To the best of our knowledge, this is one of the few studies that used SEER database to examine the survival and demographic characteristics of SCNEC. Furthermore, the research emphasized the predictive significance of adjuvant therapy and furnished a clinical therapeutic reference. Mollica et al. (Mollica et al. 2022) analyzed the survival data of patients with high-grade neuroendocrine bladder tumors in the SEER database. Their study reported that the median OS time was 12 months, which matched the current study’s results (13 months). The results indicated that the Grade stage does not significantly affect prognosis, which is also consistent with the results of the univariate regression analyses in the present study. Jung et al. (Jung et al. 2017) reported that the 5-year survival rate of SCNEC patients was 14%, which is significantly lower than the present study (21.2%). The difference could be caused by treatment modalities.
Increasing age has been linked to a higher incidence and a poorer prognosis of many cancers. Previous research indicated that age was an independent predictive factor for breast, lung, bladder, and prostate cancers (Barone et al. 2022; Howard and Pearson 2020; Keegan et al. 2023; Zhang et al. 2022). Feng et al. (Feng et al. 2015) reported that elderly patients usually had worse OS and CSS compared with young patients. In this study, the findings of univariate and multivariate Cox regression analysis also indicated that increasing age was associated with worse OS and CSS.
The T stage (the depth of infiltration), the N stage (the lymph node status) and the M stage (the metastatic status) are the three components that form the foundation of the AJCC staging system is based on three elements. Yang et al. (Yang et al. 2020) constructed a prediction model and indicated that a lower T stage was associated with better survival in patients who underwent radical resection. The results are consistent with the conclusion of this paper. However, Zhang et al. (Zhanghuang et al. 2023) reported that the N stage was not an independent prognostic factor for OS and CSS, which is inconsistent with our results. The difference may be caused by the selection of patients. This study focused on small cell carcinoma, which is a highly malignant type among bladder cancers. Zhang et al. (Zhanghuang et al. 2023) also indicated that patients with developed distant metastases had worse OS and CSS, which is inconsistent with our conclusions.
The current treatment methods for bladder cancer are mainly surgical resection, chemotherapy, and radiotherapy. However, the rarity of SCNEC has made it difficult to establish a standard therapeutic protocol. Cattrini et al. (Cattrini et al. 2019) found that surgical treatment could improve patients’ survival compared with conservative treatment. Similar findings were also found in this current study. In addition, chemotherapy is still the primary treatment method for SCNEC patients. Chau et al. (Chau et al. 2021) and Lim et al. (Lim and Sundar 2019) reported that chemotherapy can significantly improve the prognosis of SCNEC patients. In this study, the results of Cox regression analysis and KM curve analysis revealed that the patients who received chemotherapy had higher OS and CSS, which aligns with the findings of Chau et al. and Lim et al. The use of radiotherapy in SCNEC is rare. Currently, the clinical practice mainly refers to the treatment regimen of pulmonary neuroendocrine carcinoma. Mariniello et al. (Mariniello et al. 2016) published a study on treating advanced small-cell neuroendocrine carcinoma of the lung with peptide-receptor radionuclides. In their study, the median progression-free survival was 28 months, and the median overall survival was 59 months. The study also indicated that treatment with peptide receptor radionuclide in the early stages of the disease could provide more favorable outcomes. In addition, Meijer et al. (Meijer et al. 2013) concluded that radiotherapy was effective in patients with distant metastasis. However, the results of the study indicated that postoperative radiotherapy significantly decreased the OS of patients with the M0 stage or T1-2 stage. The discrepancy may be caused by disease variability or individual differences. Further studies are still needed to identify the optimal use of radiotherapy and to explore whether radiotherapy may improve patients’ survival.
There are some limitations of this study. Firstly, the results of laboratory tests could not be acquired from the SEER database. It is worth noting that elevated lactate dehydrogenase (Lee et al. 2019; Shatagopam et al. 2015) and hypoalbuminemia (Baralo et al. 2023) were also prognostic factors. Secondly, information on targeted therapies and radiotherapy regimens could not be acquired from the SEER database. In addition, patients' conditions and comorbidities could also affect treatment decisions. Finally, this is a retrospective study, and selection bias could not be avoided. The conclusions need to be further validated by prospective studies.