The microbiome has the potential to serve as a robust biomarker of clinical response to immunotherapy. Additionally, microbial manipulation, through diet, exercise, prebiotics, probiotics, or microbially-derived metabolites, may prove to be beneficial in promoting anti-tumor immune responses. However, large prospective studies in humans with longitudinal sample collection and standardized methods are needed to understand how microbiota and their byproducts affect cancer therapies, particularly among patients undergoing identical therapy but experiencing different outcomes. The proposed observational study builds upon these hypotheses by proposing a large cohort design to further assess the associations between the gut microbiota (composition and function), host immune system, and ICI treatment efficacy across multiple cancer types.

Inclusion Criteria:

1. Men or women ≥18 years of age
2. Screened negative for COVID-19 symptoms at time of consent, as per institutional policy and as applicable for the duration of the COVID-19 pandemic
3. Diagnosed with stages I-IV primary NSCLC, MM, TNBC or RCC
4. Plan to be treated at a partner cancer site with a checkpoint inhibitor (anti-PD-1, anti-PD-L1, or anti-CTLA-4) as a single agent or in combination with another checkpoint inhibitor or other treatment agent or modality (e.g., targeted therapy, chemotherapy, surgery, radiation, etc.) in accordance with FDA-labeled use of the agent
5. Able to provide informed consent and answer study questionnaires in either English or Spanish
6. Able to provide stool specimens for research purposes

Exclusion Criteria:

1. Mental incapacity
2. Incarcerated individuals
3. Pregnancy (by self-report of pregnancy status)
4. Experiencing active brain metastasis/metastases
5. Treatment with checkpoint inhibitor in off-label capacity or through a clinical/interventional trial
6. Active participation in an immuno-oncology clinical/interventional trial or pharma-sponsored observational study

The investigator propose to enroll 800 cancer patients (NSCLC, MM, RCC, and TNBC; any stage) who are about to begin standard of care ICI therapy into a multi-site prospective observational study of the gut microbiome.