Encrypted login | home

Program Information

Three-Field Conformal Radiation Therapy for Palliation of Vertebral Metastasis: Beyond Parallel-Opposed Fields

J Zhang

J Zhang1,2*, L Lawrenson1,2 , J Moayyad1,2 , J Cho-Lim1,2 , S Lee1,3,4 , W Inouye1,2 , (1) VA Long Beach Healthcare System,Long Beach, CA, (2) Department of Radiation Oncology, University of California, Irvine, Orange, CA, (3) VA Greater Los Angeles Healthcare System, Los Angeles, CA, (4) David Geffen School of Medicine, university of California, Los Angeles


SU-I-GPD-T-372 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Despite advances in radiotherapy technology including 3-dimensional conformal radiation therapy (CRT), parallel-opposed AP/PA field arrangement remains the predominant approach for palliation of most vertebral metastases below the neck. To further minimize toxicity, we provide dosimetric assessments for at-risk normal tissue organs by comparing 3-field (AP or PA, plus a pair of symmetrically oblique beams) plans versus the traditional AP/PA CRT techniques.

Methods: Dosimetric data are analyzed from dose-volume histograms for paired comparisons between 3-field and AP/PA CRT plans for skeletal metastatic sites spanning from lower cervical to sacral spine (n=37). All target volumes were prescribed to receive 30 Gy in 10 fractions at a 90% isodose line that encompasses the entire vertebral body. Data are reported as mean ± standard deviation (x ± SD) and considered different where paired t-test results in p<=0.05*.

Results: High-dose volumes (V90% - volume receiving 90% or more of the prescribed dose) were reduced by half in the 3-field vs. the AP/PA plans, (1109±469 vs. 2262±869 cc). Slightly higher lung and kidney doses were delivered by the 3-field vs. the AP/PA plans, (lung: 7.0±5.5 vs. 4.0±3.1 Gy*, n=13; kidney: 9.6±6.1 vs. 2.2±2.7 Gy*, n=24). Both volume and dose were significantly reduced for midline organs in the 3-field vs. the AP/PA plans (bowel: V100% of 7±15 vs. 450±280 cc*, n=27; heart: 9.6±4.4 vs. 13.0±7.0 Gy*, n=10).

Conclusion: The use of 3-field CRT to treat vertebral metastases can significantly reduce doses to midline organs (heart and bowel), at the cost of slightly increased doses to kidneys and lungs. Therefore, it may offer a superior alternative to the traditional AP/PA-based CRT, particularly when toxicity to midline structures is of concern. These data are novel and clinically relevant in many cases, as 3-field CRT may also allow for hypofractionation, dose escalation, or re-treatment in the palliative setting.

Contact Email: