PT  - JOURNAL ARTICLE
AU  - Kazda, Tomas
AU  - Vrzal, Miroslav
AU  - Prochazka, Tomas
AU  - Dvoracek, Petr
AU  - Burkon, Petr
AU  - Pospisil, Petr
AU  - Dziacky, Adam
AU  - Nikl, Tomas
AU  - Jancalek, Radim
AU  - Slampa, Pavel
AU  - Lakomy, Radek
TI  - Left hippocampus sparing whole brain radiotherapy (WBRT): A planning study
DP  - 2017 Dec 24
TA  - Biomedical papers
PG  - 397--402
VI  - 161
IP  - 4
AID - 10.5507/bp.2017.031
IS  - 12138118
AB  - Aims: Unilateral sparing of the dominant (left) hippocampus during whole brain radiotherapy (WBRT) could mitigate cognitive decline, especially verbal memory, similar to the widely investigated bilateral hippocampus avoidance (HA-WBRT). The aim of this planning study is dosimetrical comparison of HA-WBRT with only left hippocampus sparing (LHA-WBRT) plans.
Methods: HA-WBRT plans for 10 patients were prepared in accordance with RTOG 0933 trial and served as baseline for comparisons with several LHA-WBRT plans prepared with an effort: 1) to maintain the same left hippocampus dosimetry ("BEST PTV") and 2) to maintain same dosimetry in planning target volume as in HA-WBRT ("BEST LH").
Results: All HA-WBRT plans met RTOG 0933 protocol criteria with a mean Conformity index 1.09 and mean Homogeneity index (HI) 0.21. Mean right and left hippocampal D100% was 7.8 Gy and 8.5 Gy and mean Dmax 14.0 Gy and 13.8 Gy, respectively. "BEST PTV" plans reduced HI by 31.2% (P=0.005) which is mirrored by lower PTV_D2% (-0.8 Gy, P=0.005) and higher PTV_D98% (+1.3 Gy, P=0.005) as well as decreased optic pathway's Dmax by 1 Gy. In "BEST LH", mean D100% and Dmax for the left hippocampus were significantly reduced by 11.2% (P=0.005) and 10.9% (P=0.005) respectively.
Conclusions: LHA-WBRT could improve target coverage and/or further decrease in dose to spared hippocampus. Future clinical trials must confirm whether statistically significant reduction in left hippocampal dose is also clinically significant.