INTERNATIONAL JOURNAL OF ONCOLOGY 5: 117-121, 1994 Flow cytometric analysis in tumor and lymph node metastases of resected lung cancer E.C.M. BOLLEN 1 , B.SCHUTTE 2 , G.P.M. TEN VELDE 3 , F.C.S. RAMAEKERS 2 and G.H. BLIJHAM 4 Department of Surgery, De Wever Hospital, Heerlen; Departments of Molecular Cell Biology and Pulmonary Diseases, University of Limburg, Maastricht; Department of Oncology, University Hospital Utrecht, The Netherlands Received April 6, 1994; Accepted May 12, 1994 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJI Abstract. It has been suggested that a combined analysis of DNA ploidy of the primary tumor and of mediastinal lymph node metastases (LNM) in non-small cell lung cancer (NSCLC) is of prognostic significance in patients with N2- disease, implying that DNA ploidy can contribute towards the selection of patients for operation after a positive mediastinoscopy. To re-evaluate this, DNA flow cytometry was performed in paraffin-embedded material from 117 patients who underwent a complete resection with thorough mediastinal exploration. Flow cytometry was also performed in 54 LNM from 26 patients with N2 disease. The results of flow cytometry were correlated with clinicopathological characteristics and outcome and the data were analysed with the Cox regression model. No correlation was found between DNA ploidy and the survival of 117 patients. The outcome of 10 patients with N2 disease but only diploid LNM was not significantly different compared to that of the 16 patients with N2 disease and aneuploid LNM. When 3 or more LNM were analysed ploidy status was concordant with the ploidy of the primary tumor in 80% of the patients. A pneumonectomy, non-squamous cell carcinoma and Nl and N2 descriptors appeared to be unfavorable prognostic factors in the Cox regression model. It is concluded that combining the results of DNA ploidy in paraffin-embedded tissue from the primary tumor and from the LNM does not discriminate between patients of different prognostic subgroups and therefore most likely will not contribute towards the selection of patients for thoracotomy after a positive mediastinoscopy. Introduction A positive mediastinoscopy is a reason for excluding patients with non-small cell lung cancer from operation (1) but the question whether there is nevertheless a subgroup of patients in whom resection improves the outcome of zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Correspondence to: Dr E.C.M. Bollen, Department of Surgery, De Wever Hospital, PO Box 4446, 6401 CX Heerlen, The Netherlands Key words: non-small cell lung cancer, lymph node metastasis, flow cytometric analysis, N2-disease mediastinoscopically diagnosed N2 disease still has to be answered. It has been suggested that a thoracotomy may be worthwhile if tumor spread is intranodal in the involved lymph nodes obtained by mediastinoscopy (2). We have demonstrated, however, that it is seldom possible to differentiate intranodal from extranodal growth histologically in tissue obtained by mediastinoscopy because the lymph nodes are damaged by biopsy (manuscript submitted). Recently it has been suggested that the simultaneous determination of DNA-ploidy of the primary tumor and of the lymph node metastases (LNM) permits accurate prognostic evaluation in patients with a resected N2 disease (3). If this observation is reproducible, flow cytometric analysis of tissue obtained by bronchoscopic biopsy or transcutaneous needle aspiration in combination with flow cytometry analysis of lymph node metastases obtained by mediastinoscopy can provide useful information for selecting patients for thoracotomy. In the present study we analysed the DNA content of the primary tumors of 117 patients with non-small cell lung cancer. All patients had undergone extensive mediastinal exploration; in 26 of the 30 patients with N2 disease the involved mediastinal lymph nodes were analysed as well. Patients and methods Patient selection. Between January 1989 and August 1992, 149 consecutive patients underwent thoracotomy. All had undergone clinical staging including CT scan of the thorax. In case of mediastinal nodes exceeding 1 cm, a mediastinoscopy was performed especially for sampling the contralateral lymph nodes, which had to be negative for thoracotomy to be carried out. Thirty-two patients were excluded from the study. One patient was excluded because he had already been operated upon for brain metastasis and 8 patients because their lesions were not resectable. Twenty- three patients were excluded because they had not undergone mediastinal dissection. Therefore, 117 patients with a complete 'curative' resection and thorough exploration of the mediastinum remained for analysis. Patients' charts were reviewed and the following clinical and histological data were recorded: age, sex, weight loss 6 months before operation, date and type of operation, pathological TNM classification, course of the disease and, when applicable, date and cause of death. The median follow-up period was