Histologic Assessment of Tumor-Associated CD45+ Cell Numbers Is an Independent Predictor of Prognosis in Small Cell Lung Cancer

BackgroundSmall cell lung carcinoma (SCLC) continues to have a poor prognosis, with a 2-year survival of < 20%. Studies have suggested that SCLC may affect the immune system to allow it to evade immunologic responses. We hypothesized that any such effect would be characterized by a decrease in the lymphoid cells associated with the tumor in biopsy specimens and that this might relate to patient outcome.MethodsSixty-four SCLC biopsy specimens were immunohistochemically stained with anti-CD45 antibody to identify immune cells associated with the tumor. A mean CD45 count per high-power field for each case was obtained, and the results were correlated with age, sex, stage, performance status (PS), treatment with chemotherapy/radiotherapy, and overall survival.ResultsThe median CD45 count for all cases was taken as 40 (CD4540). Kaplan-Meier plots demonstrated better survival for patients with a CD4540 > 40 (P < .009). No relationship between CD4540 and age, sex, stage, or treatment by chemotherapy or radiotherapy was identified. Although PS was a significant predictor of survival (P = .014), it did not correlate with CD4540. In patients with better Eastern Cooperative Oncology Group PS (≤ 2), the CD4540 demonstrated a highly significant survival advantage for those with CD4540 > 40 (P < .0001).ConclusionsThe data indicate that (1) simple immunohistochemical assessment of immune cell infiltrates in routinely processed and stained biopsy specimens of primary tumors can provide prognostic information in SCLC and (2) tumor-associated CD45+ cells in SCLC biopsy specimens may be a good clinical marker to identify patients with poor prognosis despite good PS.