Background Metastasized or unresectable melanoma has been the first malignant tumor to be successfully treated with checkpoint inhibitors. Nevertheless, about 40–50% of the patients do not respond to these treatments and severe side effects are observed in up to 60%. Therefore, there is a high need to identify reliable biomarkers predicting response. Tumor Mutation Burden (TMB) is a debated predictor for response to checkpoint inhibitors and early measurement of ctDNA can help to detect treatment failure to immunotherapy in selected melanoma patients. However, it has not yet been clarified how TMB and ctDNA can be used to estimate response to combined CTLA-4 and PD-1 antibody therapy in metastatic melanoma. Patients and methods In this prospective biomarker study, we included 35 melanoma patients with ipilimumab (anti-CTLA-4) and nivolumab (anti-PD-1) therapy. In all patients, a tumor panel of 710 tumor-associated genes was applied (tumor vs. reference tissue comparison), followed by repetitive liquid biopsies. Cell-free DNA was extracted and at least one driver mutation was monitored. Treatment response was evaluated after about three months of therapy. Results TMB was significantly higher in responders than in nonresponders and TMB > 23.1 Mut/Mb (TMB-high) was associated with a survival benefit compared to TMB ≤ 23.1 Mut/Mb (TMB-low or TMB-intermediate). Furthermore, a > 50% decrease of cell-free DNA concentration or undetectable circulating tumor DNA (ctDNA), measured by tumor-specific variant copies/ml of plasma at first follow-up three weeks after treatment initiation were significantly associated with response to combined immunotherapy and improved overall survival, respectively. It is noticeable that no patient with TMB ≤ 23.1 Mut/Mb and detectable or increasing ctDNA at first follow-up responded to immunotherapy. Conclusion High TMB, > 50% decrease of cell-free DNA concentration, and undetectable ctDNA at first follow-up seem to be associated with response and overall survival under combined immunotherapy. The evaluation of ctDNA and cell-free DNA three weeks after treatment initiation may be suitable for early assessment of efficacy of immunotherapy. Electronic supplementary material The online version of this article (10.1186/s40425-019-0659-0) contains supplementary material, which is available to authorized users.

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Background Central nervous system lymphomas (CNSL) is a devastating disease. Currently, a confirmatory biopsy is required prior to treatment. Objective Our investigation aims to prove the feasibility of a minimally-invasive diagnostic approach for the molecular characterization of CNSL. Methods Tissue biopsies from 6 patients with suspected CNSL were analyzed using a 649gene next-generation sequencing (NGS) tumor panel (tumor vs. reference tissue (EDTA-blood)). The individual somatic mutation pattern was used as a basis for the digital PCR analyzing circulating tumor DNA (ctDNA) from plasma and cerebrospinal fluid (CSF) samples, identifying one selected tumor mutation during this first step of the feasibility investigation. Results NGS-analysis of biopsy tissue revealed a specific somatic mutation pattern in all confirmed lymphoma samples ( n = 5, NGS-sensitivity 100%) and none in the sample identified as normal brain tissue (NGS-specificity 100%). cfDNA-extraction was dependent on the extraction-kit used and feasible in 3 samples, in all of which somatic mutations were detectable (100%). Analysis of CSF-derived cfDNA was superior to plasma-derived cfDNA and routine microscopic analysis (lymphoma cells: n = 2, 40%). One patient showed a divergent molecular pattern, typical of Burkitt-Lymphoma (HIV+, serologic evidence of EBV-infection). Lumbar puncture was tolerated without complications, whereas biopsy caused 3 hemorrhages. Conclusions Our investigation provides evidence that analysis of cfDNA in central nervous system tumors is feasible using the described protocol. Molecular characterization of CNSL could be achieved by analysis of CSF-derived cfDNA. Knowledge of a tumor’s specific mutation pattern may allow initiation of targeted therapies, treatment surveillance and could lead to minimally-invasive diagnostics in the future. Electronic supplementary material The online version of this article (10.1186/s12885-019-5394-x) contains supplementary material, which is available to authorized users.

Knowing the thermal and hydraulic conditions below major urban centers is of increasing importance in the context of energy and water supply. With this study, focusing on the major urban center of Berlin, Germany, we aim to gain insights on the coupling of surface water bodies to the subsurface thermal and hydraulic field investigating shallow water to deep groundwater interactions. Therefore, we use a 3D structural model of the subsurface, constrained by all available data and observations, as a base for simulations of the coupled transport of fluid and heat. This model resolves the 3D configuration of the main geological units and thus enables us to account for related heterogeneities in physical properties. Additionally, we resolve surface water body geometries with newly available data. To assess how surface water bodies interact with the deeper groundwater at different depths in the model domain, the influence of different hydraulic boundary conditions is quantified, which indicates that the coupling of surface water bodies and groundwater strongly modifies predicted groundwater circulation. Consequently, changes in subsurface temperatures are also predicted, where lakes may account for temperature differences up to ±5°C and rivers could account for up to ±1°C visible at depths ≤-500 m.a.s.l. These differences are mainly connected to changes in the advective component of heat transport caused by the modifications of the hydraulic boundary condition. Pressure-driven heat transport is most efficient where differences between hydraulic heads of aquifers and surface water bodies are highest. This study therefore illustrates the impact of surface to subsurface water interactions in an urban context.