Clinical significance of accounting for tissue heterogeneity in permanent breast seeds implant brachytherapy planning

Publication date: Available online 23 December 2015
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Shahram Mashouf, Emmanuelle Fleury, Priscilla Lai, Tomas Merino, Eli Lechtman, Alex Kiss, Claire McCann, Jean-Philippe Pignol
PurposeThe Inhomogeneity Correction Factor (ICF) method provides heterogeneity correction for the fast calculation TG43 formalism in seeds brachytherapy. This study compared ICF corrected plans to their standard TG43 counterparts looking at their capacity to assess inadequate coverage and/or risk of any skin toxicities for patients who received Permanent Breast Seed Implant (PBSI).Methods and MaterialsThe 2 month post implant CT-scans and plans of 140 PBSI patients were used to calculate dose distributions using the TG-43U1 formalism and the ICF method. Multiple dose-volume histogram (DVH) parameters of clinical target volume (CTV) and skin were extracted and compared for both ICF and TG43 dose distributions. Short term (desquamation and erythema) and long term (telangiectasia) skin toxicity data were available on 125 and 110 of the patients, respectively, at the time of study. The predictive value of each DVH parameter of skin was evaluated using the area under the receiver operating characteristic (ROC) curve for each toxicity endpoint.ResultsThe DVH parameters of CTV calculated using the ICF method showed an overall decrease compared to TG43 while those of skin showed an increase confirming previously reported findings on the impact of heterogeneity with low energy sources. The ICF methodology enabled us to distinguish patients for whom the CTV V100 and V90 are up to 19% lower compared to TG43, which could present a risk of recurrence not detected when heterogeneity are not accounted for. The ICF method also led to an increase in the prediction of desquamation, erythema, and telangiectasia91% of skin DVH parameters studied.ConclusionsThe ICF methodology has the advantage to distinguish any inadequate dose coverage of CTV due to breast heterogeneity, which can be missed by TG43. The use of the ICF correction also led to an increase in prediction accuracy of skin toxicities in majority of cases.

Teaser

In this study we compared a tissue heterogeneity correction algorithm (ICF method) to the standard AAPM-TG43 protocol for a cohort of patients treated with permanent breast seed implants (PBSI). Using heterogeneity correction enabled distinguishing patients who received lower dose to the clinical target volume (CTV), who would otherwise go undetected using TG43. The use of the ICF correction also led to an increase in prediction accuracy of skin toxicities in the majority of the cases.


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