Program Information
Predicting Mean Heart Dose in Left Sided Breast Cancer Patients
D Mathieu*, N Cote , S Bedwani , N Lahaie , A Bernard , J Aubry , D Roberge , S Lavertu , P Rousseau , T Vu , Centre hospitalier de l'Universite de Montreal (CHUM), Montreal, Quebec
Presentations
SU-I-GPD-J-72 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The aim of this study is to determine if free breathing (FB) treatment planning images can be used to identify left-sided breast cancer patients benefiting from deep inspiration breath hold (DIBH) irradiation.
Methods: Thirty two early-stage left-sided breast cancer patients who underwent breast-conserving surgery followed by adjuvant hypofractionated whole breast radiotherapy using tangential IMRT were included. Planning image acquisition included a FB and a DIBH CT scan. Patients received 42.5 Gy in 16 fractions by DIBH tangential irradiation. FB tangential IMRT plans were retrospectively optimized to obtain equivalent DIBH planning target volume coverage. Tangential field placement and organs at risk delineation were performed by a radiation oncologist as per RTOG 1005. Correlation between mean heart dose and in-field heart volume was obtained through linear analysis. A medical physicist placed breast tangential fields on FB images and estimated in-field heart volume from maximum depth of heart penetration assuming a spherical cap equation. Sensitivity and specificity in selecting patients with critical mean heart dose ≥3 Gy was performed using estimated in-field heart volume.
Results: Means (±SD) for delineated heart volume, in-field heart volume and mean heart dose were respectively 658 ± 97 cc, 25 ± 17 cc and 2.6 ± 1.0 Gy. A correlation between mean heart dose (D) and irradiated heart volume (V) was found through linear regression (D = 0.05 ⋅ V + 1.29; R2 = 0.84). Means for estimated depth of heart penetration and in-field heart volumes were respectively 1.4 ± 0.5 cm and 28 ± 18 cc. Sensitivity and specificity in identifying patients with mean heart dose ≥3 Gy from estimated in-field heart volumes were 90% and 100%.
Conclusion: Tangential field placement can be performed on FB treatment planning acquisition images for rapid selection of left-sided breast cancer patients who will most benefit from DIBH irradiation.
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