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A brain tumor dose escalation protocol based on effective dose equivalence to prior experience
R K Ten Haken1, B A Fraass, A S Lichter
1Department of Radiation Oncology, The University of Michigan, Ann Arbor 48109-0010, USA.
International Journal of Radiation Oncology, Biology, Physics
|September 25, 1998
Summary
This study designed a new radiation therapy protocol for brain tumors, safely increasing the effective dose to the central tumor volume while maintaining efficacy and safety for surrounding tissues. The linear quadratic model was key to incorporating past treatment experience.
Area of Science:
- Radiation Oncology
- Medical Physics
- Neurosurgery
Background:
- Sequential dose escalation protocols for primary brain tumors have established safety profiles.
- Delivering higher effective doses to central target volumes is desirable for improved tumor control.
- Previous protocols provide valuable data for designing new treatment strategies.
Purpose of the Study:
- To design a novel conformal irradiation protocol for primary brain tumors.
- To preserve the safety and efficacy of a previous sequential dose escalation scheme.
- To enable delivery of substantially higher effective doses to a central target volume.
Main Methods:
- Utilized the linear quadratic model to normalize isoeffective composite dose distributions from 20 patients.
- Designed a new protocol to maintain efficacy and minimize toxicity in outer volumes while escalating dose to the inner planning target volume (PTV).
- Investigated treatment plans for feasibility, including simultaneous achievement of all biological objectives.
Main Results:
- New protocol maintains minimum doses of 60 Gy and 75 Gy to outer PTVs (PTV3 and PTV2).
- Achieved a higher dose of 90 Gy to the isocenter of the central PTV (PTV1) with required homogeneity.
- Treatment plans using noncoplanar beams and intensity modulation successfully treated all volumes daily.
Conclusions:
- Demonstrated the successful design of a new dose escalation protocol for brain tumors.
- Successfully incorporated past treatment experience using the linear quadratic model.
- The new protocol allows for higher effective doses to the central target volume.