Breast cancer is the leading cause of cancer in women worldwide, with over 2 million cases diagnosed every year. Although advances in treatment have led to an overall reduction in breast cancer mortality, survivors continue to have an ongoing risk of disease recurrence. For women who experience breast recurrence, mastectomy has historically been the only treatment approach offered. However, it has been associated with negative health outcomes, including reduced quality of life, depression and anxiety, and impaired sexual functioning. Fear of mastectomy has also been associated with delays in seeking appropriate and timely management of disease. As a result, there is increasing interest to identify treatment options that include breast preservation.~Breast-conserving surgery followed by re-irradiation with partial breast irradiation (rPBI) has recently been found to be a safe alternative to mastectomy for women who have undergone prior whole breast radiation. By reducing the volume of tissue receiving radiation, rPBI has been associated with less toxicity and improved cosmetic outcomes. However, previously published studies have used long fractionation regimens for rPBI delivered over 3 to 5 weeks, which can present a challenge for both patients and health systems. This is particularly true in low- and middle-income countries, where more than half of new breast cancer cases now occur.~For many women with early stage breast cancer, shorter 1-week (5-fraction) courses of breast radiation (ultra-fractionation) have been found to be equivalent to longer fractionation schedules in the upfront treatment setting. These 1-week schedules are more convenient for patients, with fewer treatments and shorter overall treatment time. The investigators hypothesize that they can accrue sufficient patient with rPBI who will be treated using 26Gy in 5 daily fractions over 1-week. Planned interim analysis after the 15 recruited patients for early toxicity evaluation with stopping rule for unacceptable toxicity.~Using an international network of comprehensive cancer centers, this study will advance global knowledge of how to optimally treat woman with this disease.
Breast-conserving surgery followed by re-irradiation with partial breast irradiation (rPBI) has recently been found to be a safe alternative to mastectomy for women who have undergone prior whole breast radiation. By reducing the volume of tissue receiving radiation, rPBI has been associated with less toxicity and improved cosmetic outcomes. For many women with early stage breast cancer, shorter 1-week (5-fraction) courses of breast radiation (ultra-fractionation) have been found to be equivalent to longer fractionation schedules in the upfront treatment setting. These 1-week schedules are more convenient for patients, with fewer treatments and shorter overall treatment time. The investigators hypothesize that they can accrue sufficient patient with rPBI who will be treated using 26 Gray(Gy) in 5 daily fractions over 1-week. Planned interim analysis after the 15 recruited patients for early toxicity evaluation with stopping rule for unacceptable toxicity.