TITLE:
Stereotactic Radiotherapy Planning Using Modified Dynamic Conformal Arcs under Considering the Possibility for Amended Visual Organ Displacement Resulting from Early Tumor Shrinkage during Treatment for Perioptic Involvement of Myeloma
AUTHORS:
Kazuhiro Ohtakara, Hiroaki Hoshi
KEYWORDS:
Multiple Myeloma, Interfractional Anatomical Change, Dynamic Conformal Arcs, Image-Guided Radiotherapy, Stereotactic Radiotherapy
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.3 No.3,
August
27,
2014
ABSTRACT:
Treatment
planning of radiotherapy for skull base involvement of multiple myeloma
presenting with visual impairment should be optimized to alleviate symptoms
immediately and sufficiently while minimizing toxicities. Two such patients
were treated with fractionated stereotactic radiotherapy by using Dynamic Conformal Arcs (DCA)
under image guidance based on bony anatomy alignment. DCA planning was
optimized after considering the possibility for amendment of visual organ
displacement resulting from early tumor shrinkage during treatment through 1)
the use of a target volume with modified geometry as a surrogate for leaf
adaptation in order to improve target coverage, and 2) manual adjustment of a
subset of leaf positions to reduce the dose gradient immediately inside the
target boundary facing the visual organs and to eliminate an undesirable dose
hotspot. In both cases, anticipated geometric changes in the target volume
associated with improvement of visual organ displacement toward the target
centroid were observed before the completion of treatment. Favorable visual
functional outcomes as well as local tumor control were achieved during 14
months and 4 months follow-up periods. Notably, inexorable visual loss in one
patient was fully reversed within one month after radiotherapy. We described
the modification techniques for DCA planning in detail.