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Evaluation of Organs at Risk (OAR) Sparing in Left Breast Irradiation Techniques

A Saini

A Saini1*, I Das2 , C hwang3 , M Biagioli4 , (1) ,Oviedo, FL, (2) NYU Langone Medical Center, New York, NY, (3) Florida Hospital Cancer Institute, Altamonte Springs, Florida, (4) Florida Hospital Cancer Institute, Orlando, FL


SU-I-GPD-T-407 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To compare dose to organs at risk (OAR) for left sided breast radiation therapy with comparable planning target volume (PTV) coverage in 4 techniques; free breathing in supine position (FB), deep inspirational breath holds in supine (sDIBH), free breathing in prone position (PP) and deep inspirational breath hold in prone position (pDIBH).

Methods: Ten left sided breast cancer patients suitable for hypofractionated treatment (42.56 Gy; 2.66 Gy/fr in 16 fractions) underwent a CT scan in four techniques e.g. FB, sDIBH, PP, pDIBH. One radiation oncologist contoured the PTV and OAR (cardiac components) based on RTOG guidelines. Treatment plans were optimized using field-in-field technique with AAA algorithm. Each plan was optimized to provide identical coverage to PTV such that a reasonable comparison in OAR dosimetry can be evaluated.

Results: Average lung Dmean, V10, V20 and V30 for PP (0.89 Gy, 1.22%, 0.56%, and 0.3% ) and pDIBH (0.86 Gy, 1.11%, 0.67% and 0.43%) is significantly lower than FB (4.83 Gy, 11.63%, 8.52%, and 6.43%) and sDIBH (4.54 Gy, 10.58%, 7.66%, 5.91%). Similarly, average heart Dmean, V2.5, V5, V10, and V20 were much lower in PP (1.0 Gy, 7.23%, 1.46%, 0.4%, and 0.15%), pDIBH (0.81 Gy, 4.56%,0.6%,0.1%, 0.09%) and in sDIBH (1.01 Gy, 6.17%, 1.4%, 0.65%, and 0.4%) compared to FB (1.58Gy, 11.64%, 3.5%, 1.94% and 1.21%) respectively. Similar findings were also noted in the heart components i.e LAD and LV correlated to radiation related toxicity.

Conclusion: Based on the calculated dose FB technique provides highest heart and lung dose. Prone technique has lowest lung dose, and pDIBH has lowest LAD dose. It is found that PP and pDIBH is always superior for heart, LV, LAD and lung as compared to FB. This conclusion is in contrast to some published study concluding that prone position has no benefit for heart sparing.

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