Exfoliative cytology in radiotherapy of oral cancer. Its use in the diagnosis of residual carcinoma.

Abstract

The exact biological status of an oral carcinoma is often difficult to assess on the completion of irradiation. Residual neoplasm may be suspected because of persistent induration, excrescence, or ulceration. The radiation reaction, usually intense at this time, makes interpretation of these findings uncertain. Immediate biopsy is not advisable and determination of cancer cell viability by histologic examination may be difficult. This paper reports a study undertaken to ascertain the value of oral smears in the diagnosis of residual neoplasm following irradiation for oral cancer. Material and Method Direct smears were taken from the sites of 25 irradiated oral carcinomas of the floor of the mouth, palate, gingiva, tongue, tonsil, and glossopalatine fold. The smears were obtained during and at the completion of treatment, which was usually administered over periods of five to seven weeks. In 14 of the cases smears were also taken during the post-irradiation months. The smears were fixed in ether-alcohol, stained according to the Papanicolaou technic, and examined for the presence of malignant cells, with no attempt at differentiation of viable from nonviable cells. Results The cytologic findings during irradiation have been published elsewhere (1­4). In 16 of the 25 patients malignant cells were still present in the smears at the completion of treatment; the smears from 5 others were equivocal, and in the remaining 4 the smears were negative (Table I). As shown in Table I, the presence or absence of residual neoplasm, clinically, had no effect on the cytologic findings in smears taken immediately following treatment. Negative and positive results occurred with equal frequency in each group. Cytologic examination two to ten weeks later showed no correlation with observations on completion of treatment, and more accurately reflected the clinical status (Table II). The 2 patients whose smears had been negative at the end of treatment, despite obvious residual neoplasm (Table I), now had smears which were positive for malignant cells. On the other hand, malignant cells disappeared from the smears of 5 of the 13 patients with no clinical evidence of residual neoplasm. Smears from 1 other patient were suspicious for malignant cells, and the remaining 7 patients either did not have the benefit of follow-up smears or were not evaluated cytologically until many months later. The following cases illustrate the type of information obtained by this form of cytologic study. Case I : An infiltrating, well differentiated squamous-cell carcinoma in the right lower gingivobuccal sulcus was given external and peroral x-irradiation. At the completion of treatment there remained only a small, granular irregularity, which was thought to represent granulation tissue. Smears taken at the completion of treatment and at monthly intervals thereafter, however, all contained malignant cells.