P3-07-24: Accuracy and Cost Effectiveness of Frozen Section Examination of the Sentinel Lymph Node (SLN) in Ductal Carcinoma In Situ (DCIS) of Breast.

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Abstract Background: SLN biopsy (SLNB) can avoid reoperation for axillary staging in DCIS patients upstaged to invasive breast cancer (IBC) following resection. Intraoperative frozen section (IFS) examination of the SLN is a widely accepted tool for IBC patients in order to select candidates for axillary lymph node dissection (ALND), and avoid reoperation. Until now, utility of IFS in DCIS patients has not been addressed. Methods: Data from DCIS patients undergoing resection with SLNB (2000-11) was analyzed to determine the utility and cost of IFS exam and its impact on axillary management. A binomial regression analysis was performed to assess factors predictive of IFS positivity and SLN metastases (SLNM). Results: 401 patients (core biopsy, N=276, or excisional biopsy, N=125) underwent partial (N=84) or total mastectomy (N=317) with SLNB. 77 patients (19.2%) were upstaged to IBC. SLNM were identified in 24 patients (5.9%). Immunohistochemistry (IHC) positive individual tumor cells (ITCs) was the most common pattern of SLNM (N=12, 50%), SLN micrometastasis (SLNmi) was identified in 9 patients (37.5%) and macrometastases in 3 patients (12.5%). IFS exam was positive in only 5 patients (1.2%) with a sensitivity and specificity of 20.8% and 100%. IFS was negative in 396 patients (98.7%) yielding a false negative rate (FNR) of 79.2%. IFS costs $300,480 in DCIS patients of which only $2,970 was applicable to IFS positive patients (N=5). 11 of 24 patients with SLNM underwent ALND, revealing only 1 patient with further metastasis. Presence of IBC or DCIS with micro-invasion, multi-focal/multi-centricity, and advanced tumor stage were associated with SLNM (p<0.05), however no clinico-pathologic variables were predictive of IFS positivity. Conclusions: Most common patterns of SLNM in DCIS (ITCs/SLNmi) were identified only on routine pathologic assessment. Utility of IFS examination in DCIS patients is limited by poor sensitivity, high FNR and increased costs. Higher axillary nodal metastases are rare and prognostic significance of SLNmi/ITCs in DCIS is unproven. IFS examination of SLN in DCIS can be safely omitted and ALND should be performed only for SLN macrometastases. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-24.