.g. lateral rhi-notomy plus anterior craniotomy). Surgical margins are one of the strongest predictors of disease con-trol, and thus this remains a critical factor in the assessment of evolv-ing techniques6,7. Advances in tu-mour imaging, surgical techniques,

appropriate patient selection and the ability to apply combined en-doscopic/craniofacial approaches to difficult cases have increased the utility of transnasal endoscopic sur-gery. The aim of this review is to dis-cuss the current trends and imaging workup of endoscopic resection of malignant sinonasal tumours.

DiscussionThe authors have referenced some of their own studies in this review. These referenced studies have been conducted in accordance with the Declaration of Helsinki (1964), and the protocols of these studies have been approved by the relevant ethics committees related to the institution in which they were performed. All human subjects, in these referenced studies, gave informed consent to participate in these studies.

Current indicationsEndoscopic management of na-soethmoidal malignancies with or without involvement of the adjacent anterior skull base or orbital inva-sion has been shown to be an appro-priate indication for pure endoscopic or cranioendoscopic surgery, with careful patient selection8.

An endoscopic approach should be considered for tumours which oc-cupy the central nasal cavity between the frontal and sphenoidal sinuses but do not extend to the lateral la-mella of the pterygoid bone. Tumour invasion of the nasal bones, anterior/posterior table of the frontal sinus or frank orbital invasion are considered contraindications. Posteriorly, it is important to assess invasion of the ca-rotid and cavernous sinus. If tumour is noted tracking along nerves (most

* Corresponding author Email: [email protected] Department of Medical Imaging, University

of Toronto, 101 College St, University Health Network, Toronto, ON, M5G 1L7, Canada

2 Department of Otolaryngology-Head & Neck Surgery, University of Toronto, 190 Elizabeth Street, Room 3S-438, R. Fraser Elliott Build-ing, University Health Network, Toronto, ON, M5G 2N2, Canada

3 Department of Medical Imaging, University of Toronto, 610 University Ave, Princess Mar-garet Hospital, University Health Network, Toronto, ON, M5T 2M9, Canada

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tumour of the naso-ethmoidal com-plex through a purely endoscopic approach is also contraindicated as is extensive involvement of the lac-rimal pathways, extension through orbital contents, the superior and lat-eral aspects of the frontal sinus and the floor of the nasal cavity. Patients with involvement of the medial wall of the maxilla and the medial por-tion of the posterior wall are often excellent candidates for endoscopic resection. However, involvement of the superior, anterior, inferior and lateral walls may require conversion to an open approach. Involvement of the brain or other extension which would require resection of the ante-rior cranial fossa dura lateral to ap-proximately the mid-orbital roof is also contraindicated.

Standard imaging testsThe main role of imaging in the setting of sinonasal malignancy is to identify malignant disease, its anatomical extent and any meta-static lymphadenopathy. Radiologi-cal findings suggestive of malignancy include bony involvement (erosion and destruction), a soft tissue com-ponent, a unilateral disease pro-cess and soft tissue necrosis with or without lymphadenopathy20. The clinician should be aware of factors which are associated with particu-larly poor patient prognosis, such as tumour encasement of the carotid artery, extension to involve the peri-orbita or dura, cavernous sinus inva-sion and perineural tumour spread. Metastatic lymphadenopathy is sug-gested by the presence of nodal clus-tering, rounded shape, inhomogene-ity on contrast-enhanced studies and peripheral spread, all in the context of a plausible drainage pathway21. These factors are essential determi-nants in the planning of endoscopic surgery and potential postoperative radiation when applicable.

When tumours occur in the maxil-lary or ethmoid sinuses, the American Joint Commission on Cancer T-category

Inclusion and exclusion criteriaSingle olfactory bulb resection, such as in olfactory neuroblastoma, is challenging with a standard crani-ofacial approach, and thus an en-doscopic approach is proposed as the preferred method of resection. However, contralateral olfactory bulb salvage is currently rare. In addition, these patients are only eligible in the absence of intraorbital or intracra-nial involvement, which underscores the importance of appropriate pa-tient selection. In cases such as these where clear margins will be challeng-ing, endoscopic resection should be avoided.

