Extended Data Table 6.

Adverse events leading to death in the as-treated population

	Pembrolizumab group (N-217)			Placebo group (N=216)
Event — no. (%)	Any cause	Treatment related*	Immune mediated†	Any cause	Treatment related*	Immune mediated†
Pneumonitis	2 (0.9)	1 (0.5)	2 (0.9)	0	0	0
Abdominal infection	1 (0.5)	0	0	0	0	0
Hepatitis	1 (0.5)	1 (0.5)	1 (0.5)	0	0	0
Multiple organ dysfunction syndrome	1 (0.5)	0	0	1 (0.5)	0	0
Myocardial infarction	1 (0.5)	0	0	0	0	0
Pneumonia	1 (0.5)	0	0	1 (0.5)	0	0
Aspiration	0	0	0	1 (0.5)	0	0
Cholangitis	0	0	0	1 (0.5)	1 (0.5)	0
Completed suicide	0	0	0	1 (0.5)	0	0
Craniocerebral injury	0	0	0	1 (0.5)	0	0
Death	0	0	0	1 (0.5)	0	0
Gastric cancer	0	0	0	1 (0.5)	0	0
Myocarditis	0	0	0	1 (0.5)‡	1 (0.5)‡	1 (0.5)‡
Respiratory tract infection	0	0	0	1 (0.5)	0	0

^*As indicated by the investigator.

^†Adverse events with a possible immune-mediated cause were considered regardless of attribution to study treatment by the investigator. The specific events are based on a list of terms provided by the sponsor. In addition to the specific terms listed, related terms were also included.

^‡Diagnosis of myocarditis was supported by post-mortem histological findings of a CD3-positive T cell population in the lymphocytic infiltrate in the myocardium; there were no features of myocardial infarction.