Peripheral blood lymphocyte subsets and survival in small-cell lung cancer.

Measurement of lymphocyte subsets in peripheral blood is likely to reflect immune response of patients and therefore may be linked to survival in small-cell lung cancer (SCLC). Forty patients with SCLC (14 with limited and 26 with extensive disease at study entry) were included and followed for up to 23 months. Peripheral blood lymphocytes were determined by flow cytometry and levels for total-, T-, B-, helper-, suppressor-, activated T-cells and natural killer cells established and the T-helper-suppressor ratio (H-S ratio) calculated. Quartiles of lymphocyte subset cell counts at the start of follow-up and for the change over follow-up were investigated. Cox regression models indicated that H-S ratio was a significant predictor (p = 0.02) of survival. The risk ratio, after adjustment for competing risk factors, sex, age and stage of disease, was found to be 0.66 (95 percent confidence intervals, 0.46 to 0.95) and predicted that for each quartile of greater H-S ratio, the risk of death decreased by 34 percent. For change in cell counts over follow-up, total lymphocytes (p = 0.02) demonstrated a significant association with survival. Although our observation is limited by the fact that 13 patients were unavailable for follow-up, we conclude that H-S ratio can serve as an easily accessible marker of immune function and possible prognostic value in SCLC.