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 . A meta-analysis that combined the results of 22 randomized clinical trials found it lowered the risk of recurrence and the risk of dying from breast cancer .
Radiation therapy after mastectomy should also be considered for women with negative lymph nodes who also have :
Learn more about radiation therapy.
Learn about the short-term side effects and long-term health risks of 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.
Study Population(number of participants)
Stage ofBreast Cancer*
Number ofPositive Nodes
Overall Survival(for length of follow-up)
Radiation Therapy afterMastectomy
No Radiation Therapy afterMastectomy
Randomized clinical trials
DBCG 82b Trial 
1,708 premenopausal women
4 or more
DBCG 82c Trial 
1,375 postmenopausal women
1 or more
Gebski et al. 
SIG = Statistically significant difference between groups
NS = No statistically significant difference between groups
* Breast cancer stage as classified before 2018
† Only included studies that used optimal radiation dose and coverage
‡ Calculated from data in study
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