ESTRO 2024 - Abstract Book

S6026

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

Mouna Ben Rejeb, Ghada Abdessatar, Rim Moujahed, Rihab Haddad, Awatef Hamdoun, Lilia Ghorbal, Lotfi Kochbati

Abderrahman Mami Hospital, Radiotherapy, Ariana, Tunisia

Purpose/Objective:

The proximal carotid artery (CA) may be exposed to high doses of radiation, when treating supraclavicular area in patients with node-positive disease.

The purpose of our study was to assess the doses to (CA) among three dimensional conformal radiotherapy (3DCRT) and volumetric modulated arc therapy (VMAT) and to investigate the feasability of carotid sparing volumetric modulated arc therapy (CS VMAT).

Material/Methods:

Twenty-five patients who were treated with 3DCRT were selected. They all received irradiation to level III and IV lymph nodes in addition to chest-wall/breast, using a mono-isocentric technique. The prescription dose was 40.05 Gy delivered in 15 daily fractions of 2.67 Gy ± an additional boost of 13.35 Gy to the tumor bed. The CA was retrospectively delineated. DICOM data were used to create the virtual CS-VMAT plans for each patient. The parameters used for comparison of planning were mean (Dmean), maximum doses (Dmax) and V40 for carotid artery.

Results:

The median age was 43 years [24-70 years]. Cardiovascualar risk factors were noted in 28% of cases.

When the CA was considered as organ at risk for CS-VMAT planning, the median of V40 was decreased to 1,97% from 19,18% compared to 3DCRT plans (p = 0.052).

The median of the Dmean to the CA was significantly higher for 3DCRT plans than for the CS-IMRT plans (25,74 Gy versus 16,23 Gy, p=0,0001).

No difference was obtained between the plans in terms of the Dmax parameter.

Conclusion:

Our findings showed that CS-VMAT resulted in good target coverage and provided significant sparing of the CA as compared to conventional 3DCRT technique. This has the potential to decreases the incidences of stroke and other cerebrovascular events and maintain the same local control rates.

Keywords: breast cancer, radiotherapy, carotid artery