Post-mastectomy radiation therapy (PMRT) is indicated for tumors greater than 5 cm with any number of involved axillary nodes, smaller cancers with four or more lymph nodes involved with metastases, and locally advanced breast cancer by the American Society of Clinical Oncology (ASCO) and American Society of Therapeutic Radiology and Oncology (ASTRO).
The 12th St. Gallen International Breast Cancer Conference also supported the recommendation for post-mastectomy radiation therapy for patients with four or more axillary lymph nodes involved with cancer metastases.
Locally-advanced breast cancer is defined as a tumor greater than 5 cm in size, tumor extending to chest wall, and tumor extending to skin in the form of nodules, ulcerations, or edema. These patient populations have a risk of local recurrence greater than 20%, which is greatly improved with post-mastectomy radiation therapy.
Some groups recommend post-mastectomy irradiation for patients with T1 or T2 tumors and any number of positive axillary lymph nodes.
A recent meta-analysis performed by the Early Breast Cancer Trialists Collaborative Group showed that adjuvant radiotherapy significantly reduced the risk of local recurrence (from 23% to 6%) for patients with node-positive disease who underwent mastectomy with axillary clearance, which in turn reduced the rates of breast cancer mortality and overall mortality.
The most recent National Comprehensive Cancer Network Guidelines also strongly recommend post-mastectomy radiation therapy to the chest wall and regional lymph node basins for patients with any nodal positivity. However, this recommendation has been controversial for patients with one to three positive nodes, as many more recent studies using modern systemic therapy have shown much lower locoregional failure rates (5% to 10% at 5 to 10 years, or lower).
Many authors suggest that looking at the total number of risk factors in an individual patient would be useful to determine if post-mastectomy radiation therapy may be beneficial clinically. In addition to tumor size and the degree of nodal involvement, such factors include young age (35 to 40 years or less), lymphovascular invasion, high tumor grade, close or positive surgical margins, hormone receptor status, lymph node ratio, and lack of receipt of systemic therapy. The survival benefit is not uniform across all risk groups. The data in the literature on these variables are conflicting, however, and there is no consensus on how to integrate these factors.
Risk for and response to radiotherapy for local regional chest-wall recurrence are increasingly being linked to biologic subtype. The finding of micrometastases in a sentinel node would prompt discussion with a radiation oncologist about the benefits of post-mastectomy radiation therapy, but currently there is no randomized or prospective evidence to support definitive use of this modality in this population.
For all patient groups, when the risk of local-regional recurrence is less than 20%, patients should be offered a balanced discussion with a radiation oncologist so they can best understand their risks for recurrence based on their specific tumor features.
Dominici LS, Mittendorf EA, Wang X, et al. Implications of constructed biologic subtype and its relationship to locoregional recurrence following mastectomy. Breast Cancer Res. 2012;14:R82.
Early Breast Cancer Trialists Collaborative Group. Effect of radiotherapy after mastectomy and axillary surgery on 10-year recurrence and 20-year breast cancer mortality: meta-analysis of individual patient data for 8135 women in 22 randomized trials. Lancet. 2014;383:2127-2135.
Khan A, Haffty BG. Postmastectomy radiation therapy. In Kuerer H, ed. Breast Surgical Oncology. New York, NY: McGraw-Hill; 2010:995-1008.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology. Breast Cancer. Available at http://www.nccn.org.
Sharma R, Bedrosian I, Lucci A, et al. Present-day locoregional control in patients with t1 or t2 breast cancer with 0 and 1 to 3 positive lymph nodes after mastectomy without radiotherapy. Ann Surg Oncol. 2010;17:2899-2908.
Rodrigo Arrangoiz MS, MD, FACS, FSSO 