The first nationwide study of severe immune-related adverse events among cancer patients treated with immune checkpoint inhibitors helps identify those at elevated risk. The findingsat the Society for Immunotherapy of Cancer’s 35th Anniversary Annual Meeting.
“Immune-related adverse events are a very serious side effect of immune checkpoint inhibitor therapy, and as this therapy has become more common for treating advanced cancers, the incidence of immune-related adverse events has increased as well,” said presenting authora dual MD and MBA student at Harvard Medical School and Harvard Business School, both in Boston.
“However, because there is no ICD code for immune-related adverse events, it’s very difficult to study them at a population level. Most of the current literature around the incidence of immune-related adverse events and factors that are predictive of incidence are based on clinical trials and small studies,” Mr. Murphy noted.
He and his colleagues analyzed claims data from a U.S. nationwide health insurance plan for 14,378 patients who had a primary cancer and received at least one administration of an immune checkpoint inhibitor – an inhibitor of PD-1, PD-L1, or CTLA4 – during 2011-2019.
Over 19,117 patient-years of follow-up, 504 patients (3.5%) developed a severe immune-related adverse event (irAE), defined as one occurring within 2 years of their treatment and requiring inpatient hospitalization and new immunosuppression.
The incidence of severe irAEs per patient treatment year was 2.6% overall, rising from 0% in 2011 to 3.7% in 2016.
In multivariate analysis, patients had an elevated risk of severe irAEs if they received combination immunotherapy as compared with monotherapy (odds ratio, 2.44; P < .001).
On the other hand, risk fell with advancing age (OR, 0.98 per additional year; P < .001). And risk was lower for patients with melanoma (OR, 0.70; P = .01), renal cell carcinoma (OR, 0.71; P = .03), and other cancers (OR, 0.50; P < .001), compared with lung cancer.
Sex, geographic region, income, employment status, and comorbidity were not significantly associated with the risk of severe irAEs.
“We hope that patients and providers can use this evidence from a nationwide study of severe irAEs to guide treatment and management decisions,” Mr. Murphy concluded.
“As the use of immune checkpoint inhibitors increases for patients with a variety of different tumor types, there is increasing need for population-level evidence for patients treated outside of clinical trials,” said, an assistant attending physician with the melanoma service at Memorial Sloan Kettering Cancer Center in New York.
“This is a well-conducted study with an innovative approach to using real-world evidence to examine immune-related adverse events,” she added.
To her knowledge, it is the first study to look at multiple cancers for which immunotherapy is approved, Dr. Betof Warner said. This approach resulted in a large patient sample, giving power to detect differences between groups.
“The authors’ finding that combination immunotherapy is associated with more severe irAEs is in line with our clinical experience and other data sets, and the data regarding increased odds of severe irAEs in younger patients and those with lung cancer raise interesting biological questions about the etiology of irAEs,” Dr. Betof Warner noted.
However, certain factors complicate interpretation of the study’s findings, she cautioned. One such factor is requiring hospitalization to define an irAE.
“Practice patterns regarding hospitalization vary quite widely from center to center. For example, in some centers, all patients with immune-mediated colitis are hospitalized, whereas in others, these patients are managed predominantly in the outpatient setting, even in cases of high-grade toxicity,” she explained. “Practice patterns have also changed drastically over time as oncologists have grown more comfortable managing immune-related adverse events.”
Another factor is potential confounding. For example, patients with melanoma are more likely to receive combination immunotherapy given its longstanding approval for this cancer, whereas it is comparatively new for other cancers. Also, age may differ across cancers.
“The data the authors have provided are a great starting point, but I think further analysis is needed before these observations can be validated and integrated into practice,” Dr. Betof Warner concluded.
This study did not receive any specific funding. Mr. Murphy and Dr. Betof Warner disclosed no relevant conflicts of interest.
SOURCE: Murphy W et al. SITC 2020, .