Radiation-induced acute immediate nuclear abnormalities in oral cancer cells: serial cytologic evaluation

To evaluate the dose-response relationship of nuclear abnormalities in tumor cells collected by serial scrape smears from oral cancer patients on fractionated radiotherapy.

The study included 31 patients with squamous cell carcinoma of the oral cavity treated by radiotherapy (60 Gy in 25 fractions; 2.4 Gy per fraction). Serial scrape smears were taken from each tumor before treatment and after delivery of various fractions, usually 2 (4.8 Gy), 5 (12.0 Gy), 8 (19.2 Gy) or 12 (28.8 Gy). The smears were stained by Giemsa stain and evaluated by light microscopy, and the number of micronucleated, binucleated, nuclear budded and multinucleated cells were scored. Their relation to cumulative dose was analyzed by Kruskal-Wallis one-way analysis of variance. The results were expressed in terms of 1,000 mononucleated cells.

Even before treatment, most of the tumors showed various abnormally nucleated cells, and, despite the high intertumoral variation (as indicated by the high variance), all of them showed statistically significant dose-related increases. The mean values before treatment and after irradiation with 28.8 Gy, respectively, were 2.8 and 19.5 (P < .0001) for micronucleated cells, 1.5 and 8.5 (P < .000001) for nuclear budded cells, 8.2 and 35.5 (P < .0001) for binucleated cells, and 3.7 and 16.8 (P < .0001) for multinucleated cells. When the different types of nuclear abnormalities were combined and analyzed as "abnormally nucleated cells," the mean count before treatment and after 28.8 Gy were 7.9 and 44.9 (P < .00001), respectively.

The study showed that radiation-induced micronucleation, multinucleation, binucleation and nuclear budding in oral cancer cells has statistically significant dose-related increases that become evident in the initial few days of radiotherapy and that they can be differentiated well by cytology. This dose-response relationship and the high intertumoral variations suggest that serial assay of these changes has potential use for radiosensitivity prediction.