Dosimetric Study Comparing 3D Conformal Radiotherapy (3D-CRT) and Volumetric Modulated ARC Therapy (VMAT) for T3 & T4 Squamous Cell Glottic Cancer

Abdellatif Ennakri

Objectives--- The standard of care for radiation treatment of early larynx cancers has been conventional treatment using opposed lateral fields encompassing the larynx and overlying neck structures, including the adjacent carotid arteries. While intensity-modulated radiotherapy (IMRT) has replaced conventional radiotherapy for all other head/neck cancer situations, the use of IMRT to treat early glottic cancers remains controversial. In this work, we compared Conformal External beam radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT) plans for T3 & T4 stage squamous cell glottic cancer in terms of dosimetric features as target volume coverage (PTV), dose to the organs at risk (OAR) and also total monitor unit (UM). Methods: In this, study 8 patients with T3- T4squamous cell glottic cancer. Conformal External beam radiotherapy (3D-CRT) using 6 field, two arcs for volumetric modulated radiotherapy (VMAT), was planned for each patient. The prescribed dose was 50 Gy in 25 fractions. The minimum dose for 95% of the clinical target volume D95%, the maximum dose point at clinical target volume Dmax, the near dose point for 2% of clinical target volume D2%, the near dose point for 5% of clinical target volume D5%, the minimum dose for 98% of the clinical target volume D98%, conformity index CI, homogeneity index HI. Spinal cord, PRV Spinal cord and brainstem (maximum doses), left and right parotid gland (dose mean –percentage of volume receiving 30Gy), and total monitor unit calculated for each plan. Data entry was done on Excel software and static analysis by SPSS software version 21.0. Results: The dose maximal of the planning target volume was lower with VMAT® (p <0.001).This technique allowed better parotids sparing in terms of mean dose and for the volume of (V30<50%) with (p <0.001).Better also for spinal cord, PRV spinal cord sparing and for 1cc of Mandibule (p <0.001). MUs in VMAT® are more much important than conformational radiotherapy (3D) (p <0.001) wich influence the treatment time, 4,5min for VMAT® and 3,5min for 3D. Conclusion: The technique of RCMI (VMAT) reduce the radiation dose to the parotids gland and spinal cord compared with 3D conformal radiotherapy (3D-CRT), but with more UM and a relatively longer processing time. Such a results assists in decreasing the incidence of radiation induced Xerostomia, thus improving the quality of life for patients. Advances in Knowledge Morocco is a country in the process of development in the field of cancer treatment by radiotherapy and in the context of establishing and using high technicality, our center has taken this challenge to switch from 3D-CRT to IMRT and the VMAT. My study focuses on the enhancement of the VMAT technique in the treatment of laryngeal cancer as well as its benefits for high-risk organs, especially parotidsgl and in order to avoid xerostomi in patients and to maintain their quality of life.

Volume 12 | 03-Special Issue

Pages: 327-331

DOI: 10.5373/JARDCS/V12SP3/20201268