Comparison of dose distributions with TG-43 and collapsed cone convolution algorithms applied to accelerated partial breast irradiation patient plans

Publication date: Available online 28 March 2016
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Sara L. Thrower, Simona F. Shaitelman, Elizabeth Bloom, Mohammad Salehpour, Kent Gifford
Purpose/ObjectiveBrachytherapy dose calculation algorithms that account for heterogeneous patient geometries have recently become commercially available. However, a retrospective comparison of the new collapsed cone convolution (CCC) with the current standard on a large cohort of patients treated with either a Strut-Adjusted Volume Implant (SAVI) or Contura® balloon device has not yet been completed. We compared the treatment plans for accelerated partial breast irradiation calculated by the new commercially available CCC and current standard TG-43-based algorithms for 50 patients treated at our institution with either a SAVI or Contura® device.Methods and MaterialsWe recalculated target coverage, volume of highly dosed normal tissue, and dose to organs at risk (ribs, skin, and lung) with each algorithm. For one case, an artificial air pocket was added to simulate 10% nonconformance. We performed a Wilcoxon signed rank test to determine the median differences in the clinical indices V90, V95, V100, V150, V200, and highest-dosed 0.1 cc and 1.0 cc of rib, skin, and lung between the two algorithms.ResultsThe CCC algorithm calculated lower values on average for all dose-volume histogram parameters. Across the entire patient cohort, the median difference in the clinical indices calculated by the two algorithms was < 10% for dose to organs at risk, < 5% for target volume coverage (V90, V95, and V100), and < 4 cc for dose to normal breast tissue (V150 and V200). No discernable difference was seen in the non conformance case.ConclusionsWe found that on average over our patient population CCC calculated (<10%) lower doses than TG-43. These results should inform clinicians as they prepare for the transition to heterogeneous dose calculation algorithms and determine if clinical tolerance limits warrant modification.

Teaser

We conducted a retrospective analysis of 50 brachytherapy accelerated partial breast irradiation patient plans comparing the dose distributions calculated by TG-43 and the collapsed cone convolution (CCC) algorithms. We found that the planning target volume coverage (V90, V95, and V100) differed < 5%, dose to organs at risk differed < 10%, and volume of highly-dosed normal tissue (V150,V200) differed < 4cc between algorithms. On average, the CCC algorithm calculated lower doses than the TG-43 algorithm.


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