ESTRO 2024 - Abstract Book

S673

Clinical - Breast

ESTRO 2024

We conducted a retrospective analysis of 105 breast cancer patients who underwent treatment between 2022 and 2023 at our Department. All patients received treatment to the right breast, with 20% also receiving ipsilateral regional nodal irradiation (RNI). For each patient, we delineated Organs at Risk (OARs) and Planning Target Volumes (PTVs) in the FB CT scans, and subsequently re-optimized the treatment plans. Dosimetric parameters, including Lungs V 20 Gy , Lungs V 10 Gy , Lungs V 5 Gy , Liver Dmax, Heart Dmax, and Heart V 5Gy , were collected for each plan. To account for differing schedules and dose per fraction, all data were converted and reported in EQD2 using an α/β ratio of 4 [4]. Statistical analysis was performed using Wilcoxon signed-rank tests, with statistical significance defined as p < 0.05.

Results:

The majority of treatments were administered using Intensity-Modulated Radiation Therapy (IMRT) (80%) and Volumetric-Modulated Arc Therapy (VMAT) (20%). Two distinct irradiation schedules were employed: 5 fractions (40%) and 15 fractions (60%). The maximum liver EQD2 dose (LMD) was 10.8 Gy with FB compared to 3.0 Gy with DIBH (p < 0.001). The mean lung dose (MLD) was 5.0 Gy with FB versus 2.8 Gy with DIBH (p = 0.002). Additionally, V 20Gy of the right lung was 7.4 Gy with FB versus 4.7 Gy with DIBH (p < 0.02), and V 5Gy was 14.9 Gy with FB versus 9.9 Gy with DIBH (p = 0.005). However, the benefit of DIBH was not found to be statistically significant for maximum lung and heart doses.

Conclusion:

To our knowledge this is the first large population study evaluating DIBH for right breast cancer irradiation. The dosimetric analysis shows that DIBH, when compared to FB, reduces Liver Dmax, Lung Mean-Dose, right-Lung V 20 Gy and right-Lung V 5Gy . Further investigations are warranted to elucidate the precise patient profiles that benefit the most from right DIBH and to answer the question whether DIBH is needed for all right-sided breast cancers.

Keywords: Right DIBH, dosimetric benefit

References:

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