Radiation therapy after mastectomy for invasive breast cancer
This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.
Introduction: Radiation therapy isn’t often used after mastectomy for women with early stage breast cancer. However, it’s recommended for women with 4 or more positive lymph nodes to improve overall survival .
Radiation therapy after mastectomy is also strongly considered for women with 1-3 positive lymph nodes and for those who have positive tumor margins (when surgery to get negative tumor margins cannot be done) . A meta-analysis that combined the results of 22 randomized clinical trials found it lowered the risk of breast cancer recurrence and the risk of dying from breast cancer .
Radiation therapy after mastectomy should also be considered for women with negative lymph nodes who have :
- A tumor larger than 5 centimeters
- A tumor 5 centimeters or smaller, but the tumor margins are close
Learn more about radiation therapy.
Learn about the strengths and weaknesses of different types of studies.
Study selection criteria: Randomized clinical trials with at least 1,000 participants and 10 or more years of follow-up and meta-analyses.
Stage of Breast Cancer*
Number of Positive Nodes
Radiation Therapy after
No Radiation Therapy after
Randomized clinical trials
DBCG 82b Trial 
1,708 premenopausal women
4 or more
DBCG 82c Trial 
1,375 postmenopausal women
4 or more
1 or more
4 or more
Gebski et al. 
1 or more
SIG = Statistically significant difference between groups
NS = No statistically significant difference between groups
† Only included studies that used optimal radiation dose and coverage
‡ Calculated from data in study
- National Comprehensive Cancer Network. NCCN Clinical practice guidelines in oncology: Breast cancer, Version 6.2020. http://www.nccn.org, 2020.
- Early Breast Cancer Trialists’ Collaborative Group. Favourable and unfavourable effects on long-term survival of radiotherapy for early breast cancer: an overview of the randomised trials. Lancet. 355:1757-70, 2000.
- Overgaard M, Hansen PS, Overgaard J, et al. Postoperative radiotherapy in high-risk premenopausal women with breast cancer who receive adjuvant chemotherapy. Danish Breast Cancer Cooperative Group 82b Trial. N Engl J Med. 337:949-55, 1997.
- Overgaard M, Jensen MB, Overgaard J, et al. Postoperative radiotherapy in high-risk postmenopausal breast cancer patients given adjuvant tamoxifen: Danish Breast Cancer Cooperative Group DBCG 82c randomised trial. Lancet. 353:1641-8, 1999.
- Gebski V, Lagleva M, Keech A, et al. Survival effects of postmastectomy adjuvant radiation therapy using biologically equivalent doses: a clinical perspective. J Natl Cancer Inst. 98(1):26-38, 2006.