Comparison of Axxent-Xoft, 192Ir and 60Co high-dose-rate brachytherapy sources for image-guided brachytherapy treatment planning for cervical cancer

Objective: To evaluate the dosimetric differences and similarities between treatment plans generated with Axxent-Xoft electronic brachytherapy source (Xoft-EBS), Ir-192 and Co-60 for tandem and ovoids (T&O) applicators. Methods: In this retrospective study, we replanned 10 patients previously treated with 192Ir high-dose-rate brachytherapy. Prescription was 7G x 34 fractions to Point A. For each original plan, we created two additional plans with Xoft-EBS and Co-60. The dose to each organ at risk (OAR) was evaluated in terms of V-35% and V-50%, the percentage volume receiving 35% and 50% of the prescription dose, respectively, and D-2cc, highest dose to a 2cm(3) volume of an OAR. Results: There was no difference between plans generated by Ir-192 and Co-60, but the plans generated using Xoft-EBS showed a reduction of up to 50% in V-35%, V-50% and D-2cc. The volumes of the 200% and 150% isodose lines, however, were 74% and 34% greater than the comparable volumes generated with the Ir-192 source. Point B dose was on average only 16% of the Point A dose for plans generated with Xoft-EBS compared with 30% for plans generated with Ir-192 or Co-60. Conclusion: The Xoft-EBS can potentially replace either Ir-192 or Co-60 in T&O treatments. Xoft-EBS offers either better sparing of the OARs compared with Ir-192 or Co-60 or at least similar sparing. Xoft-EBS-generated plans had higher doses within the target volume than Ir-192-or Co-60-generated ones. Advances in knowledge: This work presents newer knowledge in dosimetric comparison between Xoft-EBS, Ir-192 or Co-60 sources for T&O implants.