Radiation Oncology: A Question-Based Review

Sinonasal Tract Tumors

Boris Hristov and Gopal K. Bajaj

image Background

What is the incidence of sinonasal tract (SNT) tumors in the U.S.?

~2,000 cases/yr of SNT tumors (<1% of all tumors)

Is there a gender predilection for SNT tumors?

Yes. Males are more commonly affected than females (2:1).

SNT tumors are more common in what continents?

SNT tumors are more prevalent in Asia and Africa.

What histologies are typically seen with SNT tumors?

Squamous (most common), melanoma, adenocarcinoma, adenocystic, esthesioneuroblastoma (ENB), sarcoma (rhabdomyosarcoma), lymphoma, plasmacytoma, and mets

What nonmalignant entities present as a mass in the paranasal sinuses (PNS) or the nasal cavity?

Sinonasal polyposis, choanal polyps, and juvenile angiofibromas all present as a mass in the SNT.

What sinuses make up the PNS?

The frontal, ethmoid, sphenoid, and maxillary sinuses make up the PNS.

What structures border the maxillary sinus?

1.     Anterolateral: facial bone

2.     Superior: orbital floor

3.     Inferior: hard palate

4.     Medial: nasal cavity

5.     Posteromedial: infratemporal fossa

What is the name for the thin bone in the medial wall of the orbit that is prone to erosion/breakthrough by ethmoid tumors?

The thin bone of the medial orbital wall is called the lamina papyracea.

What is the local invasion pattern of ethmoid tumors?

Superiorly through the cribriform plate to the ant cranial fossa or medially through the lamina papyracea into the orbit

Which is the most common sinus/site of origin for SNT tumors?

The maxillary sinus is the most commonly involved sinus/site for SNT tumors (70%–80%).

What is the most common site for ENB?

The nasal cavity is the most common site for ENB.

What environmental exposures are associated with the development of SNT tumors?

Thorotrast, nickel, chromium, hydrocarbons, nitrogen mustard, and wood dust (500 times risk for maxillary sinus tumor)

image Workup/Staging

What are some presenting Sx of SNT tumors?

Facial pain, epistaxis, sinus obstruction, trismus (pterygoid involvement), ocular deficits (diplopia, blurry vision), facial pain due to trigeminal neuralgia, midfacial hypesthesia from impingement of the infraorbital branch of CN V, palatal mass/erosion, and otalgia

What is the basic workup for SNT tumors?

SNT tumor workup: H&P, labs, CT/MRI head/neck, Bx, and CT C/A/P

Describe the T staging of maxillary tumors per the latest AJCC classification.

1.     T1: confined to sinus, no bone erosion

2.     T2: bone erosion without involvement of post wall of maxillary sinus or pterygoid plate

3.     T3: invasion of post wall of max sinus, pterygoid fossa, floor/wall of orbit, ethmoid sinus

4.     T4a: invasion of ant orbital structures, skin of cheek, pterygoid plate, infratemporal fossa, cribriform plate, sphenoid or frontal sinus

5.     T4b: invasion of orbital apex, nasopharynx, clivus, intracranial extension, CN involvement (except V2)

How are the nodes staged for SNT tumors?

1.     N1: single, ipsi, <3 cm

2.     N2a: single, ipsi, 3–6 cm

3.     N2b: multiple, ipsi, ≤6 cm

4.     N2c: bilat or contralat ≤6 cm

5.     N3: >6 cm

How are the overall SNT stage groups broken down (based on TNM)?

1.     Stage I: T1N0

2.     Stage II: T2N0

3.     Stage III: T3N0 or T1-3N1

4.     Stage IVA: T4aN0-2 or T1-3N2

5.     Stage IVB: T4b or N3

6.     Stage IVC: M1

What is the T stage for a maxillary tumor with involvement of the pterygoid plate vs. the pterygoid fossa?

1.     Pterygoid plate involvementT4a

2.     Pterygoid fossa involvementT3

What are the 2 most important prognostic factors for SNT tumors?

Clinical staging and the relationship of tumor to the Ohngren line

What is the Ohngren line, and why is it important?

The Ohngren line is a theoretic plane that extends from the medial canthus of the eye to the angle of the mandible. Tumors anteromedial to this plane have a better prognosis b/c of better surgical resection rates. Tumors superopost to this have deeper invasion, with many being unresectable (due to invasion of the orbit, ethmoids, and pterygopalatine fossa).

For SNT tumors, what factor predicts for nodal mets?

Neck nodal involvement is rare at Dx except when tumors have progressed to involve the mucosal surfaces (i.e., oral cavity, maxillary gingiva, or gingivobuccal sulcus).

What neck node groups are generally involved with SNT tumors?

Level Ib or II, retropharyngeal (1st echelon), and periparotid nodes are most commonly involved.

What subsite of SNT tumors has the highest rate of nodal mets?

Maxillary sinus tumors have the highest rate of nodal mets (10%–15%) of all SNT tumors.

What is the 5-yr OS rate for maxillary/ethmoid sinus tumors (all stages)?

