Prospective Assessment of Deep Inspiration Breath Hold to Prevent Radiation Associated Cardiac Perfusion Defects in Patients With Left-Sided Breast Cancer

PTV was modified accordingly. Cosmesis was scored according to the Harvard scale at the 3 month follow up visit. Results: Since February 2014, ten patients were enrolled on this prospective registry. Median age was 57.4 (range: 42 e 77). Mean PTV volume was 76.4 cc (range: 131 e 54.6 cc), representing a 64% reduction in volume when compared to a conventional PTV margin. Mean time in treatment room was 36 min, of which 15 min was spent on patient set up and MR imaging. 100 online volumetric MR images were available for evaluation. The mean 90% and 95% prescription dose covered 99.7% (range: 99.1-100%) and 97.6% (range: 90.5 e 99.9%) of PTV respectively. Mean inter-fraction standard deviation in 90% and 95% prescription coverage was less than 1% of PTV (90% prescription coverage: 0.26% PTV, and 95% prescription coverage: 0.63% PTV). Evaluation of cine MR during treatment did not demonstrate significant intra-fractional motion. Maximum skin dose was less than prescription in all cases. Nine of the ten patients had 3 month cosmetic data collected per the Harvard scale for breast cosmesis. All nine patients had excellent (7/9) or good (2/9) cosmetic results. Conclusion: Delivery of MR-guided APBI with reduced margins achieved appropriate target coverage based on assessment of actual delivered dose with favorable short term cosmesis. To our knowledge, this is the first series of APBI patients to be treated using MR-IGRT with minimal margins, thereby sparing a greater proportion of normal breast. Efforts to collect local control and long term cosmetic data are currently underway. Author Disclosure: S. Acharya: None. B.W. Fischer-Valuck: None.M.C. Roach: None. R. Kashani: None. L.L. Ochoa: None. M. Yang: None. S. Mutic: Honoraria; Philips Healthcare. Consultant; ViewRay. Travel Expenses; American Association of Medical Dosimetrists, American Association of Physicists in Medicine, American Society for Therapeutic Radiation Oncology. Stock; TreatSafely, Radialogica. I. Zoberi: None. M.A. Thomas: None.