Abstract P2-01-03: What to do with non-visualized sentinel nodes; to dissect or not to dissect the axilla?

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Abstract Background Both in the literature and in international guidelines evidence is scarce on clinicopathological characteristics and axillary treatment recommendations in patients with a non-visualized sentinel node (nvSN) during the sentinel lymph node (SLN) procedure. Therefore, this study aims to evaluate the prevalence of nvSN in a Dutch population of breast cancer patients and to compare their characteristics and prognosis with patients in whom the SLN could be visualized. Moreover, we have distributed a questionnaire among certified oncological surgeons in the Netherlands in order to determine their routine regarding the axillary treatment after a nvSN. Methods A retrospective population based study was performed including patients diagnosed with invasive breast cancer in the Netherlands between January 2000 and December 2013. Patients were included if they had no clinically palpable lymphadenopathy (cN0) or clinically apparent metastases (cM0). Patients receiving neo-adjuvant systemic treatment, patients with palpable axillary nodes and patients who did not undergo a SLN procedure were excluded. Also, a questionnaire containing 10 questions regarding clinical routine during the sentinel node procedure and axillary treatment of nvSN patients was distributed among 150 oncological (breast) surgeons. Results Of the 101,289 patients who fulfilled the inclusion criteria, 2545 (2.5%) had a nvSN. Univariate and multivariate analyses show that patients with a nvSN were older (p<0.001), were more often diagnosed in the years 2000-2005 (p<0.001), had a larger tumor (p=0.003) with more often a mastectomy (p=0.02) and were more likely to have ≥3 positive lymph nodes (p<0.001) compared to patients in whom the SLN could be visualized. However, adjusted survival analyses showed a borderline not-significant survival difference between these groups (HR=1.23, 95%CI=0.99-1.28). Of the 2545 patients with a nvSN, 2127 (84%) patients underwent an axillary lymph node dissection (ALND). Multivariate analyses show that patients receiving an ALND were more often diagnosed in the years 2000-2005, had a larger tumor and more often received adjuvant systemic therapy with both hormonal and chemotherapy. Adjusted survival analyses showed no statistically significant association between ALND and survival (HR=0.89, 95%CI=0.92-1.27). The questionnaire was completed by 122 (24%) oncological (breast) surgeons. It showed that 39% of the respondents estimated the prevalence of a nvSN to be 1-2%. Most surgeons are currently more reserved to perform an ALND than before the Z0011 trial, depending on various clinicopathological characteristics; 23 respondents answered to opt for an alternative axillary treatment option. Conclusion NvSN patients had worse disease characteristics compared to patients in whom the sentinel node could be visualized, though an ALND was not associated with a better survival. The results of the questionnaire show that surgeons are more reluctant to perform an ALND in case of a nvSN, especially after publication of the Z0011 trial, and that they would like the guideline to be revised and clarified regarding the axillary treatment in case of a nvSN. Citation Format: Verheuvel NC, Voogd AC, Tjan-Heijnen VCG, Roumen RMH. What to do with non-visualized sentinel nodes; to dissect or not to dissect the axilla? [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-01-03.