Histologic Assessment of Tumor-Associated CD45+ Cell Numbers Is an Independent Predictor of Prognosis in Small Cell Lung CancerSmall Cell Lung Cancer: CD45+ Cells and Outcome

BACKGROUND: Small cell lung carcinoma (SCLC) continues to have poor prognosis with a 2 year survival of less than 20%. Recent studies have suggested that SCLC may affect the immune system to allow it to evade immunological responses. We hypothesised that any such effect would be characterised by a decrease in lymphoid cells associated with tumour in biopsies and that this might relate to patient outcome.
METHODS: Sixty-four SCLC biopsies were immunohistochemically stained with anti-CD45 antibody to identify immune cells associated with tumour. A mean CD45 count per high power field for each case was obtained and the results correlated with age, sex, stage, performance status (PS), treatment with chemotherapy / radiotherapy and overall survival.
RESULTS: The median CD45 count for all cases was taken as 40 (CD4540). Kaplan-Meier plots demonstrated better survival for patients with a CD4540 >40 (p<0.009). No relationship between CD4540 and age, sex , stage, treatment by chemotherapy or radiotherapy was identified. While PS was a significant predictor of survival (p=0.014) it did not correlate with CD4540. In patients with better ECOG performance status (PS ≤ 2) the CD4540 demonstrated a highly significant survival advantage for those with CD4540 >40 (p<0.0001).
CONCLUSIONS: The data indicate that a) simple immunohistochemical assessment of immune cell infiltrates in routinely processed and stained biopsies of primary tumours can provide prognostic information in SCLC; and, b) tumour associated CD45+ cells in SCLC biopsies may be a good clinical marker to identify patients with poor prognosis despite good PS.