Can carotid-sparing radiotherapy approaches replace with conventional techniques for the patients with T1 glottic larynx cancer?

OBJECTIVES: This study aims to compare the carotid artery doses applied with various radiotherapy techniques for the treatment of T1N0 glottic larynx cancer.

PATIENTS AND METHODS: Five patients were simulated with using computed tomography (CT). Clinical (CTV) and planning target volumes (PTV) were created for T1N0 glottic larynx cancer. Planning risk volumes (PRV) were constructed for carotid arteries and spinal cord. Three irradiation planning, opposed lateral box field (OLBF), three dimension conformal radiation therapy (3DCRT), intensity modulated radiation therapy (IMRT) were done for each patient. Over 95% of planned target volumes were loaded with predetermined dose (a total of 62.25 Gy of 2.25 Gy daily dose).

RESULTS: The comparison of the treatment planning of five T1 glottic larynx cancer, three involving the right vocal cord and two involving the left vocal cord, the technique of IMRT planning was provided the best carotid-sparing doses. Mean carotid V35, V50, and V63 values including OLBF, 3DCRT, and IMRT were 70%, 47%, 35%; 55%, 15%, 5% and 28%, 6%, 0%, respectively. The statistical comparison of V35, V50 and V63 revealed significant values for OLBF and IMRT. Dose of spinal cord did not exceed 45 Gy for any of radiation treatment planning. Between the three techniques, there was no significant difference in terms of conformity index and dose distribution was homogenous with all techniques.

CONCLUSION: It is obvious that IMRT planning technique can decrease the carotid artery radiation doses in early stage glottic larynx cancer.