Is sentinel node biopsy necessary in conservatively treated DCIS?

We sought to identify the risk of axillary node involvement in patients with ductal carcinoma in situ (DCIS) and to determine whether axillary node assessment is necessary in these patients. Sentinel node biopsy (SNB) is replacing standard axillary lymph node dissection (ALND) for surgical staging of invasive breast cancer. Its use in patients with DCIS versus local excision (LE), observation, and/or breast irradiation remains in question. We examined the records of 813 patients with localized DCIS and disease-negative margins after LE who were randomly assigned to no further therapy or to breast irradiation in National Surgical Adjuvant Breast and Bowel Project (NSABP) trial B-17 and 1799 patients randomized to receive placebo or tamoxifen after LE + radiotherapy in NSABP trial B-24. An ALND was performed in 253 patients in NSABP B-17 and in 162 in NSABP B-24. We found that in NSABP trial B-17, seven patients developed ipsilateral nodal recurrence (INR). Overall INR rate was 0.83/1000 patient-years. In NSABP B-24, overall INR rate was 0.36/1000 patient-years. INR can be considered a surrogate for axillary involvement at the time of DCIS diagnosis. INR in patients with DCIS treated conservatively is extremely rare. Our findings do not support the routine use of SNB in patients with conservatively treated, localized DCIS.