Preliminary Simulation Study of Carotid Artery and Pharyngeal Constrictor Muscle Sparing-Radiotherapy in Glottic Carcinoma

Abstract

Background: This preliminary simulation study aimed to compare the dosimetric outcomes of carotid arteries (CAs) and pharyngeal constrictor muscle (PCM) in patients with T1N0M0 glottic carcinoma undergoing helical tomotherapy-intensity modulated radiotherapy (HT-IMRT) and 3-dimensional conformal radiotherapy (3D-CRT) plans. Methods: In addition to the clinical target volume (CTV) which was defined as the entire larynx, the CAs and PCM of 11 glottic carcinoma patients were delineated. The CTV was uniformly expanded 5 mm to create a planning target volume (PTV) relative to the PCM and at a distance of 2 mm from the CA. The dosimetric characteristics in HT-IMRT and lateral opposed fields-based 3D-CRT plans were analyzed. Results: Median D95%and V100% of PTV were significantly higher in HT-IMRT (p < 0.001) compared to 3D-CRT. The right/left CA dosimetric outcomes, including the mean doses (20.7/21.5 Gy versus 48.7/50.5 Gy), Dmax (53.6/52.0 Gy versus 67.4/67.7 Gy), V30 (25.0/27.1% versus 77.6/80.3%), V40 (8.0/7.9% versus 74.6/71.9%), and V50 (2.0/1.2% versus 70.0/71.6%) were also significantly lower in HT-IMRT (p < 0.05), similar to the mean PCM doses (49.6 Gy versus 62.6 Gy for 3D-CRT;p < 0.001), respectively. Conclusions: Our present results demonstrated the feasibility of simultaneous sparing of the CAs and PCM in HT-IMRT- compared to 3D-CRT plans in glottic carcinoma patients undergoing definitive radiotherapy.

Accelerated three‐dimensional conformal radiotherapy for early‐stage glottic cancer in reducing dose to the internal carotid artery and pharyngeal constrictor muscles

“…1 Typically, radiotherapy for ESGC is performed using parallelopposed lateral portals (POLP). 2 However, the organs at risk (OARs), such as the bilateral internal carotid arteries (CAs) and pharyngeal constrictor muscle (PCM), frequently receive doses that are equivalent to that prescribed to the target, potentially leading to the development of stenosis of the CAs and dysphagia when the target dose coverage is prioritized over the OARs. 3,4 Some facilities have reported the use of threedimensional conformal radiotherapy (3D-CRT) with two anterior oblique portals (AOP) to reduce the dose to the OARs.…”

“…Radiotherapy is pivotal in definitively treating early‐stage glottic cancer (ESGC) with favorable curability 1 . Typically, radiotherapy for ESGC is performed using parallel‐opposed lateral portals (POLP) 2 . However, the organs at risk (OARs), such as the bilateral internal carotid arteries (CAs) and pharyngeal constrictor muscle (PCM), frequently receive doses that are equivalent to that prescribed to the target, potentially leading to the development of stenosis of the CAs and dysphagia when the target dose coverage is prioritized over the OARs 3,4 .…”

Comparison of Carotid Artery Dose in Early-Stage Glottic Cancer Treated with 3D-Conformal, Helical-IMRT and VMAT

“…Radiation therapy (RT) and surgery are both viable treatment options, but there is no conclusive evidence that one is superior as a single modality of treatment [2] . Local RT alone for early glottic cancer has shown 5-year local control rates of 80%-90% [1][2][3][4] . Therefore, there is an opportunity to customize RT delivery specifically to the glottic target in these patients, as the glottic subregions of the larynx are considered low risk for regional or distant metastasis due to their minimal vocal cord lymphatic drainage system [2,3] .…”

“…Therefore, attention to carotid dose reduction through advanced conformal RT techniques is necessary. The relationship between radiation and injury to carotid arteries (CAs) is well established, and survivors of head and neck carcinomas undergoing neck irradiation have reportedly increased transient ischemic attacks and stroke [3][4][5][6][7] .…”

“…In addition to the risk of cerebrovascular events, high radiation doses to CAs may impact the re-irradiation of patients with second primary head and neck malignancies or neck recurrences due to the potential risk of CA injury or hemorrhage [4,6] . New radiation techniques, such as intensity-modulated RT (IMRT), have demonstrated the ability to reduce CA doses to lower levels without negatively impacting the target dose coverage in patients with early-stage laryngeal carcinoma [4,9,10] .…”