考虑转移性乳腺癌（MBC）的异质性和结果改善，我们开发了一个分期系统，根据生存结果和与疾病相关的变量，对初次诊断时患有转移性癌症的患者进行了预后估计精细化，即de novo MBC（dnMBC）。从国家癌症数据库（NCDB）中选择了dnMBC患者（2010年至2016年）。采用递归分区分析（RPA）将具有类似总生存期（OS）的患者分组，基于临床T分类、等级、雌激素受体（ER）、孕激素受体、人类表皮生长因子受体2、组织学、转移器官系统部位（仅限骨、仅限脑、脏器）和器官系统涉及数量。三年OS率用于分配最终阶段：IVA：>70％，IVB：50％-70％，IVC：25％至<50％和IVD：<25％。采用1,000次迭代的自举法，根据最常发生的分配进行最终阶段的分配。进行未调整的OS估计。使用SEER和NCDB进行验证分析。在中位随访52.9个月后，原始队列（N = 42,467）的中位OS为35.4个月（95％CI，34.8至35.9）。RPA将患者分成了53个组，3年OS率从73.5％到5.7％不等；将这些组合并为四个阶段组：3年OS，A = 73.2％，B = 61.9％，C = 40.1％和D = 17％（对数秩p <.001）。自启动后，四个阶段的生存结果仍有显着差异（对数秩p <.001）。然后使用SEER数据（N = 20,469）和NCDB的另一组（N = 7,645）进行了验证（两者对数秩p <.001）。我们的研究结果显示，dnMBC患者的异质性结果可指导未来修订新发现IV期患者的当前美国癌症联合委员会分期指南。我们的研究结果应得到独立的确认。

Given the heterogeneity and improvement in outcomes for metastatic breast cancer (MBC), we developed a staging system that refines prognostic estimates for patients with metastatic cancer at the time of initial diagnosis, de novo MBC (dnMBC), on the basis of survival outcomes and disease-related variables.Patients with dnMBC (2010-2016) were selected from the National Cancer Database (NCDB). Recursive partitioning analysis (RPA) was used to group patients with similar overall survival (OS) on the basis of clinical T category, grade, estrogen receptor (ER), progesterone receptor, human epidermal growth factor receptor 2, histology, organ system site of metastases (bone-only, brain-only, visceral), and number of organ systems involved. Three-year OS rates were used to assign a final stage: IVA: >70%, IVB: 50%-70%, IVC: 25 to <50%, and IVD: <25%. Bootstrapping was applied with 1,000 iterations, and final stage assignments were made based on the most commonly occurring assignment. Unadjusted OS was estimated. Validation analyses were conducted using SEER and NCDB.At a median follow-up of 52.9 months, the median OS of the original cohort (N = 42,467) was 35.4 months (95% CI, 34.8 to 35.9). RPA stratified patients into 53 groups with 3-year OS rates ranging from 73.5% to 5.7%; these groups were amalgamated into four stage groups: 3-year OS, A = 73.2%, B = 61.9%, C = 40.1%, and D = 17% (log-rank P < .001). After bootstrapping, the survival outcomes for the four stages remained significantly different (log-rank P < .001). This staging system was then validated using SEER data (N = 20,469) and a separate cohort from the NCDB (N = 7,645) (both log-rank P < .001).Our findings regarding the heterogeneity in outcomes for patients with dnMBC could guide future revisions of the current American Joint Committee on Cancer staging guidelines for patients with newly diagnosed stage IV disease. Our findings should be independently confirmed.