PURPOSE: To compare dosimetric endpoints between proton therapy (PT) and conventional radiation and determine the feasibility of PT for regional nodal irradiation (RNI) in @entity1 with @entity0 . METHODS AND MATERIALS: From 2012 to 2014, 18 @entity1 (stage IIA-IIIB) requiring RNI prospectively enrolled on a pilot study. Median age was 51.8  years (range, 42-73  years). The cohort included breast-conserving therapy (BCT) and mastectomy @entity1 and right- and left-sided @entity5 . Treatment targets and organs at risk were delineated on computed tomography scans, and PT and conventional plans were developed. @entity137 was prospectively recorded using Common Terminology Criteria for  Adverse Events version 4.0. A Wilcoxon signed-rank sum test compared the dose-volume parameters. The primary endpoint was a reduction in cardiac V5. RESULTS: Median follow-up was 20  months (range, 2-31  months). For all @entity1 , the PT plan better met the dosimetric goals and was used for treatment. Proton therapy alone was used for 10 @entity1 (9 postmastectomy, 1 after BCT) and combined proton-photon in 8 (6 BCT, 2 postmastectomy with immediate expander reconstruction). Proton therapy improved coverage of level 2 axilla (P=.0005). Adequate coverage of internal mammary nodes was consistently achieved with PT (median D95, 50.3  Gy; range, 46.6-52.1  Gy) but not with conventional radiation therapy (median D95, 48.2  Gy; range, 40.8-55  Gy; P=.0005). Median cardiac V5 was 0.6% with PT and 16.3% with conventional radiation (P<.0001). Median ipsilateral lung V5 and V20 were improved with PT (median V5 35.3% vs 60.5% [P<.0001]; and median V20, 21.6% vs 35.5% [P<.0001]). Grade 3 @entity1909 developed in 4 @entity1 (22%), which was the only grade 3 @entity137 . No grade 4+  @entity137 developed. CONCLUSION: Proton therapy for RNI after mastectomy or BCT significantly improves cardiac dose, especially for left-sided @entity1 , and lung V5 and V20 in all @entity1 without excessive acute @entity137 . Proton therapy simultaneously improves target coverage for the internal mammary nodes and level 2 axilla, which may positively impact long-term survival in @entity0 @entity1 .

Initial Report of a Prospective Dosimetric and Clinical Feasibility Trial Demonstrates the Potential of Protons to Increase the Therapeutic Ratio in XXXX Compared With Photons.

@entity1 :: ('9606', 'Species') :: ['women', 'patients'] @entity137 :: ('MESH:D064420', 'Disease') :: ['toxicity', 'Toxicity', 'toxicities'] @entity0 :: ('MESH:D001943', 'Disease') :: ['breast cancer'] @entity5 :: ('MESH:D009369', 'Disease') :: ['cancers'] @entity1909 :: ('MESH:D003872', 'Disease') :: ['dermatitis']
@entity0 :: (MESH:D001943,Disease) :: ['Breast Cancer']
