Prognostic Features and Predictive Model for Mixed Invasive Ductal and Lobular Breast Carcinoma in Early-Stage Patients.

INTRODUCTION

Mixed invasive ductal and lobular breast carcinoma (IDLC) is a rare and understudied subtype of breast cancer with unique prognostic characteristics.

METHODS

This study analyzed data from the SEER database and the METABRIC database. Survival outcomes of IDLC were compared with those of IDC and ILC using Kaplan-Meier survival curves and Cox regression analyses. Based on these findings, a prognostic model tailored for IDLC patients was developed using the SEER cohort, which was divided into a training set (70%) and an internal validation set (30%). The model incorporated clinical and molecular features and was externally validated using the METABRIC cohort. Its performance was assessed via C-index, AUC, calibration curves, and decision curve analysis (DCA).

RESULTS

A total of 26,138 early-stage IDLC patients were included, along with 391,888 IDC and 47,571 ILC patients. In unadjusted analyses, IDLC showed better overall survival (OS) and breast cancer-specific survival (BCSS) compared to both IDC and ILC. However, after multivariate adjustment, the differences in survival outcomes varied. IDLC demonstrated better OS than IDC and better BCSS than ILC. Additionally, a prognostic model for early-stage IDLC that incorporates clinical and molecular features was developed.

CONCLUSION

This study found that early-stage IDLC had superior BCSS and OS in unadjusted analyses. However, after multivariate adjustment, there was no difference in BCSS between IDLC and IDC, and no difference in OS between IDLC and ILC. A prognostic model was developed and validated, offering precise predictions of OS and BCSS.