嵌合抗原受体（CAR）T细胞疗法是儿科复发性B淋巴细胞急性淋巴细胞白血病（B-ALL）的有效治疗方法，但是其挑战在于高出CAR之后复发的比例。有关特定复发模式和CAR后涉及非骨髓（EM）部位的文献描述仍然有限，并且CAR后疾病监测的临床标准尚未建立。我们强调将外周血微小残余疾病（MRD）测试和放射影像学整合到监测策略中的重要性，以有效地表征和捕获CAR后复发。在此，我们介绍一个复发严重的B-ALL儿童的病例，在CAR后复发并出现明显的非相邻骨髓和EM疾病。有趣的是，在骨髓穿刺（MRD＜0.01％）呈阴性的情况下，她的复发最初是通过外周血流式细胞术MRD监测检测出来的。18F-氟脱氧葡萄糖正电子发射断层扫描揭示了弥漫性白血病，伴随着无数的骨髓和淋巴结病变，有趣的是，她的骶骨，即骨髓穿刺采样的部位却没有病变。我们强调此病例，因为与标准骨髓穿刺测试相比，外周血MRD和18F-氟脱氧葡萄糖正电子发射断层扫描成像对于检测该患者的CAR后复发更为敏感。临床/生物学见解：在多次复发B-ALL中，复发模式可能包括斑块状骨髓和/或EM疾病，在患者亚组中，使用外周血MRD和/或全身影像可能比标准骨髓采样具有更高的检测灵敏度。©作者（或其雇主）2023年。在CC BY-NC许可下允许再利用。没有商业再利用。由BMJ出版。

Chimeric antigen receptor (CAR) T cell therapy is an effective salvage therapy for pediatric relapsed B-cell acute lymphoblastic leukemia (B-ALL), yet is challenged by high rates of post-CAR relapse. Literature describing specific relapse patterns and extramedullary (EM) sites of involvement in the post-CAR setting remains limited, and a clinical standard for post-CAR disease surveillance has yet to be established. We highlight the importance of integrating peripheral blood minimal residual disease (MRD) testing and radiologic imaging into surveillance strategies, to effectively characterize and capture post-CAR relapse.Here, we describe the case of a child with multiply relapsed B-ALL who relapsed in the post-CAR setting with gross non-contiguous medullary and EM disease. Interestingly, her relapse was identified first from peripheral blood flow cytometry MRD surveillance, in context of a negative bone marrow aspirate (MRD <0.01%). Positron emission tomography with 18F-fluorodeoxyglucose revealed diffuse leukemia with innumerable bone and lymph node lesions, interestingly sparing her sacrum, the site of her bone marrow aspirate sampling.We highlight this case as both peripheral blood MRD and 18F-fluorodeoxyglucose positron emission tomography imaging were more sensitive than standard bone marrow aspirate testing in detecting this patient's post-CAR relapse. Clinical/Biologic Insight: In the multiply relapsed B-ALL setting, where relapse patterns may include patchy medullary and/or EM disease, peripheral blood MRD and/or whole body imaging, may carry increased sensitivity at detecting relapse in patient subsets, as compared with standard bone marrow sampling.© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.