Simon Lo - Controversies in Radiation Oncology

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Radiation therapy plays an integral role in the multidisciplinary management of breast cancer. In appropriately selected patients, radiotherapy substantially decreases the risk of recurrence and results in improved survival. Within the previous two decades, considerable progress has been made toward selecting patients most likely to benefit from radiation, along with technical improvements that minimize the burden and toxicity associated with treatment while maximizing clinical benefit.

In an effort to clarify the rationale for increasingly complex clinical decisions, this chapter reviews the rich literature from practice-changing clinical trials in recent years, with an emphasis on the indications for radiation in the context of evolving surgical and systemic treatments, optimal approaches that maximize the therapeutic ratio, and appropriate treatment targets, both after breast-conserving surgery and mastectomy.

Several randomized trials have demonstrated equivalent survival after mastectomy as compared to breast-conserving surgery with radiation in appropriately selected patients, allowing women to choose a more limited surgical procedure without compromising disease control (Fisher et al. ) and is included as a measure of treatment quality (Surgeons ACo Commission on Cancer Quality of Care Measures; National Quality Measures for Breast Centers).

More recently, the improvement in locoregional control with radiotherapy has been associated with reduction in the overall risk of a recurrence and modest survival benefit as well. The Early Breast Cancer Trialists Collaborative Group (EBCTCG) meta-analysis of data from 10,801 individual patients in 17 studies demonstrated that radiation reduced the 10-year risk of any recurrence from 35 to 19.3 % and reduced the 15-year risk of death from breast cancer from 25.2 to 21.4 % (Clarke et al. ).

However, while the relative benefits of radiation are similar for all patients, the absolute benefit obtained from radiotherapy varies considerably according to patients baseline risk. The EBCTCG analyses have suggested that the survival benefit may be limited to those who obtain the largest absolute risk reduction from treatment, rather than those in whom the absolute benefit in recurrence risk reduction is less than 10 % (Darby et al. ).