The dosimetric impact of single, dual, and triple tandem applicators in the treatment of intact uterine cancer

Abstract Purpose To identify an optimal afterloading technique for high-dose-rate brachytherapy treatments in patients with medically inoperable uterine cancer. Methods and Materials Eighteen treatment plans were generated using point and volume-based techniques for three patients using a single, dual, and triple tandem. Dosimetric parameters of the target and critical structures were evaluated. Results Similar target coverage was achieved for each patient using volume-based planning; however, differences were evident when comparing point-based plans for the three applicators. In Patient 1, with a cylindrical uterus (8 cm by 4.5 cm), similar results were achieved with all three applicators ( V95 [Single] = 90.6%, V95 [Dual] = 90.6%, and V95 [Triple] = 91.5%). In Patient 2, who had a more spherical uterus (5 cm by 5.4 cm), the dual tandem was inferior to the others ( V95 = 65.9% vs. 83.7% with triple and 85.8% with single tandem). Analysis of isodose distributions showed that the dual tandem failed to achieve adequate coverage of the central portion of the fundus. In Patient 3, who had a uterus (6 cm by 5.5 cm) in close proximity to the bladder (0.5 cm) and bowel, both the triple and dual tandem point-based plans achieved better coverage than the single tandem, given dose constraints on the bladder and bowel, with uterus V95 of 83.4% (Triple), 84.9% (Dual), and 73.7% (Single), respectively. Conclusions For inoperable uterine cancer, optimal high-dose-rate applicator selection depends on the anatomy and location of the uterus and critical organs. The triple tandem applicator provides greater latitude in dose and anatomic uterus coverage as compared with either single or dual tandem applicators.