BACKGROUND For patients with non-small cell lung cancer the TNM staging system and other conventional prognostic factors fail to predict accurately the outcome of treatment and survival. This study attempts to determine the prognostic value for survival of the proportions of CD4+ lymphocytes in the pleural cavity (PLY) of patients with resectable non-small cell lung cancer.

RESULTS The 5 year survival rate of patients with percentage CD4+ PLY of ⩽30% was 84% whereas that of patients with %CD4+ PLY >30% was 26.9%. The difference in survival between the %CD4+ PLY ⩽30% and %CD4+ PLY >30% groups was significant (p<0.0001). The %CD4+ PLY in those who survived for 5 years was significantly lower than that in the patients who died within 5 years (p<0.0001). The difference in survival between patients with stage IA and IB lung cancer with %CD4+ PLY ⩽30% and those with %CD4+ PLY >30% was also significant (p =0.015). Multivariate analysis showed that the proportion of CD4+ PLY (hazard ratio=6.9, 95% CI 0.045 to 0.47) and nodal status (hazard ratio=22.7, 95% CI 0.006 to 1.806) are significant and independent prognostic factors for the survival of patients with lung cancer.

CONCLUSIONS The proportion of CD4+ PLY may help to select patients who are likely to have a poorer prognosis after surgery and therefore may be suitable for consideration of adjuvant treatments. These results need confirmation in a larger prospective study.