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Proton Beam Radiosurgery Paranasal Sinus Tumors

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Proton Beam Radiation for Advanced Paranasal Sinus Tumors by Allan Thornton, MD, MGH Radiation Oncology and Michael Joseph, M.D., MEEI Otolaryngology
Stephen B. Tatter,M.D., Ph.D., HTML editor

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The first of a series of new protocols for treatment of advanced head and neck malignancies has been introduced to the RTOG (Radiotherapy and Oncology Group) by the Massachusetts General Hospital and Massachusetts Eye and Ear Infirmary. This hyperfractionated, accelerated fractionation trial is currently in progress for patients with advanced malignancies of the paranasal sinuses. This aggressive regimen builds on the MGH experience in hyperfractionation to include the increased targeting accuracy of proton therapy, hoping to spare patients morbid-, extensive-surgical resections of the orbital contents and maxillary area.Patients are treated over a 6.5 week period with 3-dimensionally planned photon irradiation in the morning, followed at least 6 hours later by proton irradiation designed to spare the dose-limiting structures of optic nerves, chiasm, and brainstem.

The rationale for selection of paranasal sinus tumors derives from the relatively sparse lymphatic drainage pattern of this anatomic area; therefore, tumors of this area are late to develop metastatic disease and may rep resent a category of head and neck tumors for whom increased local control may translate into increased suivival. Statistical predictions based upon dose-response data from pharyngeal wall tumors (similar in metastatic rate and growth patterns) suggest that a dose increase from current standards of 65 Gy to 75 Gy may result in as much as a 35% increase in local control.

The use of proton therapy for advanced head and neck tumors incorporates 15 years of experience with high-dose precision fractionated particle radiotherapy for the treatment of skull-base sarcomas at the MGH in cooperation with the Harvard Cyclotron Laboratory. The ability to target beams more precisely with 3-dimensional software specifically designed for particle therapy, as well as the ability to control the depth of proton beam penetration is unique to particle beam irradiation. It is now possible to deliver irradiation with the precision of single dose radiosurgical techniques developed for "gamma-knife" and stereotactic radiosurgical programs for AVM therapy, but with greater uniformity of irradiation throughout the volume treated. This improved uniformity is critical to the safe efficacious irradiation of critical structures (chiasm, optic nerves, brainstem). The reproducible immobilization systems utilized now render it possible to fractionate this therapy over 6.5 weeks in a practical fashion with daily treatments of 20 minutes.

Figure 4a: Coronal MR showing intracranial invasion by esthesioneuroblastoma in a 38 year old woman.
Figure 4b: Coronal MR showing intracranial view, same patient, 16 months later after chemotherapy, craniofacial resection and proton beam radiation.

This program has accrued 24 patients thus far, including 2 currently under treatment. Despite the complexity of treatment planning involved, we have been able to maintain the same timetable for post-operative treatment as for conventional planning, i.e. commencing irradiation within 4 weeks following limited surgery. Permanently implanted cranial fiducials, in concert with improved cranial immobilization using both thermoplastic masks and full denture prostheses, have resulted in daily positioning inaccuracies of less than 0.5mm. Because of this patient set-up accuracy, we have been able to treat tumors in close approximation to the visual system (optic nerves and chiasm) to radical (curative) doses, while maintaining standard radiation tolerance to these structures.

Toxicity has included the expected acute moist desquamation and nasal crusting. The increased targeting accuracy implicit in proton therapy has resulted in significantly less oral mucositis than realized with conventional therapy, as well as improved salivary and gustatory functions. Nasal crusting has been severe, due to the increased doses delivered. One patient developed a mucocutaneous fistula through an area of skin with vascular compromise and tumor infiltration.

For additional information or patient referral please contact:
Dr. Michael P. Joseph, Department of Head and Neck Oncology, Massachusetts Eye and Ear Infirmary (617 593-3192) or Dr. Allan F. Thornton, Department of Radiation Oncology, Massachusetts General Hospital (617 724-1156).

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