Figure 1.

Defining patient similarity. These diagrams represent the clinical courses of 3 hypothetical patients with non-small cell lung cancer. Patient A corresponds to a patient who was diagnosed with early stage disease, who underwent surgery and adjuvant chemotherapy and, so far, has not developed recurrent disease. Patient B had a trajectory that began similarly but developed cancer recurrence, leading their oncologist to order tumor genomic sequencing and prescribe immunotherapy. Patient C had metastatic disease at diagnosis which was treated initially with chemotherapy and, subsequently, with immunotherapy. Any definition of similarity among these patients must necessarily be time-dependent; early in the cancer trajectory, patients A and B are most similar, but later in the trajectory, patients B and C are most similar.