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Background: Parotid gland malignancies are very rare and constitute less than 1 percent of all cancers. Fast neutrons are effective in controlling locally advanced salivary gland malignancies, though their use has often been associated ith high expense of facilities and high toxicity rates. Most investigators have studied salivary gland malignancies as a cluster despite their variable location in the head and neck region due to the paucity of patients. For radiotherapy this can be undesirable as the organs at risk may vary per sub-site. The outcomes of treatment of salivary gland malignancies of the sub-site parotid ith neutron radiotherapy ere then studied in an attempt to refine patient selection for this modality. Methods: Records of patients ith unresectable parotid gland malignancies treated ith neutron radiotherapy at Tygerberg HospitaliThemba Laboratory for Accelerator Based Sciences LABS in Cape Ton beteen January 1991 and December 2012 ere revieed. Tenty-to patients ere eligible for statistical analysis. All patients but 1 received 20.4 Gy for 4 5 eeks. Treatment planning as 3D conformal. Results: Median time to local control as 4 months. Locoregional control at 2 years as 80 percent CI 41-95 and at 5-, 10- and 15- years as 69 percent CI 30 -89 . Overall survival at 2 years as 40 percent CI 18 61 and at 5-, 10- and 15- years as 35 percent CI 14 56 . Unresectable disease had a significant negative influence on survival compared to macroscopic residual p = 0.02, HR 6.7 CI 1.23 36.30 here as inoperable disease did not p = 0.81, HR 1.2 CI 0.18 - 9.1 . The severe toxicity rate CTCAE grade 3 and above as 9 percent. Conclusions: Subsite study does reveal different outcomes hen compared to global studies. The locoregional control outcomes of treatment of sub-site parotid trend are better but overall survival is poorer. The toxicity rate appears to be loer for this sub-site study than for global studies. Neutron radiotherapy for sub-site parotid is both efficacious and safe.,J Clin Oncol 34, 2016 suppl; abstr e17566 ,Publication Only Head and Neck Cancer
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