External validation of a prognostic model based on total tumor load of sentinel lymph node for early breast cancer patients

• DOI: 10.1007/s10549-020-05623-4
• Publication Date: 2020-04-06T08:04:41Z
• Authors: Antonio Piñero-Ma...; Francisco Ripoll-...; José Ignacio Sánc...; Asunción Chaves-B...; Maximiliano Rodri...; Ana Calatrava-Fons; Salomón Menjón-Be...; Vicente Peg-Cámara
• Keywords: 0301 basic medicine; Models, Statistical; Medicina; Sentinel Lymph Node Biopsy; Model validation; Breast Neoplasms; Middle Aged; Prognosis; Clinical Trial; Tumor Burden; 3. Good health; Survival Rate; 03 medical and health sciences; Breast cancer; Humans; Female; Sentinel Lymph Node; Sentinel lymph node; Total tumor load; Follow-Up Studies; Retrospective Studies

Abstract Background A prognostic model based on the results of molecular analysis of sentinel lymph nodes (SLN) is needed to replace the information that staging the entire axilla provided. The aim of the study is to conduct an external validation of a previously developed model for the prediction of 5-year DFS in a group of breast cancer patients that had undergone SLN biopsy assessed by the One Step Nucleic Acid Amplification (OSNA) method.

Methods We collected retrospective data of 889 patients with breast cancer, who had not received systemic treatment before surgery, and who underwent SLN biopsy and evaluation of all SLN by OSNA. The discrimination ability of the model was assessed by the area under the ROC curve (AUC ROC), and its calibration by comparing 5-years DFS Kaplan–Meier estimates in quartile groups of model predicted probabilities (MPP).

Results The AUC ROC ranged from 0.78 (at 2 years) to 0.73 (at 5 years) in the training set, and from 0.78 to 0.71, respectively, in the validation set. The MPP allowed to distinguish four groups of patients with heterogeneous DFS (log-rank test p < 0.0001). In the highest risk group, the HR were 6.04 [95% CI 2.70, 13.48] in the training set and 4.79 [2.310, 9.93] in the validation set.

Conclusions The model for the prediction of 5-year DFS was successfully validated using the most stringent form of validation, in centers different from those involved in the development of the model. The external validation of the model confirms its utility for the prediction of 5-year DFS and the usefulness of the TTL value as a prognostic variable.