Improved Outcomes For Patients Treated With Neutron Radiotherapy And Gamma Knife For Salivary Gland Neoplasms With Base Of Skull Invasion

James Douglas1, Aaron Kusano1, Upendra Parvathaneni1, Jay Liao1, Mark Phillips1, George E. Laramore1, Robert Goodkin1

1University of Washington, Seattle/ USA

Keywords: cancer, radiotherapy, skull base, salivary gland, gamma knife

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Abstract

       Malignant skull base tumors can pose great management challenges.
     Our purpose was to evaluate the effect on local control and survival of a Gamma Knife boost added to Neutron radiotherapy for salivary gland neoplasms with base of skull invasion.
     Patients had the following characteristics: median age 54; female: male ratio 1.4:1; all had TNM stage III or IV disease; 95% had evidence of gross residual disease. Sites of disease included: parotid -26; nasopharynx - 31; paranasal sinuses - 50; oral cavity- 15; oral pharynx -2; lacrimal gland- 6; auditory canal- 3; miscellaneous sites - 5. Histologies included: adenoid cystic carcinoma 114; adenocarcinoma 8; mucoepidermoid 8; squamous cell carcinoma 2; basaloid 1; other carcinomas NOS 5.
     One-hundred thirty eight patients having salivary gland neoplasms with base of skull invasion were treated with neutron radiotherapy ± Gamma Knife boost at the University of Washington. All patients were treated with neutron radiotherapy with a neutron dose of 18.4 – 19.2 nGy. 6Sixty-two patients were treated with neutron radiotherapy while the remaining 76 were treated with the addition of a Gamma Knife boost (median dose 12 Gy to 50% isodose line; median isocenters 18; median treated volume 13.9 cm3, median conformity index 1.6; and median target coverage of 96%). The median follow-up for the entire group was 25.5 months; non-boosted group 28.5 months and 24 months for the GK boosted group. 
     The Kaplan Meier (KM) 5-year projected local control of the non-GK boosted patients was 17 months. The KM 5-year projected local control of the GK boosted group was 62% (p = 0.001). The median time to failure in the non-boosted group was 18 months. The median time to failure in the GK boosted group has not been reached. The KM estimated overall 5-year survival was 71% in the boosted group compared to 14% in the non-boost group (p = 0.05). Side effects were similar in both groups with the exception of temporal lobe changes found on T2 MRI in over 50% of patients in the boosted group. The majority of patients with MRI changes were asymptomatic.
     This was a retrospective study
     A GK boost added to Neutron radiotherapy for patients having salivary gland neoplasms with base of skull involvement markedly improves 5-year local control and survival with acceptable complications.
     A GK boost added to Neutron radiotherapy should be the recommended therapy for such patients.


Acknowledgements

Project Roles:

J. Douglas (), A. Kusano (), U. Parvathaneni (), J. Liao (), M. Phillips (), G. Laramore (), R. Goodkin ()