Radiobiologically optimized couch shift: A new localization paradigm using cone-beam CT for prostate radiotherapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Prostate Cancer Treatment

Background:

• External beam radiotherapy for prostate cancer requires precise patient positioning.
• Variations in patient setup can lead to suboptimal dose delivery and increased toxicity.
• Utilizing radiobiological principles can enhance treatment planning and delivery.

Purpose of the Study:

• To introduce a novel positioning strategy for prostate external beam radiotherapy.
• To optimize radiation delivery by incorporating radiobiological response knowledge.
• To evaluate the efficacy of this strategy in reducing toxicity.

Main Methods:

• Retrospective analysis of five prostate cancer patients undergoing VMAT.
• Generation of treatment plans and selection of pretreatment cone-beam CTs (CBCTs).
• Registration of CBCTs to planning CTs, followed by optimization to find the radiobiologically optimized couch shift position (ROCS-position) using dosimetric and radiobiological indices.

Main Results:

• The ROCS-position strategy maintained target dose coverage (EUDprostate, D99prostate) compared to observer-matched positions.
• It significantly reduced the Normal Tissue Complication Probability (NTCP) for the rectum.
• Patient 5 showed a reduction in rectal NTCP from 19.5% to 11.3% with ROCS-positioning.

Conclusions:

• Radiobiologically optimized positioning shows potential for improving online image-guided radiotherapy in prostate cancer.
• This approach can mitigate rectal toxicity while ensuring adequate tumor dose.
• Further investigation is warranted to validate these encouraging findings.