Thesis (Ph.D.) - Cairo University - Faculty of Medicine - Department of Oncology (Clinical)

Background: Conventional fractionated radiation therapy over 4-5 weeks with sequential boost used to be the only standard of care for postoperative RT treatment for patients with early stage breast cancer who undergo BCS for many years. However, the use of a modestly hypofractionated 15-16 fractions RT course has replaced the standard fractionated whole breast irradiation (SF-WBI) in many countries more than 10 years ago, which helped in reducing the waiting lists and machine loads as well as in improving patient compliance. With better understanding of the radiobiological rational of hypofractionated radiotherapy in tumors with low Ü/Ý ratio like the breast, further hypofractionation regimens were developed, and are showing non-inferior outcome in local control with acceptable cosmesis.Patients and Methods: This is a prospective phase II study conducted at Kasr El-Aini Center of Clinical Oncology and Nuclear Medicine (NEMROCK). Patients who underwent breast conservative surgery were recruited according to the inclusion and exclusion criteria. Recruited patients were planned using 3D conformal technique to receive a weekly hypofractionated radiation schedule using 28.5 Gy/5 fractions over 5 weeks with a fraction dose of 5.7 Gy to the whole breast. Dosimetric parameters for the coverage of the breast PTV were set using D95, D98 and the homogeneity index using the Dmax and the Dmin formula. Dose constrains for organ at risk (OAR), no more than 15% of the ipsilateral lung exceeds 8.55 Gy, no more than 5% of the whole heart exceeds 7.125 Gy and no more than 30% of the whole heart exceeds 1.425 Gy. All patients were evaluated for acute toxicity, cosmetic outcome and late toxicity

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