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IntroductionSentinel Lymphnode Biopsy (SLNB) is generally excepted as a minimal invasive technique to stage the axilla in clinically node negative breast cancer patients. Though the reported clinically overt axillary recurrences after negative SLNB is low (0-2,8%), these false negative results after SLNB remain a concern in the treatment of pN0(slnb) breast cancer patients. In this respect many have investigated factors that may influence the risk of developing an axillary recurrence, either to explain the unexpected low incidence or to try to identify subgroups of patients with higher risk of developing an axillary recurrence. Downside to many of these studies is the single-centre study design, mostly presenting small numbers of patients with relatively short follow-up making it difficult to extrapolate the results to the every-day practice.We conducted this multicentre cohort study to identify prognostic factors for developing axillary recurrences after negative SLNB.Patients and MethodsProspectively collected data from seven large volume hospitals in the Netherlands were analyzed. Patients underwent surgery including SLNB between January 2000 and December 2002. Pathological work-up of the sentinel node, local and systemic treatment, and follow-up were performed according to Dutch National guidelines. Statistical analysis was performed to test homogeneity between the institutes. Multivariate analysis was performed to identify prognostic factors. A p-value of 0,2mm) and underwent Axillary Lymphnode Dissection (ALND). In the remaining 1028 patients, 986 (61,7%) were SLN negative and 42 (2,6%) patients were found to have isolated tumor cells (i.e. metastases Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1006.

Introduction: Since the introduction of sentinel lymph node biopsy (SLNB) for staging breast cancer, lymphogenic micrometastases are commonly detected. The prognostic meaning of these small lymph node metastases and the consequences regarding the indication for adjuvant systemic treatment is under debate. Currently, robust data with a long time follow up are lacking.Method: Between January 2000 and December 2002 1411 patients with a cT1-2N0 breast carcinoma underwent surgery in seven hospitals in the Netherlands. Pathological examination of the sentinel node consisted of serial sectioning of SLN's and H&E and IHC staining. Based on the presence of lymph node metastases patients where divided into four groups: pN0 (n = 922), pN1micro (n = 103), pN1a (n = 285) and pN≥1b (n = 101). Median follow up was 77 months.Results: At the end of follow-up 184 (13.0%) patients had died. Breast cancer recurred in 244 (17.3%) patients, 165 of them having distant metastases (11.7%) patients. The 5- years overall survival was 93% for patients with pN0 disease, 94% for pN1micro, 88% for pN1a and 78% for pN≥1b (p < 0.001). The 5-years disease free survival was 87%, 90%, 85% and 72% (p < 0.001) respectively.Following adjustment for possible confounding characteristics and for adjuvant systemic treatment, overall survival was similar for pN0 en pN1micro patients and significantly worse for pN1a and pN≥1b (HR 1.18; 95% CI 0.58-2.39, HR 2.47; 95% CI 1.69-3.63, HR 4.36; 95% CI 2.70-7.04 respectively). Disease free survival was similar too in the pN0 and pN1micro group, and worse for pN1a and pN≥1b (HR 0.96; 95% CI 0.56-1.67 vs. HR 1.64; 95% CI 1.19-2.27, HR 2.95; CI 1.98-4.42). Distant metastases were more commonly observed in the pN1micro group than in the pN0 group (HR 1.22; 95% CI 0.60-2.49), but not significantly and far less than in the pN1a and pN≥1b group (HR 2.26; 95% CI 1.49-3.40, HR 3.49; 95% CI 2.12-5.77).Conclusion: After a relative long time of follow up disease free and overall survival for patients with micrometastasis in SLNs is comparable to patients without lymphogenic metastasis and more favourable than patients with macrometastasis. The presence of micrometastatic disease in the SLN is in itself not an indication for adjuvant systemic therapy. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 307.