Comparative DNA analysis by image cytometry and flow cytometry in non-small cell lung cancer

To determine whether image cytometry (ICM) is advantageous for clinical DNA analyses of tumor cells, nuclear DNA contents measured by ICM were compared with those by flow cytometry (FCM), using 46 samples of non-small cell lung cancers. ICM was performed on smear specimens of fresh materials (f-ICM) and cell suspensions obtained from paraffin-embedded tumors (p-ICM). The same cell suspensions were also analyzed by FCM (p-FCM). Aneuploid rates/coefficient of variation (CV) of f-ICM, p-ICM, and p-FCM were 76.1/4.90, 71.7/5.01 and 60.9/5.31%, respectively. There was a high correlation in the DNA indices between p-ICM and p-FCM (r = 0.80). In the comparative DNA analysis, there were seven discordant samples. Six of them were estimated as aneuploid by p-ICM, but they were miscounted as diploid or undefinable (impossible) by p-FCM. This was caused by measuring condensed nuclei or debris. All "impossible" samples in p-FCM were squamous cell carcinoma with necrosis. In cell cycle analysis, the S and S+G2/M phase fractions in diploid samples were higher in p-ICM than those in p-FCM (P < 0.005), because the G0/G1 phase (2N) fraction presented by FCM was composed of cancer and non-malignant cells in diploid cancers. In ICM, they can be separately measured by means of morphological selection. These findings indicated that ICM is superior to FCM, especially for the practical DNA measurement of a few cancer cells and in the evaluation of the proliferation rates.