Evaluation of Heart Dose for Left-Sided Breast Cancer Patients Over an 11-Year Period Spanning the Transition From 2-Dimensional to 3-Dimensional Planning

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Abstract

Introduction/Background:

We evaluated heart dose from left breast radiotherapy with 2-dimensional (2D) versus 3-dimensional (3D) plans.

Patients and Methods:

Treatment plans from patients treated with standard fractionation for left breast cancer from 2003 to 2013 were reviewed, with patients grouped into 3 cohorts: 2003 to 2004 (“2D”, with computed tomography scans for dose calculation but fields defined using simulation films; n = 29), 2005 to 2006 (“2D-post,” after several influential articles on heart dose were published; n = 31), and 2007 to 2013 (“3D”; n = 256). All patients were treated with free-breathing technique. Heart volumes were retrospectively contoured for the earlier 2 cohorts. Mean heart dose (MHD) and percentage of structure receiving at least 25 Gy (V25 Gy) and percentage of structure receiving at least 5 Gy for the whole heart, left ventricle (LV), right ventricle (RV), and both ventricles were recorded and compared among cohorts.

Results:

MHD was 345 cGy (2D), 213 cGy (2D-post) and 213 cGy (3D). LV V25 Gy was 6.3%, 1.5%, and 1.1%, respectively. Lower doses were seen over time for all indices (analysis of variance, P < .0001). Post hoc tests indicated significantly higher doses for 2D versus 2D-post or 3D cohorts (P ≤ .001) for all parameters except RV V25 Gy (P = .24).

Conclusion:

Heart doses were higher with 2D versus 3D plans. Cardiac doses and resulting toxicity with modern 3D planning might be lower than those in previous reports.

Micro-Abstract:

In this study we examined the evolution in heart dose for patients treated with radiation for left-sided breast cancer from 2003 to 2013. Patients were grouped into 3 cohorts spanning the transition from 2-dimensional to 3-dimensional planning, and heart dose was calculated. Lower heart dose was seen over time, suggesting that modern treatment planning results in lower heart doses and, potentially, less toxicity.

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