PAROTID-GLAND SPARING IN PATIENTS UNDERGOING BILATERAL HEAD AND NECK IRRADIATION - TECHNIQUES AND EARLY RESULTS

Purpose: To minimize xerostomia in patients receiving bilateral head a nd neck irradiation CRT) by using conformal RT planning to spare a sig nificant volume of one parotid gland from radiation. Methods and Mater ials: The study involved 15 patients with head and neck tumors in whom bilateral neck radiation was indicated. The major salivary glands and the targets (tumor, surgical bed, metastases to lymph nodes, and the locations of lymph nodes at risk for metastases) were outlined on axia l computed tomography images. Beam's-eye view (BEV) displays were used to construct conformal beams that delivered the prescribed doses to t he targets while sparing from direct radiation most of one parotid gla nd. The gland that was planned to be spared resided in the neck side t hat was judged in each patient to be at a lesser risk of metastatic di sease. Major salivary gland how rates and the responses to a subjectiv e xerostomia questionnaire were assessed before, during, and after rad iation. Results: Radiation planning for patients,vith central orophary ngeal tumors required the generation of multiple axial nonopposed beam s. The resulting isodoses encompassed the targets, including the retro pharyngeal nodes and the jugular nodes up to the base of skull bilater ally, while limiting the dose to the oral cavity, spinal cord, and one parotid gland. For patients with lateralized tumors, the ipsilateral neck side was treated up to the base of the skull; in the contralatera l neck side, the treatment included the subdigastric nodes but exclude d the jugular nodes at the base of the skull and most of the parotid g land. This was accomplished by a moderate gantry angle that was chosen using the BEV displays. Three months following the completion of radi ation, the spared parotid glands retained on average 50% of their unst imulated and stimulated hows. In contrast, no saliva how was measured from the unspared glands in any of the patients. Subjective xerostomia was absent, mild, or not different from that reported before radiatio n in 10 of 15 patients (67%). Conclusion: Partial parotid gland sparin g is feasible by using three-dimensional planning in patients undergoi ng bilateral head and neck radiation. Approximately 50% of the saliva how from the spared glands may be retained, and most patients thus tre ated have no or mild xerostomia in the early period after the completi on of radiation. Whether tumor control and late complications are comp arable to standard radiation will be assessed as more experience is ga ined.