Does the Presence of Cytokeratin Positive Individual Tumor Cells (N(0(I+))) in Sentinel Lymph Nodes Affect Clinical Outcomes in Breast Cancer Patients Treated with Accelerated Partial Breast Irradiation

PURPOSE: To report a primary objective clinical outcome of ipsilateral breast cancer recurrence following accelerated partial breast irradiation (APBI) with N(0(i+)) (single tumor cells or clusters <2mm) in sentinel lymph nodes. The secondary objective was to observe any incidence of ipsilateral breast failure. PATIENTS AND METHODS: Between March 2004 and April 2016, a total of 747 patients were enrolled in one of two APBI (Accelerated Partial Breast Irradiation) breast protocols (Phase II NCT01185145 and Phase III NCT01185132). Nineteen patients with N(0(i+)) disease were treated between February 2005 and December 2015. Patient eligibility included a primary invasive or DCIS tumor size <3 cm, N0(i+) disease, and margin width of >2 mm. All enrolled patients presented in this report had sentinel lymph node examinations. Clinical outcomes of ipsilateral breast, axillary and combined regional (breast or axillary) recurrences were analyzed. RESULTS: Median follow-up for all patients was 5 years (1–8 years). No patient experienced either ipsilateral breast or axillary recurrence. CONCLUSION: There has been scarce information/reporting of the treatment of patients with cytokeratin positive individual tumor cells N(0(i+)) with APBI. The authors have presented data which suggest that the successful outcomes of these patients might warrant further study.