FOI reference: FOI-2025-3239
You asked
We are keen to identify the number of patients who have died as a direct result of immunotherapy treatment (specifically immune checkpoint inhibitor) adverse events as these are often not reported to the Medicines Health Regulatory Authority (MHRA).
I would be grateful if we could please enquire about whether these deaths are recorded with a specific cause of death code?
We said
Thank you for your request.
Our mortality data comes from the information collected at death registration. All of the conditions mentioned on the death certificate are coded using the International Classification of Diseases, Tenth Revision (ICD-10). From all of these causes an underlying cause of death is selected using ICD-10 coding rules.
The underlying cause of death is defined by WHO as:
a) the disease or injury that initiated the train of events directly leading to death, or
b) the circumstances of the accident or violence that produced the fatal injury
There is no ICD10 code that relates specifically to adverse reactions to immune checkpoint inhibitors. However, ICD10 code Y43.4 does identify deaths where there were complications due to the use of immunosuppressive agents.
For deaths registered between 2001 and 2025, there were 5,030 deaths where Y43.3 was mentioned on the death certificate. These figures are for persons resident in England and Wales.
National Records Scotland (NRS) and Northern Ireland Statistics and Research Agency (NISRA) are responsible for statistics pertaining to Scotland and Northern Ireland. They can be contacted at foi@nrscotland.gov.uk and info@nisra.gov.uk respectively.