Optimizing Contralateral Breast Sparing: A Comparative Study of Single- versus Dual-PTV Configuration Across Modern Radiotherapy Techniques

Abstract

Background: In breast cancer radiation therapy, target delineation strategy and treatment technique significantly influence the treatment quality and organ at risk sparing.

Objectives: This study aimed to compare dosimetric outcomes between single and double planning target volume PTV approaches using three-dimensional conformal radiotherapy and volumetric modulated arc therapy.

Methods: Ten breast cancer patients were retrospectively re-planned using the four-planning strategy and techniques per patient. Plans were assessed in relation to Planning target cover, Homogeneity index, Conformity index, Monitor unit, Hotspots, other PTV doses, and contralateral breast as a sensitive organ at risk. Data were extracted from the DVH dose-volume histogram.

Results: The results found that all planning strategies efficiently covered PTV, whereas double PTV planning demonstrated improved dose distribution compared with single PTV in both techniques. In the 3DCRT technique, the separation of PTVs significantly reduced contralateral breast dose (p = 0.021). Similarly, the VMAT technique showed a statistically significant reduction with double PTV planning (p = 0.002). However, VMAT plans delivered significantly higher contralateral breast doses compared with 3DCRT in both single and double PTV approaches (p < 0.001). Whereas VMAT provided improved homogeneity and conformity to the target, it was associated with increased low-dose spread to surrounding normal tissues.

Conclusion: Double PTV planning enhances dose optimization and improves contralateral breast sparing in both 3DCRT and VMAT techniques. Although VMAT offers superior target conformity, 3DCRT demonstrates better protection of the contralateral breast. Careful selection of target segmentation strategy and technique is essential to balance target coverage and contralateral breast sparing in breast radiotherapy.