CTC counts during the clinical course and treatment of Patients 16 and 19, since initiation of treatment. Orange and blue bars represent periods when patients were receiving inhibitor therapy, either avelumab or pembrolizumab and radiation respectively. Green dotted line represents the healthy threshold of 1.32 CTCs/mL above which patients are defined as positive for CTCs. Blue marker indicates the CTC number at the time of blood collection, with indication of PD-L1 positive and negative CTCs. The red circle marker indicates the tumor burden, i.e. the index tumor lesions summed cross-sectional area. (Top) In Patient P19, tumor burden initially decreased over time indicating a shrinking of the right upper lobe tumor and a potential response of the patient to the treatment. However, the patient soon after was found on imaging to have developed metastases to the brain and lung, which was preceded by the increase of CTC number from 0.67 to 9.67 CTCs/mL. The patient died at day 538. (Bottom) In Patient P16, tumor burden decreased over time and was stable at the last time point. CTC number varied from 0.62 to 3.87 CTCs/mL but always with a high proportion of the CTCs being PD-L1 positive (between 80.6% and 100%).