Endoscopic resection of sinonasal tumours that are centrally located in the nose and sinuses should be con-sidered before the external approach is used. While adenocarcinoma, ol-factory neuroblastoma, squamous cell carcinoma, adenoid cystic carci-noma and malignant melanoma are the most frequent indications for en-doscopic surgery, it remains unclear which tumour types are most appro-priate given anatomically favourable positions. An endoscopic approach is also recommended for surgical biop-sies of tumours which penetrate into the sphenoid sinus from the sella, the petrous apex and/or adjacent areas18.

Unfortunately, there are still no criteria which absolutely indicate whether a sinonasal malignancy is resectable by endoscopic means. Generally, however, tumours that demonstrate invasion of the cavern-ous sinus are associated with signifi-cant patient morbidity and should not be approached endoscopically. In addition, transdural extension is a relative contraindication for both open and endoscopic resection. In some cases, such as optic chiasm in-vasion, these tumours are not resect-able by any means4,19.

Other contraindications to a pure endoscopic approach include ex-tension into facial and orbital soft tissues. Resection of a malignant

importantly trigeminal), these are also relative contraindications to an endoscopic approach. Tumour can be resected from the periorbita, but the tumour-invading ocular muscle will typically require orbital exen-teration and thus an open approach. Endoscopic orbital exenteration has been described but is not widely practiced3,9. Malignant tumour types that have been resected with favour-able results include adenocarcinoma, adenoid cystic carcinoma, chordoma, malignant melanoma, olfactory neu-roblastoma, osteosarcoma and squa-mous cell carcinoma9–12.

In many situations, a lateral rhi-notomy incision and craniotomy can be avoided by endoscopic resec-tion of the extracranial portion of a sinonasal malignancy with transcra-nial resection at the anterior skull base2,13. In such cases, margins of the mucosa, periorbita and dura should be microscopically clear to ensure local control on par with open tradi-tional approaches. A number of stud-ies have shown that locally advanced malignancy across a variety of his-topathological types can be treated endoscopically1,14,15. However, long-term data are lacking in terms of a direct comparison between open and endoscopic techniques. If the tu-mour extends lateral to the midpoint of the orbital roof, typically by way of dural spread, it becomes difficult to resect. Moreover, the dural recon-struction is challenging, leading to higher rates of cerebrospinal fluid (CSF) leak in the postoperative pe-riod. As a result, open craniotomy is combined with endoscopic resection to avoid lateral rhinotomy12,13. As ro-botic surgery and 3D high-definition endoscopy technologies advance, it is anticipated that these boundaries and the capabilities for skull base re-construction will both improve.

Lastly, endoscopic sinus surgery has also achieved acceptance in the management of epistaxis and nasal obstruction in the palliative setting of sinonasal malignancy16,17.

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dramatically fallen in most centres. A study of 800 endonasally treated patients revealed a CSF leak rate of 15.9%, in which all but one case was treated successfully with re-peat endonasal endoscopy or lumbar drainage28. These data are favourable for endoscopic over external resec-tion, though the majority of the tu-mours in the study were benign.

A large series of malignant sinona-sal tumours treated with pure endo-scopic (72.8%) or cranioendoscopic (27.2%) techniques involving 184 patients showed a 5-year disease-specific survival of 91.4% and 58.8% respectively. The authors conclud-ed that while operator experience is a significant factor, endoscopic

and 94% specificity in the identifica-tion of jugular vein and venous sinus invasion26.

Treatment outcomes Morbidity and mortality are signifi-cant concerns with both craniofacial-only and combined craniofacial/endoscopic resection, including but not limited to meningitis, encepha-lomalacia/oedema, pneumocepha-lus, trismus, blindness and bone flap necrosis4,15,27. However, the most common serious complication is CSF leak, and contemporary advances in endoscopy have yielded rates com-parable with open resection. With the advent of the vascularised na-soseptal flap, CSF leak rates have

is applied to imaging findings22. Com-puted tomography (CT) represents the best modality with which to assess for the presence of bony remodelling or bony invasion, for example of the sinus walls, orbital margins and the floor of the anterior cranial fossa (Figure 1). Coronal and axial views are essential for complete assessment of the ptery-goid plates, maxillary sinus, ethmoid bullae and sinus and sphenoethmoid recess. Magnetic resonance imaging (MRI) is an important tool for the as-sessment of bone marrow invasion, where the high T1 signal fatty marrow is replaced by that of tumour20,23. Dis-placement of the periorbita is typically diagnosed on CT, with a reported NPV of 86% and PPV of 75%24. The essen-tial orbital finding is invasion beyond the periorbita (i.e. fat, muscle) as peri-orbital invasion can be approached endoscopically, but involvement of the fat or muscle will usually neces-sitate orbital exenteration (Figure 2). MRI is also valuable in the assess-ment of dural involvement and brain invasion. The former is evidenced by focal thickening and enhancement of the dura. Brain invasion is suggested by the presence of both brain oedema and parenchymal enhancement and cortical disruption (Figure 3).

