A dosimetric comparison of Xoft Axxent Electronic Brachytherapy and iridium-192 high-dose-rate brachytherapy in the treatment of endometrial cancer

Purpose This analysis was undertaken to dosimetrically compare iridium-192 high-dose-rate brachytherapy (IB) and Xoft Axxent Electronic Brachytherapy (XB; Xoft Inc., Sunnyvale, CA) in the treatment of endometrial cancer. Methods and Materials The planning CT scans from 11 patients previously treated with IB were used to construct hypothetical treatment plans using the source characteristics of the XB device. The mean V95, V100, and V150 (percent of the planning target volume that received 95%, 100%, and 150% of the prescription dose) were calculated. For both the bladder and rectum, the V35 (percent of the organ that received 35% of the prescription dose) and V50 (percent of the organ that received 50% of the prescription dose) were calculated for each patient using both methods of vaginal brachytherapy. Results The mean %V95 was 99.7% vs. 99.6% (p = ns) and the mean %V100 was 99.0% vs. 99.1% (p = ns) for the IB and XB methods, respectively. The mean %V150 was 35.8% vs. 58.9% (p < 0.05) for the IB and XB methods, respectively. The mean bladder %V35 was 47.7% vs. 27.4% (p < 0.05) and the mean bladder %V50 was 26.5% vs. 15.9% (p < 0.05) for the IB and XB methods, respectively. The mean rectal %V35 was 48.3% vs. 28.3% (p < 0.05) and the mean rectal %V50 was 27.8% vs. 17.0% (p < 0.05) for the IB and XB methods, respectively. Conclusions The IB and XB methods of vaginal brachytherapy offer equivalent target volume coverage; however, the XB method allows increased sparing of the bladder and rectum.