Use of Serial Plasma NGS as a New Efficacy Metric to Guide Immunotherapy Treatment Discontinuation

This is a prospective study using Simon's two stage design to investigate the use of ctDNA to guide end of therapy decisions. Approximately 39 patients with an established diagnosis of metastatic melanoma or NSCLC with evidence of disease control (SD, PR, or CR) will be enrolled in the study. Patients that sign a pre-screening consent will have archival tumor tissue sent to Foundation Medicine for generation of the F1CDx. Patients may begin screening after 10 months of an ICI containing regimen with plan to complete at least 1 year of systemic therapy. After successful generation of F1CDx whole blood will be collected and analyzed for plasma ctDNA measurement. Eligible patients for enrollment are ctDNA negative and have received at least 12 months but no more than 18moths of ICI. Eligible patients will be offered to consent to the main study and have standard of care imaging as well as blood draws for ctDNA assessment at screening, 1 month, 2 month, 3 months, 6 months, 9 months, and 12 month/end of study.