Using the immune response to predict survival

This study examined complement activation as a new marker to predict prognosis among lung cancer patients.

Lung cancer screening methods, such as blood tests or imaging scans, can be helpful not only in diagnosing lung cancer, but also in predicting prognosis and response to treatment. The search for reliable predictors, often referred to as markers, has recently focused on markers of the immune response, and particularly the complement system. The complement system is a collection of proteins that help in the activation of certain immune responses. The complement system is thought to be over-activated in lung cancer, but its role is not yet fully understood. The current study examined the possibility of using measurements of complement system activation to predict the outcome of lung cancer patients.

In a lab investigation conducted on cells retrieved from lung cancer tumors, rapidly growing cancer cells were found to increase activation of the complement system. In an investigation of samples taken from 90 random lung cancer patients, levels of C4d (a molecule used to measure complement system activity since it is deposed in the tissue after activation) were found to correlate with overall survival. Even after adjusting for tumor stage and overall health status, high levels of C4d deposition tripled the risk of experiencing early mortality.

Among 83 advanced lung cancer patients, high levels of C4d in the blood (higher than 3 μg/mL) were significantly related to worse survival. Patients with higher C4d blood levels experienced a 59% increase in the risk of mortality compared to patients with lower C4d blood levels.

Blood C4d levels were also measured among 84 early stage lung cancer patients, and compared to those of 45 control patients (individuals with the same basic characteristics but without lung cancer). Significantly higher levels of C4d were seen among lung cancer patients compared to the control group. High levels of C4d were shown to be of significant prognostic value among early stage lung cancer patients. The risk of poor overall survival was 5-times higher among early stage lung cancer patients with C4d blood levels greater than 3 μg/mL.

This study concluded that complement system activation is significantly increased in lung cancer patients and may act as a predictor of survival.

Only a small number of patients were included in this study, and larger trials are needed to verify and further quantify these results.