Breast-conserving surgery alone without radiation therapy has been compared with breast-conserving surgery followed by radiation therapy in six prospective randomized trials (including the National Surgical Adjuvant Breast and Bowel Project's trial [NSABP-B-06] and the Cancer and Leukemia Group B's trial [CLB-9343]).[6,33,34,35,36,37] In two of these trials, all patients also received adjuvant tamoxifen.[36,37] Every trial demonstrated a lower in-breast recurrence rate with radiation therapy, and this effect was present in all patient subgroups. In some groups, for example, women with receptor-positive small tumors  and those older than 70 years, the absolute reduction in the rate of recurrence was small (<5%). The limited impact of radiation therapy in this group of women was also reported in a confirmatory observational study looking at in-breast control rates using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. The impact of radiation therapy on local control was additionally clarified by showing that healthy women aged 70 to 79 years were most likely to benefit from radiation therapy (number needed to treat [NNT] to prevent one event = 21–22 patients) when compared to women aged 80 years or older or to those who have comorbidities (NNT = 61–125 patients). The administration of radiation therapy may be associated with short-term morbidity, inconvenience, and potential long-term complications.
Axillary lymph node surgery
The axillary lymph nodes should be staged to aid in determining prognosis and therapy. Sentinel lymph node (SLN) biopsy is the initial standard axillary staging procedure performed in women with invasive breast cancer. The SLN is defined as any node that receives drainage directly from the primary tumor, therefore, allowing for more than one SLN, which is often the case. Studies have shown that the injection of technetium-labeled sulfur colloid, vital blue dye, or both around the tumor or biopsy cavity, or in the subareolar area, and subsequent drainage of these compounds to the axilla results in the identification of the SLN in 92% to 98% of patients.[40,41] These reports demonstrate a 97.5% to 100% concordance between SLN biopsy and complete axillary lymph node dissection (ALND).[42,43,44,45]