ASO Author Reflections: The Role of Post-mastectomy Radiation Therapy in the Setting of Nodal Micrometastases

Excerpt

The recently revised SSO/ASTRO/ASCO guidelines recommend consideration of post-mastectomy radiation therapy (PMRT) in patients with nodal macrometastasis in one to three axillary nodes to reduce the risk of breast cancer death and local recurrence.1 The benefit associated with PMRT in patients with nodal micrometastases is not well-studied. This is in part because the randomized trials that showed the benefit of PMRT did not classify patients as having micrometastases due to the methods of lymph node detection at the time these studies were performed. Further complicating this question is the increasing omission of axillary lymph node dissection (ALND) in the setting of a positive sentinel lymph node biopsy (SLNB) based on randomized trials, which exclusively or primarily were comprised of lumpectomy patients.2,3 In these trials, the vast majority of patients had lumpectomy and therefore received at least whole breast irradiation, if not additional nodal fields.4 As such, these trials do not address the safety of omitting radiation entirely when patients undergo mastectomy with micrometastases found on SLNB. There have been single-institution trials addressing this question, which show low rates of locoregional recurrence (LRR) in patients with nodal micrometastases who did not undergo ALND or PMRT.5,6 However, it is possible that these studies lack the power to detect differences in LRR or overall survival (OS) due to the small numbers. …