Page 205 - 2021_02-Haematologica-web

ctDNA in cerebrospinal fluid of patients with CNS lymphoma
A
B
C D
E
F
Figure 4. Cerebrospinal fluid (CSF) circulating tumor DNA (ctDNA) detects central nervous system (CNS) involvement and residual disease in patients with systemic lymphoma and is more sensitive than conventional tests. Longitudinal analyses of (A) CSF and (D) plasma ctDNA (VAF values for each mutation detected using ddPCR) and correlation with (B) CSF FC (cells/mL), (C) cytology (+/- presence/absence of cells), and (E) type of treatment and radiological response assessment. (F) Radiological imaging (magnetic resonance imaging [MRI] and positron emission tomography/computed tomography scans) in two patients with systemic lymphoma (NHL16 and NHL17) that present CNS relapse. Data points are vertically aligned. MRI scans for patient NHL17 are not shown given that the patient only presented leptomeningeal involvement. Dx: time of diagnosis; R-CHOP: combined therapy (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone); IT MTX: intrathecal methotrexate; CR: complete response; P: parenchymal; LM: leptomeningeal; EOT: end of treatment; m: month; d: days; NA: not available. *CSF sample was not available for ctDNA analyses
in sequential samples and did not correlate with the disease status, underlining the fact that plasma ctDNA is not useful to monitor the activity of CNS restricted lymphomas (Figure 2).
Six patients with systemic lymphoma without CNS involvement had sequential plasma samples collected at the same time as CSF. We observed that plasma ctDNA became undetectable after the first cycle of treatment in all cases, in agreement with PET/CT results (Figure 2), suggesting that plasma ctDNA is a good tool to monitor response to treat- ment in these patients.
Cerebrospinal fluid circulating tumor DNA can identify central nervous system relapse and residual central nervous system disease better than flow cytometry
We then addressed whether the presence of ctDNA in
the CSF could be more sensitive than conventional CSF analyses to monitor CNS lymphoma and detect CNS relapse.
In two cases of CNS lymphoma (NHL3 and NHL5), we observed that CSF ctDNA levels increased earlier than the detection of cells by FC. In NHL3, after the first dose of IT MTX, despite the fact that the patient did not exhibit a complete neurological response, we observed a sharp decrease in CSF ctDNA levels concomitant with a decrease in the tumor cells by FC. However, after three doses of IT MTX, although FC was negative, a clear ctDNA increase was observed. The patient died 1 month later due to pro- gression (Figure 3). In NHL5, CSF ctDNA levels also decreased with response to treatment and remained unde- tectable after complete remission. However, CSF ctDNA reappeared in two CSF samples collected 2 and 4 months
haematologica | 2021; 106(2)
519