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It is indeed paradoxical that the use postmastectomy radiation therapy (PMRT) continues to cause considerable debate and controversy despite having been the subject of over 20 randomized prospective trials spanning 5 decades of research activity. In fact, some of the first prospective randomized trials ever conducted attempted to define the role of PMRT.1 Nonetheless, several important questions still await definitive answers.

Historically, PMRT was offered to the majority of women with breast cancer in the early and mid-20th century.2 Many of these women had locally advanced breast cancer, and oncologists of the time intuitively understood that additional locoregional therapy was needed for these women with a high burden of locoregional disease. Clinicians became cognizant of the potential risks of PMRT at the same time that surgical techniques improved and systemic therapy was developed. Consequently, the role of PMRT in the nascent therapeutic strategy for women with breast cancer came under rigorous scrutiny.

This chapter will focus exclusively on the topic of PMRT and is divided into 4 themes. First, the rationale for PMRT will be considered, by reviewing data supporting the efficacy of PMRT. Because the rationale for any intervention is contingent on the risks of the intervention, the risks and sequelae of PMRT will also be reviewed in this section. Second, data that attempt to shed light on the often vexing problem of appropriate patient selection will be reviewed. Third, breast reconstruction after mastectomy and its relevance to PMRT will be reviewed. Finally, the technique for PMRT will be discussed as well as the related issues of treatment volume and dose.

Efficacy of PMRT

The efficacy of irradiating the chest wall and draining lymph nodes after mastectomy in improving locoregional control has been firmly established by multiple older trials comparing mastectomy alone to mastectomy with postoperative radiation.3-9 These trials typically used outdated radiation techniques and equipment that produced orthovoltage x-rays. Orthovoltage x-rays produce suboptimal dose distributions that would never be used for therapy in the modern context. Because of these reasons, the relevance of these older trials is limited in the context of modern radiation therapy, but they adequately demonstrated 2 important facts: (1) PMRT can effectively reduce the burden of residual locoregional disease; and (2) in terms of treatment volume, radiation therapy is more comprehensive and more "radical" than even the most radical surgery. Notably, these trials did not demonstrate improvements in survival end points.

The locoregional effects of adjuvant systemic therapy alone (without radiation) can be studied through those trials of systemic therapy versus nil that have reported patterns of failure.10-24 In summary, data demonstrating an improvement in locoregional control with systemic cytotoxic chemotherapy are somewhat inconsistent. However, the most recent Early Breast Cancer Trialists Colloborative Group (EBCTCG) meta-analysis of systemic therapy trials reported statistically fewer isolated local relapses in patients receiving polychemotherapy (recurrence rate ratio of 0.63 and 0.70 for women < ...

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