A comparative analysis of 3DCRT, IMRT, and VMAT in the palliative treatment of spinal metastases.

Abstract

e20679 Background: Radiotherapy is very important in the palliation of spinal metastases. Traditionally, a simple two-dimensional single direct posterior spinal field giving unnecessary exit dose to the normal structures is used. The studies evaluating the recent advances like 3DCRT, IMRT, VMAT for spinal metastases are rare. Present study evaluates these three modalities for the treatment of spinal mets. Methods: Ten patients with metastases to the body of lumbar spine were included. Planning CT was done with the patient supine on Philips wide bore CT (for 3 mm). The CT images were transferred online to the Pinnacle TPS V.8.0M. Tumor and the critical structures like spinal cord, kidneys, liver and bowels were contoured on pinnacle. 3DCRT was planned on pinnacle with seven equidistant beams. The CT images with the contoured structures were sent to Monaco TPS V.3.10.02. IMRT (seven equidistant fields) and VMAT (a single 360 degree arc in 25 degree increments) were planned on Monaco. Dose: 30 Gy in 10 fractions. PTV indices analyzed: D mean, D2 (dose received by the hottest 2 percent volume), D98 (dose received by 98 percent), homogeneity index HI [(D2-D98)/D50)], and conformity index CI (PTV volume/volume of PTV covered by 95 percent isodose). Dmax and D2 (dose received by hottest 2cc) for the spine, V12, V18 and V28 (percent volume receiving the respective dose) for the kidneys, D50 (dose received by the 50 percent volume) of liver, V15 (percentage volume of bowel receiving 15 Gy) were evaluated. The average were calculated and compared. Statistical analysis was done by SPSS Version 14. Results: The Table shows that there is no much significant difference between the three plans for the PTV indices. But for the normal structures, VMAT provides the least dose followed by IMRT. Conclusions: VMAT is superior to IMRT and both are better than 3DCRT for normal tissue sparing in the palliative RT for spinal metastases. [Table: see text]