Impact of Seroma Volume Reduction on Dosimetry in Whole Breast Radiation Therapy: A Case Study and Adaptive Planning Considerations

Aims: To explore the impact of seroma volume reduction on dosimetry during whole breast radiation therapy (WBRT) and evaluate the significance of adaptive planning.

Presentation of Case: A 71-year-old female with left breast invasive carcinoma underwent lumpectomy and radiotherapy. An initial CT (CT1) six weeks taken post-op showed a seroma cavity, and a second CT (CT2) five weeks later documented a 65% seroma volume reduction (from 217 c.c. to 75 c.c.). Five radiotherapy techniques were evaluated: two-field conventional, three-field conventional, forward IMRT, inverse IMRT, and VMAT. Inverse IMRT and VMAT achieved better high-dose coverage and reproducibility but had larger dose variations. They also showed higher maximum doses and increased hot spot volumes, indicating potential overdosage risks. Conventional techniques provided stable lower-dose coverage but less uniform high-dose distribution compared to IMRT and VMAT.

Discussion: The significant reduction in seroma volume affected dosimetry, highlighting the importance of adaptive planning. In this case, daily KV and weekly MV imaging were used for alignment, but CBCT may better monitor seroma changes. Adaptive radiotherapy, repeated CT simulations, and CBCT are essential for effective treatment. Further research should focus on improving treatment precision through advanced imaging and radiotherapy technologies.

Conclusion: This single WBRT case highlights the dosimetric impact of seroma reduction and the importance of imaging and adaptive strategies. Advanced techniques like inverse IMRT and VMAT improve precision but need careful IGRT monitoring. These findings emphasize the need for individualized adaptive planning considerations and further research to optimize protocols for managing seroma volume changes during WBRT.