Tempus Sculptor Study: Small Cell Lung Cancer (SCLC) Observational Study

The following are the inclusion criteria. Participants are eligible to be included in this study only if all the following criteria apply. The participant has/is: * Histologically confirmed small cell lung cancer diagnosis * Diagnosis made with excisional or core needle biopsy specimen (fine needle aspirate may be permitted with approval from the PI) * Subjects must submit fresh or archived FFPE tumor sample to the central laboratory * ECOG performance status of 0-2 at time of enrollment * Planned extensive stage first-line therapy of etoposide plus carboplatin plus PD-L1 inhibitor (atezolizumab or durvalumab) * Extensive stage disease at time of diagnosis * Willing and able to provide informed consent * Radiotherapy is permitted as long as there is measurable disease outside of the radiotherapy port Participants will be excluded from the study if any of the following criteria apply. The participant has/is: * History of prior systemic treatment of SCLC * Prior diagnosis of non-small cell lung cancer is excluded if the cancer is diagnosed \< 3 years prior to study entry. Additionally, the participant must be off all therapy for the NSCLC at the time of study entry. * Mixed small cell and non-small cell histology * Suspected metastatic cancer from other sites (i.e., those without a known or suspected lung primary diagnosis) * Not willing to have additional blood samples collected