Immunocytochemical detection of occult tumor cells in the bone marrow: prognostic impact on early stages of lung cancer

Objectives: This study was designed to verify the prognostic impact of occult tumor cells in the bone marrow of stage I and II non-small-cell lung cancer patients using cytokeratin as a micrometastatic marker. Methods: One hundred and fifty-two patients with stage I and II non-small-cell lung cancer, who underwent radical surgery by pulmonary lobectomy, were entered into the study. Bone marrow from fragments of resected ribs, and primary tumors were stained by anti-cytokeratin 18 antibody. Fourteen bone marrow specimens from patients without malignancy were used as a control group. Cancer recurrence was the study end point. Results: All the primary tumors were positive for cytokeratin; occult tumor cells were detected in 38 bone marrow specimens (25%). The prevalence of the occult tumor cells was not related to age, gender, tumor stage, histological differentiation or grade. The mean follow-up time was 35.3 months; 68 patients developed recurrence; the mean time for recurrence was 21.2 months. The general disease-free interval was not related to the presence of occult tumor cells in the bone marrow. This result did not change when grouping the patients by tumor stage. The stage was the best predictor of cancer recurrence (Cox proportional hazards model ratio: 2.09; p = 0.0026). Conclusions: This study confirms that immunocytochemical analysis detects occult tumor cells in the bone marrow of at least 25% of patients surgically treated for stage I and II non-small-cell lung cancer. These occult tumor cells do not have any impact on the disease-free interval. Copyright