Predictive and prognostic value of total tumor load in sentinel lymph nodes in breast cancer patients after neoadjuvant treatment using one-step nucleic acid amplification: the NEOVATTL study

OBJECTIVE: To evaluate the predictive and prognostic value of total tumor load (TTL) in sentinel lymph nodes (SLNs) in patients with infiltrating breast cancer after neoadjuvant systemic therapy (NST). METHODS: This retrospective multicenter study used data from a Spanish Sentinel Lymph Node database. Patients underwent intraoperative SLN biopsy after NST. TTL was determined from whole nodes using a one-step nucleic acid amplification (OSNA) assay and defined as the total sum of CK19 mRNA copies in all positive SLNs. Cox-regression models identified independent predictive variables, which were incorporated into a nomogram to predict axillary non-SLN metastasis, and identified prognostic variables for incorporation into a disease-free survival (DFS) prognostic score. RESULTS: A total of 314 patients were included; most had no lymph node involvement prior to NST (cN0; 75.0% of patients). Most received chemotherapy with or without biologic therapy (91.7%), and 81 patients had a pathologic complete response. TTL was predictive of non-SLN involvement (area under the concentration curve = 0.87), and at a cut-off of 15,000 copies/µL had a negative predictive value of 90.5%. Nomogram parameters included log (TTL + 1), maximum tumor diameter and study-defined NST response. TTL was prognostic of disease recurrence and DFS at a cut-off of 25,000 copies/µL. After a 5-year follow-up, DFS was higher in patients with ≤ 25,000 copies/µL than those with > 25,000 (89.9% vs. 70.0%; p = 0.0017). CONCLUSIONS: TTL > 15,000 mRNA copies/µL was predictive of non-SLN involvement and TTL > 25,000 mRNA copies/µL was associated with a higher risk of disease recurrence in breast cancer patients who had received NST. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12094-020-02530-4.