Maxillary Antrum

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Radical en bloc resection of the tumor is the initial treatment of choice if possible. Contraindications include extension of disease to the nasopharynx, base of skull, pterygoid fossa and distant metastases.

T1 lesions are limited to the antral mucosa with no erosion or destruction of bone. A partial maxillec-tomy, usually through a lateral rhinotomy, is performed, removing the tumor in an en bloc fashion. Postoperative radiation therapy is indicated except for early, locally confined, well-differentiated squamous cell carcinomas where surgery alone is sufficient.

T2 lesions involve bone erosion or destruction, except for the posterior antral wall, and include extension into the hard palate and/or the middle nasal meatus. These are treated with a total maxil-lectomy and en bloc resection of tumor usually through a Weber-Ferguson approach. Surgery alone is sufficient for early, locally confined well-differentiated squamous cell carcinomas. Otherwise, postoperative radiation therapy is indicated, as the ability to achieve good clear surgical margins is most difficult. Treatment would be administered within 6 weeks after the procedure using conventional frac-tionation to a total dosage of 6,300 cGy using three-dimensional conformal treatment planning.

T3 lesions are extensive and involve the bone of the posterior wall of the maxillary sinus, subcutaneous tissues, skin of the cheek, floor or medial wall of the orbit, the infratemporal fossa, the pterygoid plates and the ethmoid sinuses. If these can be approached surgically, a total maxillectomy with an en bloc resection of all involved structures is performed. Postoperative radiation therapy is adminis tered in a fashion similar to that described above. A combined modality approach would provide better local control than either treatment alone.

T4 lesions represent massive disease and involve invasion of the orbital contents beyond the floor or medial wall, including the orbital apex, cribriform plate, base of skull, nasopharynx, sphenoid and frontal sinuses. Occasionally these may be resectable through the use of a craniofacial approach. Postoperative radiation therapy would be indicated in the fashion described above.

For resectable lesions, the indications for postoperative radiation therapy include: (1) T3 and T4 disease, (2) positive or close margins, (3) perineural/ vascular invasion and (4) the surgeon's concerns regarding adequacy of resection (eg, tumor spillage, piecemeal resection, margins status irrespective of the pathology report).

There are no prospective trials comparing preop-erative versus postoperative radiation therapy for paranasal sinus tumors. Retrospective studies show no clear advantage of one approach over the other.

5-year survival rates are in the 25 to 30 percent range with single treatment modalities.80 A combined modality approach using surgery and postoperative radiation therapy produces somewhat improved results with local control rates of 50 to 60 percent and 5-year survival rates of 40 to 50 percent.81

At Memorial Sloan-Kettering Cancer Center, we prefer postoperative radiation therapy using three-dimensional conformal treatment planning based on a heavily weighted AP portal and right/left lateral opposed portals (Figure 21-11). We are investigating the use of intensity modulated radiation therapy in selected cases. The treatment volume would include the total nasal cavity, complete ethmoid sinuses, partial or subtotal frontal sinuses, sphenoid sinus, nasopharynx, hard palate, the ipsilateral maxillary antrum and the medial aspect of the contralateral maxillary antrum. The incidence of lymph node metastasis is relatively low at 15 to 20 percent and therefore elective nodal irradiation is not performed. Postoperatively, conventional fractionation is used delivering 180 cGy per fraction to a total dosage of 6,300 cGy if possible. Because of the close proximity of vital structures such as the brain stem, orbits, optic nerves, optic chiasm and spinal cord, special

Figure 21-11. Computer-generated three-dimensional conformal treatment plan for a maxillary antrum tumor using two lateral portals with wedges and an anterior portal.

attention must be paid to evaluating the dose given to these areas and this may modify the total dosage administered.

In selective cases, neoadjuvant radiation therapy with or without chemotherapy can be considered for initially unresectable or only marginally resectable lesions. Conventional fractionation at 180 cGy per fraction to a total dosage of 4,500 to 5,400 cGy is administered to try and cause tumor shrinkage and thus possibly improve resectability.

Advanced unresectable disease can be considered for treatment with chemotherapy and radiation therapy. Complex three-dimensional conformal treatment planning is used to produce fields described above. At Memorial Sloan-Kettering Cancer Center, we would administer cisplatin chemotherapy on days 1 and 22 concurrent with radiation therapy using accelerated fractionation with a delayed concomitant boost to a dosage of 7,000 cGy. The use of neutrons has been reported with 30 percent 3-year survival rates.82

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