The main purpose of this study is to evaluate the feasibility of a scalable, prospective research program for participants with metastatic non-small cell lung cancer (mNSCLC) or extensive-stage small-cell lung cancer (ES-SCLC) planning to start standard-of-care (SOC) systemic anti-cancer treatment. The study will also examine ctDNA status over the course of treatment as a predictor of response to therapy.

Inclusion Criteria:

• Documented diagnosis of mNSCLC or ES-SCLC
• Planned initiation of SOC systemic anti-cancer treatment
• Front-Line Immunotherapy Cohort: Received front-line treatment of an immune blockade therapy including anti-CTLA-4, anti-PD-1, or anti-PD-L1 therapeutic antibody on Protocol GX41563

Exclusion Criteria:

- Participant actively receiving investigational medicinal product(s) as part of an interventional trial at the time of signing informed consent

Qualified researchers may request access to individual patient level data through the clinical study data request platform (www.vivli.org). Further details on Roche's criteria for eligible studies are available here (https://vivli.org/ourmember/roche/). For further details on Roche's Global Policy on the Sharing of Clinical Information and how to request access to related clinical study documents, see here (https://www.roche.com/research\_and\_development/who\_we\_are\_how\_we\_work/clinical\_trials/our\_commitment\_to\_data\_sharing.htm).