Simultaneous integrated protection : A new concept for high-precision radiation therapy

Area of Science:

• Radiation oncology
• Medical physics

Background:

• Stereotactic radiotherapy requires careful planning near serial organs at risk (OAR).
• A novel intensity-modulated radiotherapy (IMRT) prescription concept, simultaneous integrated protection (SIP), is introduced for quantifiable dose prescription to targets adjacent to OARs.

Observation:

• SIP defines a protection volume (PTV_SIP) within the planning target volume (PTV) intersecting with the planning risk volume (PRV).
• Dose is prescribed to the dominant PTV (PTV_dom) and OAR constraints are managed using absolute and equieffective doses (EQD2).
• Planning iterations adjust fractionation if OAR constraints are violated, ensuring dose to PTV_SIP is maximized within safety limits.

Findings:

• SIP was applied in 6 patients with large airways or bowel as OARs across various fractionation schedules.
• Analysis of dose-volume histograms confirmed steep dose fall-off and adherence to OAR constraints (p=0.001).
• All patients achieved local control at a median 9-month follow-up with low toxicity.

Implications:

• SIP enables a median dose of ≥100% to the PTV, facilitating high local control and minimal toxicity.
• A prospective clinical trial is underway to further validate SIP in chest and abdomen stereotactic body radiotherapy.
• This approach offers a quantifiable and comparable method for dose prescription in complex radiotherapy cases.