T3N0 glottic carcinoma: DNA S-phase as a predictor of the outcome after radiotherapy

In consecutive series of 326 laryngeal cancer patients, of 29 (9%) with stage T3N0 glottic carcinomas, 23 achieved complete local remission after curative radiotherapy and form the basis of the present investigation. Flow cytometry determinations of DNA-ploidy status and the S-phase fraction, and a "histopathological malignancy grading system" were evaluated as possible patient- and/or tumor-related predictors of local recurrence. Twelve patients (52%) were continuously disease-free after radiotherapy, whereas 10 (43%) manifested local recurrence, and one distant metastasis. The radiotherapy delivered to patients who later suffered from a local recurrence did not differ from those being continuously disease-free. The frequency of local recurrence was significantly correlated to patients whose primary tumours manifested a low S-phase fraction (p < 0.05). A low S-phase fraction may indicate slowly proliferating tumour-cells, which become more radioresistant on exposure to a series of fractionated doses, as their reassortment into sensitive phases will be proportionately slower.