Up to 25 percent of of lung cancer patients also have autoimmune disease, which may make them unsuitable for increasingly popular immunotherapy treatments.

Researchers calculated that between 14 to 25 percent of lung cancer patients reviewed also had immune disease, and these individuals were more likely to be female and older, according to the findings reported today in JAMA Oncology. 
An autoimmune disorder occurs when the immune system attacks and destroys healthy body tissue by mistake, according to The National Institutes of Health (NIH). There are more than 80 types of autoimmune disorders. The National Cancer Institute (NCI) estimates that approximately 39.6 percent of men and women will be diagnosed with cancer of any site at some point during their lifetime.

The results are significant because the use of immunotherapy for cancer treatment is expanding, and clinical trials of immunotherapy have routinely excluded patients with autoimmune disease, a population estimated to be between 20 to 50 million people in the U.S., said first author Dr. Saad Khan, Assistant Professor of Internal Medicine in the Division of Hematology and Oncology at UT Southwestern Medical Center's Harold C. Simmons Comprehensive Cancer Center. 

 "Our team wanted to determine if this practice had a significant impact. The new immunotherapy treatments also convey the risk of unpredictable, possibly severe, and potentially irreversible autoimmune toxicities affecting a variety of organs. With combination immunotherapy regimens, rates of these adverse events may exceed 50 percent," said Dr. Khan, a member of the Simmons Cancer Center.

"Our findings provide the first robust estimate of autoimmune conditions among lung cancer patients," said epidemiologist Dr. Sandi Pruitt, Assistant Professor in the Department of Clinical Sciences' Division of Outcomes and Health Services Research, and a member of the Simmons Cancer Center. "This study will influence clinical practice and the design of clinical trials, and raise additional research questions of critical importance to lung cancer patients and their doctors."

The researchers studied 210,509 lung cancer patients over age 65 and applied two different algorithms to measure the presence of an autoimmune disease. The most common autoimmune diseases reported were rheumatoid arthritis, psoriasis, and polymyalgia rheumatica. 

Potential explanations for the relatively high rate of autoimmune diseases among lung cancer patients include their advanced age at diagnosis and smoking history, which has been linked to risk of certain autoimmune diseases, Dr. Khan said.