Predictive factors on outcomes in metaplastic breast cancer

Metaplastic breast cancer (MBC) is a rare, aggressive variant of breast cancer, with limited data available regarding treatment and outcomes. This study aims to review patients with MBC treated at our tertiary care institution with an emphasis on the role of treatment modality and histologic classification.

With IRB-approval, we queried our pathology database for patients with MBC diagnosis. All cases were re-evaluated by dedicated breast pathologists and confirmed as MBC breast cancer. Patient demographics, clinical/pathologic histology, and treatment were analyzed with respect to outcomes including local-regional recurrence (LRR), distant metastasis (DM), and overall survival (OS). Univariate and multivariate Cox proportional hazards models were performed to evaluate the impact on outcomes. Kaplan-Meier methods estimated survival.

We evaluated 113 patients with MBC diagnosed between 2002 and 2013. Median age was 61 years and median pathologic tumor size 2.5 cm; 76 (67%) were ER/PR/Her2 negative, 83 (74%) grade 3. Median follow-up was 38 months. 47 (42%) underwent breast conservation therapy (BCT), 66 (58%) had mastectomy, 61 (54%) underwent adjuvant radiation (RT), and 85 (75%) had chemotherapy. At 2 and 5 years, the LRR/DM/OS rates were 12%/15%/90% and 21%/35%/69%, respectively. On Cox regression analysis, only adjuvant RT correlated with reduced LRR [RR 3.1 (1.13-9.88), p = 0.027], while chemotherapy, type of surgery, and T-N stage did not. Only T-stage (p = 0.008) correlated with DM, however chemotherapy, RT, surgery type, and N-stage were not. Univariate analysis demonstrated histologic subtype did not significantly correlate with local (p = 0.54) or distant (p = 0.83) disease control.

This study represents among the largest institutional experiences in the outcomes of MBC. At this time, there does not appear to be a clear histologic subset of MBC which has significantly different clinical outcomes from the other subtypes. Although limited in its sample size, this study shows RT remains important in local-regional control.