Radiotherapy for the treatment of pituitary adenomas: A dosimetric comparison of three planning techniques

Rubi Ramos-Prudencio; Sandra Ileana Pérez-Álvarez; Christian Haydée Flores-Balcazar; Mayra Angélica de León-Alfaro; José Alfredo Herrera-González; Jonathan Elizalde-Cabrera; Johnatan Rubalcava-Ortega; Lissett Espinoza-Alvarado; Ricardo Iván Balderrama-Ibarra

doi:10.1016/j.rpor.2020.04.020

Radiotherapy for the treatment of pituitary adenomas: A dosimetric comparison of three planning techniques

Rep Pract Oncol Radiother. 2020 Jul-Aug;25(4):586-593. doi: 10.1016/j.rpor.2020.04.020. Epub 2020 May 19.

Authors

Rubi Ramos-Prudencio¹, Sandra Ileana Pérez-Álvarez¹, Christian Haydée Flores-Balcazar¹, Mayra Angélica de León-Alfaro¹, José Alfredo Herrera-González², Jonathan Elizalde-Cabrera², Johnatan Rubalcava-Ortega³, Lissett Espinoza-Alvarado³, Ricardo Iván Balderrama-Ibarra⁴

Affiliations

¹ Department of Radiotherapy, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Vasco de Quiroga 15, Belisario Domínguez, Sección XVI, Tlalpan, México City 14080, Mexico.
² Division of Radiotherapy, Instituto Nacional de Cancerología, 22 San Fernando Ave, Sección XVI, Tlalpan, México City 14080, Mexico.
³ Department of Neuroimaging, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Salvador Zubirán, Vasco de Quiroga 15, Belisario Domínguez, Sección XVI, Tlalpan, México City 14080, Mexico.
⁴ Department of Radiotherapy, Instituto Mexicano Del Seguro Social (IMSS), Centro Médico Nacional de Occidente, Universidad de Guadalajara, Independencia Oriente, Guadalajara 44340, Mexico.

Abstract

Aim: Our goal was to compare conformal 3D (C3D) radiotherapy (RT), modulated intensity RT (IMRT), and volumetric modulated arc therapy (VMAT) planning techniques in treating pituitary adenomas.

Background: RT is important for managing pituitary adenomas. Treatment planning advances allow for higher radiation dosing with less risk of affecting organs at risk (OAR).

Materials and methods: We conducted a 5-year retrospective review of patients with pituitary adenoma treated with external beam radiation therapy (C3D with flattening filter, flattening filter-free [FFF], IMRT, and VMAT). We compared dose-volume histogram data. For OARs, we recorded D2%, maximum, and mean doses. For planning target volume (PTV), we registered V95%, V107%, D95%, D98%, D50%, D2%, minimum dose, conformity index (CI), and homogeneity index (HI).

Results: Fifty-eight patients with pituitary adenoma were included. Target-volume coverage was acceptable for all techniques. The HI values were 0.06, IMRT; 0.07, VMAT; 0.08, C3D; and 0.09, C3D FFF (p < 0.0001). VMAT and IMRT provided the best target volume conformity (CI, 0.64 and 0.74, respectively; p < 0.0001). VMAT yielded the lowest doses to the optic pathway, lens, and cochlea. The position of the neck in extreme flexion showed that it helps in planning mainly with VMAT by allowing only one arc to be used and achieving the desired conformity, decreasing the treatment time, while allowing greater protection to the organs of risk using C3D, C3DFFF.

Conclusions: Our results confirmed that EBRT in pituitary adenomas using IMRT, VMAT, C3D, C3FFF provide adequate coverage to the target. VMAT with a single arc or incomplete arc had a better compliance with desired dosimetric goals, such as target coverage and normal structures dose constraints, as well as shorter treatment time. Neck extreme flexion may have benefits in treatment planning for better preservation of organs at risk. C3D with extreme neck flexion is an appropriate treatment option when other treatment techniques are not available.

Keywords: C3D, conformal three-dimensional radiotherapy; CFRT, conventional fractionated radiotherapy; CI, conformity index; CT, computed tomography; CTV, clinical target volume; Conformal radiotherapy; DVH, dose-volume histogram; EBRT, external beam radiation therapy; ESAPI, Eclipse Scripting Application Programming Interface; FF, flattening filter; FFF, flattening filter free; GTV, gross tumor volume; HI, homogeneity index; IMRT; IMRT, modulated intensity radiotherapy; MRI, magnetic resonance imaging; OAR, organs at risk; PTV, planning target volume; Pituitary adenomas; RION, radiation-induced neuropathy; RT, radiotherapy; SRS, stereotactic radiosurgery; VMAT; VMAT, volumetric modulated arc therapy.