This is an open label, single-center, non-randomized clinical trial on utilization of microbiome as biomarkers and therapeutics in immuno-oncology.

This research consists of two parts:

part 1: development of microbiome biomarkers for immuno-oncology part 2: proof-of-concept trial on the fecal microbiota transplantation in patients who are being treated with immunotherapy for advanced solid tumor

Part 1: development of microbiome biomarkers

<Inclusion Criteria:> 1.Patients with pathologically confirmed solid cancer who are being treated with immunotherapy or are going to receive immunotherapy

1. Age ≥ 19 years old
2. Eastern Cooperative Oncology Group performance status 0-2
3. Measurable or evaluable lesion(s) according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1

<Exclusion Criteria>

1. A history of other cancers requiring treatment within the recent 3 years (excepting treated basal or squamous cell carcinoma of the skin, superficial bladder cancer, or carcinoma in situ of the prostate, cervix, breast, or stomach)

2. A history of active primary immunodeficiency

3. Active infection including tuberculosis or Human Immunodeficiency Virus (HIV)

4. Autoimmune disease (excepting type 1 diabetes mellitus, hypothyroidism requiring hormone replacement therapy only, skin disease not requiring systemic therapy (such as vitiligo, psoriasis or alopecia)

5. Patients who are receiving immunosuppressive medications (excepting topical steroids, systemic steroid ≤10 mg/day prednisone or equivalents, or a brief course of steroids for prophylaxis (e.g., hypersensitivity reaction)

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part 2: proof-of-concept trial on the fecal microbiota transplantation in patients who are being treated with immunotherapy for solid cancers

<Inclusion Criteria for donors>

1. Patients who have partial or complete response to immunotherapy at the time of stool donation
2. No history of exposure to HIV or hepatitis virus within the previous 12 months
3. No history of international travel within previous 6 months to areas of high risk of travelers' diarrhea
4. No current communicable disease
5. No household members with active gastrointestinal infection
6. No history of inflammatory bowel disease
7. No recent intake of potential allergenic foods that are known to cause hypersensitivity in a recipient (such as peanut)

<Inclusion criteria for recipients>

1. Patients without contraindications for colonoscopy such as suspected bowel perforation, acute diverticulitis, or fulminant colitis
2. Patients who have disease progression to immunotherapy as one of the following two patterns:

2-1) Patients who have disease progression due to primary resistance to immunotherapy

2-2) Patients who have disease progression following disease stabilization due to secondary resistance to immunotherapy

IPD sharing is not planned.