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S. Bobillo et al.
after treatment due to the presence of minimal neurological symptoms, when brain-spinal MRI and CSF FC did not show any evidence of disease; 8 months later CNS relapse was confirmed (Figure 3). Taken together, our results indi- cate that ctDNA can be a more sensitive tool than FC to monitor relapse of CNS lymphomas.
In one additional case of CNS lymphoma (NHL6) treat- ment with IT MTX decreased the number of cells in the CSF till they were no longer detectable by FC. However, CSF ctDNA was still detectable. Notably, this patient relapsed shortly after the analysis (Figure 3). In a similar way, we found persistence of ctDNA in the CSF from case NHL17 after treatment for CNS relapse, despite the fact that FC did not detect malignant cells. Four months later, the patient relapsed. (Figure 4). These results point out that the detection of CSF ctDNA may help to identify patients with residual disease who are likely to relapse.
A subset of patients with systemic lymphoma presents high risk of CNS relapse, which frequently occurs during treatment or shortly thereafter. To address whether the presence of CSF ctDNA could be more sensitive than FC to detect CNS disease, we analyzed sequential CSF sam- ples from eight patients with systemic lymphoma obtained while receiving prophylactic IT MTX. Two out of 8 patients relapsed in the CNS during the time of study (Figure 4). In one case (NHL17), we found CSF ctDNA at the same moment in which FC showed a positive result. However, we could not detect ctDNA in the CSF samples collected 9 and 7 months before CNS progression. Notably, in case NHL16, the detection of ctDNA in the CSF with a VAF of 7% antedated by 3 months the CNS relapse. Importantly, at the time of ctDNA detection, the patient was asymptomatic and CSF FC was normal (Figure 4). This case points out that CSF ctDNA could detect CNS involvement in systemic lymphomas earlier than standard procedures. Finally, in the remaining six patients with systemic lymphoma and sequential CSF samples, ctDNA was not detected and, with a median fol- low-up of 18 months (range: 12-28 months), these patients did not develop CNS disease.
Discussion
The diagnosis and monitoring of CNS lymphoma are still challenging. MRI can be misleading and not suffi- ciently sensitive, and the difficulties of the intracranial tumor biopsies challenge histological diagnosis. Mutational analysis of the CSF could be useful in these cases, since the presence of MYD88 L265P mutation strongly suggests the diagnosis of PCNSL.13,14,16-18 Ours is a proof of concept study aiming to identify and character- ize ctDNA in the CSF of patients with CNS lymphoma and to evaluate its role in the management of these patients. We were able to identify ctDNA in the CSF from all patients with restricted CNS disease and show that CSF ctDNA could complement the diagnosis, identify somatic mutations, monitor tumor burden and response to treatment, and facilitate early detection of relapse, as well as detect residual disease after treatment. In addi- tion, our results support the notion that the CSF is a bet- ter source of ctDNA than plasma.
Assessment of therapeutic response in CNS lym- phomas is usually performed by brain MRI along with FC
and cytology. Regrettably, around 50-60% of patients with CNS lymphoma will eventually relapse.21 Notably, we observed that CSF ctDNA was able to detect CNS lesions better than FC and cytology. In addition, CSF ctDNA was able to predict CNS relapse months before MRI or FC, indicating that it can be used for early detec- tion of tumor relapse.
CNS relapse from systemic lymphoma is a fatal compli- cation with an overall survival of less than 6 months, and early identification of patients with CNS relapse is of para- mount value.3 High-risk patients are usually tested for CNS disease by CSF analysis including cytology and FC. Although FC is a more sensitive test than conventional cytology,5,6 it has some limitations22 and some patients with no evidence of CNS disease by FC still relapse, suggesting the presence of undetected malignant cells in the CSF. We identified ctDNA in the CSF in the absence of MRI or FC detection earlier than CNS relapse. This indicates that CSF ctDNA could facilitate early detection of CNS relapse in high-risk systemic lymphomas who undergo serial lumbar punctures to administrate prophylactic IT chemotherapy, therefore improving management of these patients.
Moreover, we observed the persistence of high levels of CSF ctDNA in some patients even though FC did not detect tumor cells. This suggested that the detection of a residual disease by CSF ctDNA could be used to deter- mine the type and duration of treatments.
Taken together, and with the limitation of the reduced number of patients analyzed, our findings show that CSF ctDNA can be an important tool to complement standard procedures to evaluate the CNS lymphoma disease sta- tus. This technology can be exploited as a 'liquid biopsy' of CNS lymphoma opening a novel way forward for research in circulating biomarkers of CNS lymphoma with an important impact on the future characterization, diagnosis, prognosis, and management of this type of dis- eases.
Disclosures
JS is a co-founder of Mosaic Biomedicals and Northern Biologics. JS received grant/research support from Mosaic Biomedicals, Northern Biologics and Roche/Glycart. M. C. has received research funding from Karyopharm, Pharmacyclics, Roche, Arqule and AstraZeneca. Francesc Bosch has received research funding and honoraria from Roche, Celgene, Takeda, AstraZeneca, Novartis, Abbie and Janssen. All remaining authors have declared no conflicts of interest.
Contributions
SB, MC, LE, FB and JS contributed equally.
Funding
This work was supported by research funding from Fundación Asociación Española contra el Cáncer (AECC) (to JS, MC and PA); FERO (to JS), laCaixa (to JS), BBVA (CAIMI) (to JS), the Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias (PI16/01278 to JS; PI17/00950 to MC; PI17/00943 to FB) co- financed by the European Regional Development Fund (ERDF) and Gilead Fellowships (GLD16/00144, GLD18/00047, to FB). MC holds a contract from Ministerio de Ciencia, Innovación y Universidades (RYC-2012-12018). SB received funding from Fundación Alfonso Martin Escudero. LE received funding from the Juan de la Cierva fellowship. We thank CERCA Programme / Generalitat de Catalunya for institutional support.
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haematologica | 2021; 106(2)