目的·总结接受伊马替尼治疗后符合停药标准的慢性髓系白血病（chronic myeloid leukemia，CML）慢性期（chronic phase， CP）患者在规范监测下尝试无治疗缓解（treatment-free remission，TFR）的结局，并分析可能影响TFR的预后因素和微滴式数字聚合酶链式反应（droplet digital polymerase chain reaction，ddPCR）在TFR监测中的作用。方法·对入组CML-CP患者在停药后定期进行规范监测。通过定量聚合酶链式反应（quantitative polymerase chain reaction，QPCR）检测BCR-ABL转录本评估分子学反应和复发；采用流式细胞仪检测淋巴细胞亚群，分析其对TFR的影响；采用ddPCR检测BCR-ABL，分析其在TFR中的预示作用。结果·① 42例符合停药标准的CML-CP患者，中位随访时间41（5~93）个月；32例（76.2%）患者仍维持TFR状态。12、24和48个月的预期TFR率分别为85.1%、75.1%和70.1%。中位TFR时间为41（2~93）个月。停药后最常见的不良反应为肌肉关节疼痛（31.0%），均为Ⅰ~Ⅱ级。可评估的8例重启治疗患者100%达深层次分子学反应（deep molecular response，DMR）。②停药后持续ddPCR阳性的患者中，7例（58.3%）出现分子学复发，而ddPCR结果为阴性的患者均未出现复发（P<0.01）。③停药前复发组的CD8⁺CD28^-细胞百分比低于TFR组（6.2% vs 12.6%，P=0.026），停药后复发组CD4⁺CD25⁺细胞百分比高于TFR组（3.2% vs 2.1%，P=0.021）。结论·长期持续接受伊马替尼治疗，并符合停药标准的CML-CP患者可以获得持续的TFR；ddPCR有助于提示TFR的预后，并更早识别可能发生分子学复发的患者；不同的T细胞亚群可能在TFR过程中参与了免疫调节以防止CML疾病复发。

Objective ·To analyze the outcomes of treatment-free remission (TFR) after imatinib discontinuation in patients with chronic myeloid leukemia in chronic phase (CML-CP) who meet the criteria for TFR and are willing to monitor the disease regularly, the prognostic factors and the application of droplet digital polymerase chain reaction (ddPCR) technique in monitoring TFR. Methods ·The patients with CML-CP enrolled in this study were monitored regularly after imatinib discontinuation. Molecular response and relapse were analyzed by quantitative polymerase chain reaction (QPCR) for detection of BCR-ABL transcripts. The lymphocytes subsets pre- and post-imatinib discontinuation were evaluated by flow cytometry. ddPCR was used to detect BCR-ABL and the predictive role in TFR was analyzed. Results ·① Forty-two CML-CP patients who met the criteria for TFR were assessed. With median follow-up time 41(5?93) months, 32 (76.2%) patients maintained TFR.The estimated TFR rate by 12, 24 and 48 months were 85.1%, 75.1% and 70.1%, respectively. Median TFR duration was 41 (2?93) months. The most common adverse event post-discontinuation was musculoskeletal pain of grade Ⅰ?Ⅱ (31.0%). Eight patients achieved deep molecular response (DMR) after restart of imatinib. ②58.3% of patients with continuous positive ddPCR developed molecular relapse after imatinib discontinuation, while none relapsed in those with negative detection (P<0.01). ③ The percentage of CD8⁺CD28^- cells pre-discontinuation was lower, while the percentage of CD4⁺CD25⁺ cells post-discontinuation was higher in relapsed patients than that in TFR patients (6.2% vs 12.6%, P=0.026; 3.2% vs 2.1%, P=0.021). Conclusion ·CML-CP patients who meet the criteria of TFR may successfully maintain TFR after TKI discontinuation. ddPCR may help to predict the outcome of TFR and detect the molecular relapse earlier. Immune regulation by different T cell subsets may play a role in TFR duration to prevent relapse of disease.