Effect of RTOG breast/chest wall guidelines on dose-volume histogram parameters

Area of Science:

• Radiation Oncology
• Medical Physics
• Oncology

Background:

• Traditional breast cancer treatment planning relies on clinical landmarks.
• Radiation Therapy Oncology Group (RTOG) established consensus guidelines for contouring target volumes (TV) including breast/chest wall and draining lymphatics.
• The dosimetric impact of RTOG guidelines on organs at risk (OAR) and TVs was previously unknown.

Purpose of the Study:

• To compare dosimetric parameters between breast cancer treatment plans based on clinical landmarks versus RTOG-defined target volumes.
• To evaluate the effect of RTOG guidelines on target volume coverage and OAR dose distribution.

Main Methods:

• Retrospective analysis of 14 patients treated with clinical landmark-based plans (Group I) and 14 with target volume-based plans (Group II).
• All plans delivered a median dose of 50.4 Gy to the breast/chest wall, axilla (Ax), supraclavicular (SCV), and internal mammary lymph nodes (IMN).
• Dose-volume histograms (DVH) were computed for TVs and OARs, and DVH parameters were compared between groups.

Main Results:

• Target volume coverage improved for the SCV (V90: 78.0% vs. 93.6%, p=0.02) and intact breast (V95: 95.6% vs. 99.3%, p=0.007) in Group II.
• Dose to the spinal cord, lung (V20Gy, V30Gy), and contralateral breast (V5Gy) remained unchanged between groups.
• Low dose to the heart (V5Gy, V10Gy) and ipsilateral lung (V5Gy) significantly decreased in Group II (p<0.05 for all).

Conclusions:

• Treatment planning using RTOG consensus guidelines improves coverage of specific target volumes in breast cancer radiotherapy.
• Utilizing RTOG target volumes does not elevate radiation dose to critical OARs such as the contralateral breast, spinal cord, heart, or lungs.
• Further follow-up is necessary to correlate these dosimetric improvements with clinical outcomes.