T1LG（T1低级别）膀胱癌的存在和预后存在争议。另外，由于数据不足，尚不清楚巴斯德卡尔梅特-居雷 (BCG) 治疗的T1LG肿瘤的临床史是什么，以及它是否与其他非肌层浸润性膀胱癌 (NMIBC) 代表有所不同。本研究的目的是分析接受BCG免疫治疗的T1LG膀胱癌患者的无复发生存率（RFS）和无进展生存率（PFS）。 进行了一项使用BCG治疗的2510名Ta/T1 NMIBC患者的多中心和回顾性研究，其中包括有或无原位癌（CIS）的患者（205名T1LG患者）。使用Kaplan-Meier估计和log-rank检验来比较TaLG、TaHG、T1LG和T1HG NMIBC之间的生存情况，分析RFS和PFS。此外，将T1LG肿瘤归类为EAU2021风险组，并进行PFS分析，构建RFS和PFS的Cox多变量模型。 中位随访时间为52个月。对于T1LG队列，5年RFS和PFS率分别为59.3%和89.2%。虽然NMIBC亚群之间的RFS没有差异，但与T1HG相比，T1LG NMIBC的PFS稍好（5年PFS：T1LG对比T1HG：82%对比89%；P<0.001）。当应用EAU 2021预测模型对T1LG NMIBC患者进行异质分类时，发现高风险T1LG患者的PFS显著较差（5年PFS：81.8%），而中间风险（5年PFS：93.4%）和低风险T1LG肿瘤（5年PFS：98.1%）的PFS较好，且差异具有统计学意义。 T1LG的RFS与其他NMIBC亚群相当。T1LG肿瘤的PFS显著优于T1HG NMIBC。EAU2021评分模型对T1LG肿瘤的进展风险进行了异质性分类，高风险T1LG的PFS最差。

The existence and prognosis of T1LG (T1 low-grade) bladder cancer is controversial. Also, because of data paucity, it remains unclear what is the clinical history of bacillus Calmette-Guérin (BCG) treated T1LG tumors and if it differs from other NMIBC (non-muscle-invasive bladder cancer) representatives. The aim of this study was to analyse recurrence-free survival (RFS) and progression-free survival (PFS) in patients with T1LG bladder cancers treated with BCG immunotherapy.A multi-institutional and retrospective study of 2510 patients with Ta/T1 NMIBC with or without carcinoma in situ (CIS) treated with BCG (205 T1LG patients) was performed. Kaplan-Meier estimates and log-rank test for RFS and PFS to compare the survival between TaLG, TaHG, T1LG, and T1HG NMIBC were used. Also, T1LG tumors were categorized into EAU2021 risk groups and PFS analysis was performed, and Cox multivariate model for both RFS and PFS were constructed.The median follow-up was 52 months. For the T1LG cohort, the estimated RFS and PFS rates at 5-year were 59.3% and 89.2%, respectively. While there were no differences in RFS between NMIBC subpopulations, a slightly better PFS was found in T1LG NMIBC compared to T1HG (5-year PFS; T1LG vs. T1HG: 82% vs. 89%; P<0.001). A heterogeneous classification of patients with T1LG NMIBC was observed when EAU 2021 prognostic model was applied, finding a statistically significant worse PFS in patients classified as high-risk T1LG (5-year PFS; 81.8%) compared to those in intermediate (5-year PFS; 93,4%), and low-risk T1LG tumors (5-year PFS; 98,1%).The RFS of T1LG was comparable to other NMIBC subpopulations. The PFS of T1LG tumors was significantly better than of T1HG NMIBC. The EAU2021 scoring model heterogeneously categorized the risk of progression in T1LG tumors and the high-risk T1LG had the worst PFS.