Purely endonasal resections with-in the frontal sinus are also limited by the lesion laterality. Using the the modified Lothrop procedure, the floor of the frontal sinus can be removed to approach tumours. How-ever, this is typically limited to those tumours which have extended into the sinus with minimal or no bony involvement. Tumour occupying the frontal sinus is often heterogene-ously enhancing on a gadolinium T1 sequence. Vascular encasement and nerve involvement, best identified with MRI, are also contraindications to pure endoscopic resection, but a combined external and endoscopic approach may facilitate circum-ferential dissection around these structures23,25. Last, MRI has been shown to have a 100% sensitivity

Figure 1: Sagittal CT bone algorithm image of a squamous cell carcinoma in the ethmoid sinus (asterisk) that has eroded the overlying floor of the anterior cranial fossa.

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approaches15. In their study of 120 patients, where the most common site of tumour origin was the nasal cavity (52%), positive margins were present in 15% of patients and the 5- and 10-year disease-specific survival rates were 87% and 80%, respective-ly. Recurrence rates did not differ be-tween the two groups. Encouragingly, CSF leak occurred in 3% of patients and was also not significantly differ-ent between the groups. It is notable that in both studies, the proportion of olfactory neuroblastoma was high, as these are often associated with good prognosis for 5–10 years be-fore possible recurrence. In addition, the proportions of patients in either treatment group were not necessar-ily matched for disease stage.

Last, there is great theoretical benefit for elderly patients under-going resection of sinonasal malig-nancies. Outcome of craniofacial resection in patients 70 years of age and older are significantly worse in terms of mortality, complication and disease-specific long-term sur-vival29. Given that elderly patients often do not tolerate brain retrac-tion well, pure endoscopic resection stands to improve outcomes in this population.

ConclusionEndoscopic techniques are being em-ployed with increasing frequency in the setting of sinonasal malignancy. In order to best utilise this approach, appropriate patient selection is es-sential. Concurrent advances in MRI are poised to assist in the discrimi-nation of surgical candidates, par-ticularly with improved detection of perineural and vascular involvement.

As international trials continue, long-term follow-up and further insight into oncologic outcomes will become apparent, ideally with disease-specific data. Additional in-formation about the potential for improved quality of life will undoubt-edly be a major determinant in the future use of endoscopic resection.

Figure 2: Coronal T1- (a) and T2 (b)-weighted images show an ethmoid sinus carcinoma that has disrupted the periorbita along the right medial orbital wall. Note the normal appearance of the periorbita on the left side which appears as a smooth curvilinear black line (white arrows in (b)). On the affected side, the black outline is attenuated and more irregular in contour. However, (a) still shows preservation of the orbital fat (arrow in (a)) and the rectus musculature.

Figure 3: Two coronal T2-weighted images of a patient with an ethmoid squamous cell carcinoma taken approximately 2 months apart. Note the breach of the normal black cortical outline of the ethmoid roof and cribriform plate. (a) Evidence of dural thickening and irregularity compatible with dural invasion (white arrow in (a)). (b) A new contiguous tumour involvement of the inferior grey matter/cortex of the right orbital gyrus (white arrow in (b)) and new oedema in the adjacent white matter (dashed arrow in (b)).

management of malignancies eligible for either external or endoscopic re-section is an equally efficacious alter-native to an external approach1. The largest US study to date addressing

pure endoscopic (77.5%) and cranioendoscopic (22.5%) resec-tion of malignant tumours corrobo-rated the assertion that oncological outcomes are acceptable with these

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Combined craniofacial/endoscopic and craniofacial-only approaches to sinonasal malignancy remain an im-portant option in the management of complex disease.

Abbreviations listCSF, cerebrospinal fluid; CT, comput-ed tomography; MRI, magnetic reso-nance imaging.

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