Dosimetric Evaluation of a Flexible Dual Balloon-Constructed Applicator in Treating Anorectal Cancer

Hsiang-Chi Kuo; Keyur J Mehta; Ravindra Yaparpalvi; Alan Lee; Dinesh Mynampati; William Bodner; Madhur Garg; David Huang; Wolfgang A Tomé; Shalom Kalnicki

doi:10.1177/1533034617707433

Dosimetric Evaluation of a Flexible Dual Balloon-Constructed Applicator in Treating Anorectal Cancer

Technol Cancer Res Treat. 2017 Dec;16(6):879-884. doi: 10.1177/1533034617707433. Epub 2017 May 8.

Authors

Hsiang-Chi Kuo^{1

2}, Keyur J Mehta^{1

2}, Ravindra Yaparpalvi^{1

2}, Alan Lee¹, Dinesh Mynampati¹, William Bodner^{1

2}, Madhur Garg^{1

2}, David Huang³, Wolfgang A Tomé^{1

2}, Shalom Kalnicki^{1

2}

Affiliations

¹ Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY, USA.
² Albert Einstein College of Medicine, Bronx, NY, USA.
³ Medical Physics Graduate Program, Duke Kunshan University, Shan-Hai, China.

Abstract

Background and purpose: To assess the dosimetric flexibility of a dual balloon brachytherapy applicator developed for the treatment of anorectal lesions.

Materials and methods: Different amounts of water were infused into the inner and outer balloon separately to study the asymmetrical distribution of the catheter, the radial distance of the active source channel to the inner surface of the global target volume , the space between the active source channels, and their dosimetric impact to target tissues and uninvolved rectum.

Results: Increasing inner balloon volume directly increased both the space between the active source channels and the radial distance of the active source channel to the inner surface of the global target volume. The space between the active source channels and the percentage of global target volume received 150% or more of the prescribed dose to target had a strong inverse correlation (-0.881/P = .007, -0.976/P = .001, respectively) with the radial distance of the active source channel to the inner surface of the global target volume. Conformity index, dose to 2 cm³ of rectum, and total reference air kerma were strongly correlated with the radial distance of the active source channel to the inner surface of the global target volume, with values of 0.952 (P = .001), 0.833 (P = .015), and 0.922 (P = .002), respectively. Percentage of global target volume received 150% or more of the prescribed dose was significantly correlated with the space between the active source channels (0.81/P = .022), and conformity index was strongly inversely correlated with the space between the active source channels (-0.833/P = .015).

Conclusion: The dual balloon-constructed Anorectal Applicator offers a flexible way to adjust the distances of the active source positions to the target in relation to uninvolved rectal wall. This flexibility simplifies planning which results in a highly conformal dose distribution to the target lesion while minimizing dose to normal rectal tissue.

Keywords: brachytherapy; dual balloon; rectal cancer.