Statement: Candidates for the primary trial are expected to be capable of holding their breath for half a minute.
Primary_evidence: Inclusion Criteria:   Women with diagnosis of breast malignancy   Women whom requires left chest wall post-mastectomy radiation with or without bolus   Age  18 years.   Performance status ECOG </=3   Women of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry, for the duration of study participation, and for 90 days following completion of therapy. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately Ability to understand and the willingness to sign a written informed consent.   Patient must be able to maintain a 30 second breath hold.   Conventional chest wall radiation delivery dose of 50.4 Gy/ 28 fractions with or without a boost (boost will not be evaluated for endpoints) Exclusion Criteria:   Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.   Subjects must not be pregnant or nursing due to the potential for congenital abnormalities and the potential of this regimen to harm nursing infants.