3D-Conformal versus Intensity modulated radiation therapy in the treatment of early stage glottic squamous cell carcinoma: A dosimetrical analysis

Background: The objective of this study is to dosimetrically compare and 
contrast both techniques in the treatment of early stage glottic squamous cell 
carcinoma as regards the planning dose volume (PTV) dose coverage and the 
doses perceived by the organs at risk particularly the thyroid gland, carotid 
arteries and spinal cord.
Methods: Twenty patients with the pathological diagnosis of early glottic SCC 
(T1-T2/N0) were enrolled in the study design during the period October 2022 
till January 2023. All patients were treated in Kasr Elainy center of clinical 
oncology using 3D-CRT radiotherapy technique. A dose of 66Gy in 33 fractions 
was the prescribed dose to the planning target volume (PTV). An intensity 
modulated radiotherapy (IMRT) plan was done for each patient and the 
dosimetric parameters were contrasted to the 3D-CRT plan 
Results: The homogeneity index (HI) for PTV66Gy was higher for the IMRT 
plans with a value of 0.1± 0.005 as contrasted to 0.08 ± 0.006 for the 3D-CRT 
plans with a statistically significant p-value of 0.002. The IMRT plans showed z 
significantly superior PTV95% coverage with values of 98.3 ± 14.7 as opposed 
to 94.5 ± 30.7 for the 3D-CRT plans (p-value of 0.003). The dose received by 
the thyroid gland was lower in the IMRT group with a value of 14.9Gy ± 5.39 
compared to 51.2Gy ± 8.62 for the 3D-CRT plans with a statistically significant 
p-value of 0.004. Mean doses to the right and left carotid artery were lower in 
the IMRT plans compared to the 3D-CRT plans (p-value of 0.201& 0.266).
Conclusion: In early glottic cancer, the plans generated by IMRT showed a 
better PTV coverage and more homogeneous dose distribution when compared 
to the plans achieved by 3D-CRT. The IMRT plans showed better OAR sparing 
with respect to the thyroid gland and carotid arteries.