The 5-yr OS rate for all stages of SNT tumors is ~45%

What is the 5-yr OS rate for N+ maxillary sinus tumors?

The 5-yr OS rate for N+ maxillary sinus tumors is <10%.

What is the 5-yr OS rate for nasal cavity tumors (all stages)?

The 5-yr OS rate for all stages of nasal cavity tumors is ~60%.

What is the overall LC rate for SNT tumors?

The overall LC rate is 50%–60%.

image Treatment/Prognosis

How are SNT tumors typically managed?

Surgical resection and adj RT +/− chemo. Consider induction chemo in sinonasal undifferentiated carcinomas or in very advanced primary squamous carcinomas.

What type of surgery is necessary to manage a maxillary sinus tumor?

Partial (2 walls of maxilla removed) or total maxillectomy to –margins. For smaller medial tumors, a medial maxillectomy with a midfacial degloving technique is performed with an incision made under the lip. For larger tumors, access through the nasal crease/upper lip may be necessary. Reconstruction is done with skin grafting and obturator placement.

How are ethmoid sinus tumors managed surgically?

Ethmoid sinus tumors are surgically managed by craniofacial resection, requiring access both anteriorly through the sphenoethmoid area (through the nose) and superiorly with a craniotomy (neurosurgery) to address the skull base/dura.

When is orbital exenteration necessary in SNT tumors, and when is it not absolutely necessary?

It is necessary if periorbital fat or extraocular muscles are involved. It is not necessary if there is only bone erosion.

What are some nonadj indications for radio-therapy in the management of SNT tumors?

For inoperable tumors (medically and technically), early-stage tumors (T1-2N0), to preserve the eye, or preoperatively to downstage tumors before resection

What are the indications for adj radiotherapy after resection of SNT tumors?

Maxillary sinus T3-T4 lesions, ethmoid sinus T1-4 lesions (NCCN), N+, +margins, +PNI, adenoid cystic histology

How is radiotherapy delivered and to what dose?

IMRT, FSR, or SRS approaches, to 70 Gy (definitively) or 63–66 Gy (adj), 50–54 Gy to low-risk areas. Use image fusion (MRI/CT) for planning purposes.

Per the NCCN, what altered RT fractionation regimens can be employed for maxillary sinus tumors?

Per the NCCN:

1.     Accelerated (6 fx/wk during wks 2–6): 70 Gy for gross Dz and >50 Gy for subclinical Dz

2.     Concomitant boost (bid last 2 wks): 72 Gy over 6 wks (1.8 Gy/fx large field and 1.5 Gy/fx same-day boost over last 2 wks)

3.     Hyperfractionated: 1.2 Gy/fx bid to 81.6 Gy over 7 wks

Is concurrent chemo a standard approach in the definitive management of SNT tumors with RT?

No. Prospective trials are evaluating CRT, and it can certainly be considered (e.g., for advanced/unresectable or N+ Dz).

For which tumors should elective neck management be considered (with surgery or RT)?

Elective neck management should be considered for maxillary sinus tumors. It may be left out for other subsites with N0 Dz.

When should the neck be treated for ethmoid sinus tumors?

The neck should be treated if Nor with extrasinus involvement (skin, muscle). The retropharyngeal nodes need to be covered.

What study/data supports the use of ENI for maxillary sinus tumors?

Stanford data (Le QT et al., IJROBP 2000): 97 pts (36 RT alone, 61 surgery + RT), 12% nodal failure overall in levels I–II; 5-yr nodal failure risk 20% −ENI, 0% +ENI; 5-yr distant relapse rate 29% with neck control, 81% if neck failure

What data supports the use of 3D conformal vs. 2D planning in the Tx of SNT tumors with RT?

Brizel et al. (Radiother Oncol 1999) and Gabriele et al. (Tumori 2008) demonstrated lower doses to the optic nerves, eye, and chiasm with 3D planning techniques; however, there was no impact on survival.

What have recent studies demonstrated regarding the use of adj IMRT for SNT tumors?

There was no significant improvement in terms of LC or OS; however, there was a lower incidence of complications with IMRT. (Daly ME et al., IJROBP 2007Madani I et al., IJROBP 2009)

image Toxicity

What is the RT dose tolerance of the retina?

The RT dose tolerance of the retina is ~45–50 Gy.

What is the RT dose tolerance of the optic chiasm?

The RT dose tolerance of the chiasm is 50–54 Gy.

What is the RT dose tolerance of the parotids?

The RT dose constraints for the parotids are as follows: mean dose <26 Gy or V30 Gy <50%.

What is the RT dose tolerance of the lacrimal gland?

The RT dose tolerance of the lacrimal gland is <26–30 Gy, similar to that of other glands (e.g., the parotids).

Describe the recommended follow-up schedule for pts treated for SNT tumors.

SNT tumor follow-up (per the NCCN): H&P (q1–3mos for yr 1, q2–4mos for yr 2, q4–6mos for yrs 4–6, and q6–12mos thereafter), baseline CT/MRI after Tx and regular chest imaging if indicated clinically, TSH every 6–12 mos if neck RT