Grant: Project Grant

Background and Importance: Immunotherapy, which works by activating the immune system, has received a lot of interest due to its ability to improve cancer survival and even cure certain late-stage cancers. Over 40% of patients with cancer can be treated with immunotherapy. However, by activating the immune system, immunotherapy can cause unwanted side effects such as inflammatory arthritis (ICI-IA), which can cause severe joint pain. Little is known about who gets ICI-IA and what happens to them. Most studies on ICI-IA have only included small numbers of patients. One major barrier to studying ICI-IA in large groups of people is the lack of validated case definitions. Canada is in a unique position to conduct this study as the only country with a national database of rheumatologist-confirmed cases of ICI-IA (the CanRIO database). Research Aims: 1. Validate administrative data definitions of ICI-IA. 2. Evaluate ICI-IA in Canadians using health care administrative data. Methods: Aim 1: Using rheumatologist-confirmed cases of ICI-IA from the CanRIO database as the gold standard, we will test various administrative healthcare data case definitions based on physician billing codes, hospitalization codes, medication codes and lab test results. Aim 2: We will use the most accurate case definition from Aim 1 to find cases of ICI-IA in multiple provinces and study frequency of, risk factors associated with and outcomes after the development of ICI-IA. Expected Outcomes/Impacts: Our work will help us understand how common ICI-IA is in patients using immunotherapy for cancer. Patients and doctors will be able to make better informed decisions on the risk to benefit balance of immunotherapy. Our work will also help doctors identify those at highest risk for ICI-IA and start earlier screening and treatments to lessen or prevent long term consequences of ICI-IA.