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. 2007 Oct 1;69(2):589-97.
doi: 10.1016/j.ijrobp.2007.05.038.

Whole brain radiotherapy with hippocampal avoidance and simultaneously integrated brain metastases boost: a planning study

Alonso N Gutiérrez  1 , David C Westerly, Wolfgang A Tomé, Hazim A Jaradat, Thomas R Mackie, Søren M Bentzen, Deepak Khuntia, Minesh P Mehta
Affiliations

Whole brain radiotherapy with hippocampal avoidance and simultaneously integrated brain metastases boost: a planning study

Alonso N Gutiérrez et al. Int J Radiat Oncol Biol Phys. .

Abstract

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 >or=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 Gy(2) and 5.8 +/- 1.9 Gy(2) 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.

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Conflict of interest statement

Conflict of Interest Notification:

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

Figures

Figure 1
Figure 1
Example segmentation of single brain metastasis (green) and hippocampus (blue) in a T1-weighted 3D-SPGR MR image data set of 1.25 mm slice thickness.
Figure 2
Figure 2
(Top) Example isodose distribution of WBRT-HA with SIB of three metastases using helical tomotherapy. (Bottom) Corresponding cumulative, normalized DVH for WBRT-HA with SIB to three metastases. Two metastases prescribed to 70.8 Gy (magenta & blue), one metastasis to 63 Gy (green), whole brain (red) to 32.25 Gy. Hippocampus (black) and eyes (cyan) are shown. Dashed line represents plan with 1.0cm FW, and solid line represents plan with 2.5cm FW—both pitch of 0.289. Plans normalized to prescription dose for comparison purposes.
Figure 3
Figure 3
(A) EDR2® film of coronal plane for sample patient treatment plan delivered in tomotherapy cylindrical solid water phantom. Profiles were acquired through metastasis (top yellow line) and hippocampus (bottom yellow line). Both profiles show superior correlation between measured and calculated dose distributions. (B) Gamma index distribution map between calculated and measured planar dose distributions shows good correlation.
See this image and copyright information in PMC

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