Objective:

To compare dosimetric differences between anatomical landmark-based and glandular tissue-based approaches for clinical target volume (CTV) delineation in postoperative breast cancer radiotherapy, highlighting the significance of these differences.

Key Findings:

• CTVgl volumes were significantly smaller than CTVan volumes (432.87 cc vs. 582.59 cc; P < 0.001) in a study of 48 patients.
• Glandular-based delineation resulted in lower Dmax, higher D98, and reduced exposure to organs at risk.
• Significantly lower left lung V20, mean heart dose, heart V40, and contralateral breast Dmean in the CTVgl group (P < 0.001).
• CTV volume positively associated with heart and contralateral breast dose.

Interpretation:

Glandular tissue-based delineation produced smaller target volumes and lower radiation exposure to adjacent organs compared to anatomical landmark-based delineation, suggesting potential benefits for patient safety.

Limitations:

• Clinical implications of dosimetric reductions cannot be inferred from this analysis alone; further studies incorporating normal tissue complication probability (NTCP) modeling and clinical outcomes are needed.

Conclusion:

Glandular tissue-based delineation offers dosimetric advantages over anatomical landmark-based delineation, but further research is required to assess long-term clinical relevance and implications for treatment decisions.