Physics Contribution
Whole Brain Radiotherapy With Hippocampal Avoidance and Simultaneously Integrated Brain Metastases Boost: A Planning Study

https://doi.org/10.1016/j.ijrobp.2007.05.038Get rights and content

Purpose

To evaluate the feasibility of using tomotherapy to deliver whole brain radiotherapy with hippocampal avoidance, hypothesized to reduce the risk of memory function decline, and simultaneously integrated boost to brain metastases to improve intracranial tumor control.

Methods and Materials

Ten patients treated with radiosurgery and whole brain radiotherapy underwent repeat planning using tomotherapy with the original computed tomography scans and magnetic resonance imaging–computed tomography fusion-defined target and normal structure contours. The individually contoured hippocampus was used as a dose-limiting structure (<6 Gy); the whole brain dose was prescribed at 32.25 Gy to 95% in 15 fractions, and the simultaneous boost doses to individual brain metastases were 63 Gy to lesions ≥2.0 cm in the maximal diameter and 70.8 Gy to lesions <2.0 cm. The plans were generated with a field width (FW) of 2.5 cm and, in 5 patients, with a FW of 1.0 cm. The plans were compared regarding conformation number, prescription isodose/target volume ratio, target coverage, homogeneity index, and mean normalized total dose.

Results

A 1.0-cm FW compared with a 2.5-cm FW significantly improved the dose distribution. The mean conformation number improved from 0.55 ± 0.16 to 0.60 ± 0.13. Whole brain homogeneity improved by 32% (p <0.001). The mean normalized total dose to the hippocampus was 5.9 ± 1.3 Gy2 and 5.8 ± 1.9 Gy2 for 2.5- and 1.0-cm FW, respectively. The mean treatment delivery time for the 2.5- and 1.0-cm FW plans was 10.2 ± 1.0 and 21.8 ± 1.8 min, respectively.

Conclusion

Composite tomotherapy plans achieved three objectives: homogeneous whole brain dose distribution equivalent to conventional whole brain radiotherapy; conformal hippocampal avoidance; and radiosurgically equivalent dose distributions to individual metastases.

Tomotherapy
Whole brain
Brain metastases
Conformal avoidance
Hippocampus

Cited by (0)

Supported by National Institutes of Health National Cancer Institute Grants 5 T32 GM08349, 5 RO1 CA109656, and P01 CA088960.

Conflict of interest: T. R. Mackie has a financial interest in TomoTherapy, Inc., and therefore has a potential conflict of interest.

View Abstract