Checkpoint blockade and microsatellite instability

A method for treating cancer in a patient in need thereof, the method comprising:

• detecting a high microsatellite instability (MSI-high) or a mismatch repair (MMR) deficiency status in a tumor sample from the patient;
• wherein the tumor sample exhibits an instability of one or more microsatellite markers or a deficiency of one or more mismatch repair markers;
• administering an effective amount of pembrolizumab to the patient;
• determining that the patient exhibits an outcome that is improved as compared to a corresponding outcome that would be observed in a reference patient that has been administered pembrolizumab, wherein reference patient has a tumor that does not exhibit an instability of the one or more microsatellite markers or a deficiency of the one or more mismatch repair markers;
• and
• wherein the patient has received a prior cancer therapy drug.

A method for treating cancer in a patient in need thereof comprising:

• selecting a patient who has an unresectable or metastatic, microsatellite instability-high (MSI-H) or mismatch repair (MMR) deficient solid tumor, the tumor having progressed following a cancer therapy;
• administering an effective amount of pembrolizumab to the patient;
• and
• determining that the patient exhibits an outcome that is improved as compared to a corresponding outcome that would be observed in a reference patient that has been administered pembrolizumab, wherein the reference patient has a tumor that does not exhibit a MSI-high or a MMR deficiency status.