Pembrolizumab in Treating Patients With Advanced Merkel Cell Cancer

Inclusion Criteria

• Patients must have biopsy-proven metastatic MCC or locoregional MCC that has recurred following standard locoregional therapy with surgery and/or radiation therapy
• Patients must have measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 assessed by computed tomography (CT) scan, or for skin lesions not measurable by CT scan, measurements may be performed with caliper or flexible ruler
• Note: stage IV no evidence of disease (NED) is excluded by this criterion
• Have a performance status of = = 2,000/mcL (labs should be performed within 14 days of treatment initiation)
• Absolute neutrophil count >= 1, 500/mcL (labs should be performed within 14 days of treatment initiation)
• Platelets >= 100, 000/mcL (labs should be performed within 14 days of treatment initiation)
• Hemoglobin >= 9 g/dL OR >= 5.6 mmol/L (labs should be performed within 14 days of treatment initiation)
• Serum total bilirubin = 1.5 x ULN (labs should be performed within 14 days of treatment initiation)
• Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase [SGOT]) and alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT]) = = 30 mL/min for subject with creatinine levels > 2.5 x institutional ULN
• Creatinine clearance should be calculated per institutional standard (labs should be performed within 14 days of treatment initiation)
• Thyroid stimulating hormone (TSH) within institutional limits (i.e.: normal); if TSH is greater or less than institutional limits patients may participate if their T4 is within normal limits (WNL); patients may be on a stable dose of replacement thyroid medication; dose adjustments are allowed if needed (labs should be performed within 14 days of treatment initiation)
• Patients must provide tissue from an archival tumor sample or newly obtained core, punch or excisional biopsy of a tumor lesion if deemed relatively safe and technically feasible
• Note: newly obtained biopsy is preferable
• Female patients of childbearing potential must have a negative urine or serum pregnancy within 72 hours before receiving the first dose of study medication; if the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required
• Note: women of child-bearing potential must agree to use 2 methods of birth control, or be surgically sterile, or abstain from heterosexual activity beginning with the screening visit and for the duration of study participation, through 120 days beyond last dose of MK-3475 administration; patients of childbearing potential are those who have not been surgically sterilized or have not been free from menses for > 1 year; should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately
• Men treated or enrolled on this protocol must agree to use 2 adequate methods of contraception starting with the screening visit, for the duration of study participation, and through 120 days after the last dose of MK-3475 administration
• Ability to understand and willingness to sign a written informed consent document

Exclusion Criteria

• Patient has had prior systemic therapy for MCC
• Note: prior systemic cytotoxic chemotherapy will be allowed if it was administered in the adjuvant setting (no clinically detectable MCC at the time) and treatment concluded more than 6 months prior to beginning study treatment
• Patient is currently participating in or has participated in a study of an investigational systemic agent to treat MCC; or is using an investigational device within 4 weeks of the first dose of treatment
• NOTE: if patient received major surgery, they must have recovered adequately from the toxicity and/or complications from the intervention prior to starting therapy
• Toxicity from surgery or associated interventions that has not recovered to = = 45 years of age and has not had menses for gre