Dose-mass inverse optimization for minimally moving thoracic lesions.

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Radiotherapy planning aims to escalate tumor dose while sparing healthy tissues.
• Dose-volume (DV) optimization is the current standard, but dose-mass (DM) optimization is emerging as a potential alternative.
• Evaluating DM optimization's efficacy in non-small cell lung cancer (NSCLC) is crucial.

Purpose of the Study:

• To compare the effectiveness of dose-mass (DM) optimization against dose-volume (DV) optimization for healthy tissue sparing in NSCLC patients.
• To quantify differences in organ at risk (OAR) sparing using both DV and DM planning approaches.

Main Methods:

• Retrospective analysis of 14 NSCLC patient plans, with tumor motion <0.5 cm and no motion management.
• Performed both DV-based and DM-based optimization using nine-field step-and-shoot intensity-modulated radiation therapy (IMRT).
• Compared standard dosimetric indices (DIs) and mass-based indices (MIs) for OARs (spinal cord, heart, esophagus) and healthy lung.

Main Results:

• DM optimization demonstrated superior OAR sparing, with average reductions of 23% for the spinal cord, 4% for the heart, and 6% for the esophagus.
• DM optimization generally resulted in lower lung doses and reduced volumes receiving high doses (e.g., 3-4% lower dose to 20-30% of lung).
• Statistical analyses confirmed significant OAR sparing with DM optimization, although sparing varied across different endpoints and cases.

Conclusions:

• Dose-mass optimization provides statistically significant organ at risk sparing compared to dose-volume optimization in NSCLC radiotherapy.
• While DM optimization shows promise, its benefits are case-dependent and not universally observed for all dosimetric endpoints.
• Further investigation into DM optimization's role in radiotherapy planning is warranted.