Objectives: The incidence of renal cell carcinoma (RCC) has been rising, largely due to increased incidental detection from widespread imaging. Although synchronous distant metastasis (SM) with a primary renal tumor measuring <4 cm (cT1a) is uncommon, its presence may influence survival outcomes and the utility of cytoreductive nephrectomy. We sought to investigate clinical characteristics, metastatic patterns, treatments, and survival outcomes of patients with T1a RCC. Methods: All patients aged ≥18 years diagnosed with RCC between 2004 and 2019 were extracted from the National Cancer Database. The Cochran–Armitage test was used for trend analysis, while multivariable analyses were conducted to identify variables associated with SM and to assess the impact of cytoreductive surgery on mortality across isolated metastatic sites. Kaplan–Meier analysis was performed to compare survival outcomes. Results: A total of 263,911 individuals diagnosed with T1a RCC were analyzed in the study. Among them, 114,661 patients (43.4%) were classified as having cT1a tumor stage, and of these patients with cT1a RCC, 2275 (2.0%) exhibited SM. The proportion of SM cT1a was 3.39% in 2004 and 2.08% in 2019, with an Average Annual Percent Change (AAPC) of −0.037% (p= 0.830). The most common sites of metastasis were bone (59%), followed by lung (35%), liver (16%), and brain (12%). Resection of the primary tumor and receipt of systemic therapy were significantly associated with reduced mortality among all metastatic sites, especially in individuals with lung-only metastases (HR = 0.02,p= 0.013). Metastasectomy was associated with improved survival in patients with brain-only metastases (HR = 0.26,p= 0.006) but did not demonstrate the same benefit in patients with bone-, lung- or liver-only metastases. The worst 5-year OS rate was observed in cases with metastasis to multiple sites, whereas isolated metastases had similar survival rates (p< 0.0001). Our findings are limited by retrospective study design. Conclusions: This comprehensive analysis of T1a RCC patients reveals that while synchronous metastasis is relatively uncommon (2.0%), it presents significant clinical challenges, with bone as the most common metastatic site, contrasting with the typical lung predominance in larger tumors. Primary tumor resection showed survival benefit in patients with isolated metastases, especially for lung-only metastasis. These findings highlight the heterogeneous nature of tumor biology in small renal masses and underscore the importance of tailored, multimodal treatment strategies for the effective management of SM T1a RCC.
目的：肾细胞癌（RCC）的发病率持续上升，主要归因于影像学检查普及带来的偶发性检出增加。虽然原发性肾肿瘤直径<4 cm（cT1a）伴同时性远处转移（SM）的情况并不常见，但其存在可能影响生存结局及减瘤性肾切除术的临床价值。本研究旨在探讨T1a期RCC患者的临床特征、转移模式、治疗方案及生存结局。方法：从美国国家癌症数据库中提取2004年至2019年间所有年龄≥18岁的RCC确诊患者数据。采用Cochran-Armitage检验进行趋势分析，通过多变量分析确定与SM相关的变量，并评估减瘤手术对不同孤立转移部位患者死亡率的影响。采用Kaplan-Meier法比较生存结局。结果：本研究共纳入263,911例T1a期RCC确诊患者。其中114,661例（43.4%）被归类为cT1a肿瘤分期，而在这些cT1a RCC患者中，2275例（2.0%）存在SM。SM cT1a的比例从2004年的3.39%下降至2019年的2.08%，年均变化百分比（AAPC）为-0.037%（p=0.830）。最常见的转移部位是骨骼（59%），其次是肺（35%）、肝脏（16%）和脑（12%）。在所有转移部位中，原发性肿瘤切除联合全身治疗均与死亡率降低显著相关，尤其在单纯肺转移患者中最为明显（HR=0.02，p=0.013）。转移灶切除术可改善单纯脑转移患者的生存（HR=0.26，p=0.006），但在单纯骨、肺或肝转移患者中未观察到同等获益。多部位转移患者的5年总生存率最差，而孤立转移患者的生存率相近（p<0.0001）。本研究的局限性在于回顾性研究设计。结论：这项针对T1a期RCC患者的综合分析表明，虽然同时性转移相对少见（2.0%），但构成显著的临床挑战，其中骨骼是最常见的转移部位——这与较大肿瘤中典型的肺转移优势形成对比。原发性肿瘤切除在孤立转移患者中显示出生存获益，尤其对单纯肺转移患者。这些发现揭示了小肾肿块肿瘤生物学的异质性，并强调了制定个体化、多模式治疗策略对有效管理SM T1a期RCC的重要性。
Characteristics and Outcomes of T1a Renal Cell Carcinoma Presenting with Metastasis
肿瘤(癌症)患者之家