3 Results
Patient characteristics were shown in TABLE 1 . Briefly, a total
of 8 extramedullary relapsed childhood B-ALL patients with the average
age of 7.9 years old (range, 4.3-13.0) were enrolled in this study and
treated at Shanghai Children’s Medical Center (6 patients) and
Children’s Hospital of Soochow University (2 patients). There were 4
patients infiltrated with CNS, 1 with testis, 2 with subcutaneous tumor
and 1 with both CNS and testis. All patients were all relapsed. The mean
time follow-up time was 21.9 months (5.93 to 39.97 months). In addition,
5 of 8 patients (39.4%) relapsed more than once in which merely patient
S003 relapsed after HSCT. Furthermore, all patients received fresh CAR-T
product and the average infusion dose was 9.9×106 per
kilogram of body weight (range, 1.8–15.0).
All 8 patients achieved complete remission (CR), in which 5 patients are
continuous CR, and no CAR-T related death happened. Patients S001 was
bridged to HSCT after the first CR of CAR-T. Patient-level clinical
response outcomes are exhibited in Fig. 1A . The estimated EFS
of patients with 19CAR-T cells was approximately 68.57% at 12 months
and decreased to 51.43% at 24
months. Patients S002, S004 and
S006 were relapsed with CD19+ and CD22+ blasts after prior exposure to
CAR-T cells. Therefore, they sequentially accepted combined CD19 and
CD22 CAR-T cells as a second CAR-T therapy at dose of
1.5×107, 4.26×106 and
1.2107 per kilogram of body weight, respectively
(TABLE 2 ). Then, all of them achieved CR again (CR2). To date,
none of them chose bridging to HSCT after the second CAR-T.
Except patient S006, CRS was observed in all patients. 3 in 8 patients
were grade 3~4. CAR-T related encephalopathy syndrome
(CRES) was observed in 6 patients (75%) and no grade
3~4 CRES was identified. 4 patients received the
tocilizumab, in which 2 patients also received glucocorticoids
simultaneously. Only patient S004 received glucocorticoids intrathecal
injection alone. No patient died of severe CRS or CRES (TABLE
2 ). Interleukin 6 (IL-6) and interferon γ (IFNγ) concentrations are
main biomarkers of CRS severity. Similar patterns were observed in both
IL-6 and IFNγ (Fig. 2A ), the highest level of IL-6 was 60618.45
pg/ml detected in patient S003 (TABLE 2 ). At day 7, transient
increases in levels of serum IL-6 and IFNγ occurred in most patients
during CRS after CAR-T administration. We also observed that a drop of
IL-6 was always followed with a lift of lymphocytes in peripheral blood
(Fig. 2B ), which was
temporally in accordance with the
resolution of CRS.
Different from the symptoms of testicular infiltration after
chemotherapy, patients had fever and the affected testis showed
progressive redness and swelling 3~4 days after CAR-T
infusion, and patient may have a little pain. Although the testicle was
swollen, it feels soft by physical palpation. The swelling testis
reached the most serious situation in about a week, then began to
decrease and continue to soften gradually until it turned close to
normal size.
Patients with CNS involvement had more severe symptoms of encephalopathy
manifested as high fever, headache, frequent vomiting, drowsiness,
unconsciousness, hypotension or hypertension, limb trembling,
convulsions. For patient with convulsions, lumber puncture was required,
and the cerebrospinal fluid (CSF) protein increased significantly,
meanwhile, the IL-6 concentration in CSF was much higher than that in
peripheral blood. For example, on day 6, patient S004 suffered 1272.27
pg/ml of IL-6 in CSF whereas 26.62 pg/ml in peripheral blood. We also
detected higher level of CAR gene in CSF compared with peripheral blood.
In patient S005, 465.026×103 copies CAR per ug DNA was
detected, which was over 10 times more than that detected in peripheral
blood on day 3 (Fig. 2C ). Additionally, CAR-T cells expansion
were determined by real-time qPCR and the result showed that the peak
CAR-T expansion was variable in different EM relapsed patients but not
observed after Day 7 (Fig. 2D ).