Metaplastic breast cancer (MBC) is a kind of heterogenous breast cancer, which is relatively rare in clinical practice. Although some studies have reported the risk factors related to the survival of MBC patients[6-8], there is no recognized prognostic factors to predict the prognosis of MBC. Paul Wright et al.[9] found that for patients with positive or negative hormone receptors, there was no significant difference in the 5-year survival rate of MBC, which indicated that the status of hormone receptors could not be considered as a prognostic factor of MBC. Additionally, previous study demonstrated that the subtype of MBC could be an independent predictor of its prognosis[3]. Several studies revealed that the prognosis of MBC patients with larger tumor and lymph node metastasis are generally poor[6, 10]. In recent years, some studies have also focused on the relationship between gene signatures and prognosis of MBC patients, such as the high expression of RPL39[6, 10] and the mutation of the colony stimulating factor 1 receptor (CSF1R)[11], all of which can indicate poor prognosis. However, single prognostic factors play a limited role in predicting individual survival probability. Nomograms are graphical display of mathematical models for predicting cancer risk, prevention and therapeutic outcomes, which becomes increasingly popular clinical decision aids due to their ability to handle complexity in a systematic, unbiased manner[12-14]. It has been revealed that nomograms exhibited more excellent prediction precision and prognostic value in diverse malignancies than the existing tumor system[15, 16]To construct a prognostic nomogram, we performed univariate and multivariate Cox proportional-hazards regression analyses to find clinical characteristics that correlated with the OS and CSS of MBC patients on the basis of a large data set from the SEER database. We demonstrated that several clinicopathological characteristics were independent prognostic factors for OS, including age, grade, TNM stage, T stage, N stage, surg_prim_site, chemotherapy and radiotherapy. Furthermore, age, TNM stage, T stage, N stage, chemotherapy and radiotherapy were identified as independent prognostic factors for OS via multivariate analysis. In addition, grade, TNM stage, T stage, N stage, surg_prim_site and radiotherapy were found to be associated with CSS via univariate analysis, and further multivariate analysis confirmed that TNM stage, T stage, N stage and radiotherapy were independent prognostic factors for CSS of MBC patients. The nomograms established in this study showed favorable discrimination and calibration for 3-year and 5-year OS and CSS of MBC patients and offered a more accurate and personalized clinical tool for prognosis evaluation of MBC patients.
Most of the prognostic studies of MBC have been small and with conflicting results or included non-validated cases from population based databases[15, 16]. In this large cases of MBC we have critically assessed the prognostic value of known prognostic variables. The clinical significance of age, TNM stage, T stage, N stage, chemotherapy, radiotherapy in MBC patients were highlighted in nomogram models. The result demonstrated that half of patients were >60 years of age, who suffered worst survival and poor OS. Of note, age showed no significant influence on CSS. Patients with older age generally accompanied a higher-risk histological phenotype[28], which has been identified as an independent risk factor and may eventually result in lower survival [28]. In this study, surgical resection of the primary site remained the mainstay of therapy, with mastectomy more than lumpectomy, which was consistent with previous study[32]In addition, we found that chemotherapy is an independent prognostic factor for OS in MBC patients. Although it is correlated with CSS in univariate analysis, it is not an independent prognostic factor for CSS. It may results from the lower response rates to chemotherapy regimens in MBC[18, 22, 24, 33, 34]. Several studies have concluded that radiotherapy, as part of a multimodal treatment, could improve survival of MBC patients. Similarly, our multivariate results demonstrated that radiation was independently associated with lower HR in patients who received radiotherapy[25, 35, 36]. Moreover, radiotherapy was revealed to be able to reduce the risk of local recurrence[37]. T stage represents the tumor size and extrathyroidal extension, and our results demonstrated that T4 have an impact on OS and CSS in MBC patients, which was in line with previous population-based studies of MBC [35]. LNM has been identified as a key prognostic indicator for a variety of malignancies, and the number of LNM has been included into the N-staging. Previous studies reported that lymph node status was significantly correlated with survival endpoints in patients with MBC [38, 39]There were several potential shortcomings in this study. First, retrospective data retrieved from the same database was used in the construction and validation of the nomograms, which may result in the risk of potential selection bias. Therefore, it would be more reliable to validate the nomograms in another dataset. Second, in this study, we only included two endpoints: 3- and 5-year survival. However, the assessment of recurrence risk is believed to be more meaningful than death because of the rare specific mortality of MBC, which was not performed in this study owing to the lack of data with respect to recurrence in SEER database. Moreover, several other crucial prognostic factors, such as RET mutation status and calcitonin doubling times, were also unavailable in the SEER database