Fig. 3

Spatial and temporal heterogeneity in tumor evolution. A single tumor tissue biopsy is equivalent to taking a mere “snapshot” of the molecular makeup of the tumor at a fixed time. The tumor’s evolutionary history and future as a result of progression and/or treatment would be missing from this single snapshot. Instead, serial and longitudinal tissue biopsies that track and follow the tumor’s development under therapy and during progression would empower more comprehensive and accurate representation of the tumor’s evolution, especially in exposing the conditions surrounding the emergence of subclones (as indicated by the different colors). Identification of subclones with known drug-resistant drivers can better inform the course of treatment most suitable for the tumor at its current state