Frequency and prognostic relevance of disseminated tumor cells in bone marrow of patients with metastatic renal cell carcinoma.

Background: The prognostic relevance of disseminated cytokeratin-positive (CK+) tumor cells in the bone marrow of patients with different types of carcinoma has been demonstrated in several studies. In this prospective study, the frequency and prognostic value of CK+ tumor cells was investigated in the bone marrow of 55 consecutive patients with metastatic renal cell carcinoma (M1 RCC) in comparison with 256 M0 RCC patients from a previous study.

Methods: Aspiration of bone marrow from the anterior iliac crest was performed immediately before tumor resection in RCC patients. Cytospins were made and stained by immunocytochemistry using the APAAP (alkaline phosphatase-antialkaline phosphatase) protocol and monoclonal antibodies CK2 and A45-B/B3. Twenty-seven patients with no evidence of any malignant disease served as a control group.

Results: CK+ tumor cells were detected in 42% (23 of 55 patients) of the M1 patients and 25% (63 of 256 patients) of the M0 patients (P <.01). No CK+ cells (0 of 27 patients) were detected in the control group. In the M1 group, CK- patients demonstrated a trend toward a better outcome compared with CK+ patients (log-rank test, P = .19). This difference was significant when applying a higher threshold (0-2 CK+ cells vs. > or = 3 CK+ cells; P <.05). On multivariate analysis, the detection of > or = 3 CK+ cells in the bone marrow was found to be an independent prognostic factor (P <.001).

Conclusions: The results of the current study indicate that disseminated CK+ cells play a role in the biology of tumor spread of RCC, and that their immunocytochemical detection can be useful in assessing the prognosis of patients with M1 disease.