This study is for older adults with colorectal cancer. The purpose is to determine if low muscle mass plays a role in side effects from chemotherapy.

This is a research study to compare the effects and safety, good or bad, of tislelizumab (also known as BGB-A317) plus chemotherapy against placebo (an inactive substance) plus chemotherapy for adults with locally advanced recurrent or metastatic esophageal squamous cell carcinoma to find out which is better. Subjects may continue study treatment during their participation in the study as long as there is no worsening of disease and they don't have intolerable side effects from the study treatment

This study is for patients that have been diagnosed with Merkle Cell Carcinoma. The investigational drug in this study is pembrolizumab. The purpose of this study is to compare the usual approach of post-surgery observation with or without radiation to using pembrolizumab with or without radiation after surgery. Participants can expect to be on this study for a total of 5 years.

This study is for patients that have been diagnosed with Merkel cell carcinoma. The investigational drug in this study is pembrolizumab. This study will compare any good and bad effects of using radiation along with an immunotherapy treatment [MK-3475 (pembrolizumab)] compared with MK-3475 (pembrolizumab) alone. Participants can expect to be in this study for up to 7 years.