Fig. 4

Use cases for ctDNA analysis throughout the cancer patient journey: disease monitoring. A Representation of 3 real-world cases of patients who underwent serial liquid biopsy sampling for disease monitoring purposes via shallow whole-genome sequencing (sWGS). Patient age and tumor entity are displayed in the white box. In the green panels, the NGS results from sWGS monitoring are shown in patient timelines. The serial samples are listed in the gray boxes (e.g. S1, S2, etc.). Detected focal somatic copy number alterations (SCNAs) are shown in the green callout boxes at the corresponding time point that they were detected via sWGS.B Basic decision tree for this use case and the interpretation of detected alterations from disease monitoring data via liquid biopsy. The cases in (A) are mapped at the corresponding position that reflects the individual scenario. Again, assessment of the ctDNA level in plasma represents the critical first step, as decreases in ctDNA from the previous sample may indicate a response to therapy, whereas unchanged levels may indicate stable disease. Increases in ctDNA fraction are generally associated with progressive disease. In some cases, novel alterations may be detected via monitoring and may represent novel druggable targets that were not observed from previous profiling (Case 1), known resistance markers (Case 2), or a clonal switch, which demonstrates the adaptive nature of tumors under the selective pressure of targeted therapies (Case 3)