Hypofractionated radiotherapy for T1N0M0 glottic cancer: retrospective analysis of two different cohorts of dose-fractionation schedules from a single institution

AIMS

To determine the influence of dose and fractionation on tumour characteristics, toxicity, disease control and survival outcomes in T1 glottic carcinoma.

MATERIALS AND METHODS

Between 1975 and 2000, treatment charts of 652 patients with T1 glottic carcinoma who received curative radiation with four hypofractionated schedules (50 Gy/15 fractions [3.3 Gy/fraction] or 55 Gy/16 fractions [3.43 Gy/fraction] or 60 Gy/24 fractions or 62.5 Gy/25 fractions [2.5 Gy/fraction]) were analysed. The patients were divided into two groups based on fraction size <3 Gy and >3 Gy. Local control and overall survival were calculated. Patient- and tumour-related factors affecting local control were analysed using univariate and multivariate analysis. Factors affecting late toxicity were also analysed.

RESULTS

The local control and overall survival at 10 years were 84 and 86.1%, respectively, for T1 glottic carcinoma. The response to radiation had a significant effect on local control with univariate analysis (P = 0.001). Other factors, such as beam energy, anterior commissure involvement and fractionation, did not affect local control. Persistent radiation oedema was seen in 123 patients (23.4%) and was significantly worse in patients who received radiation with a larger field size (>36 cm(2)) on a telecobalt machine (P < 0.001).

CONCLUSIONS

Radical radiotherapy schedules incorporating a higher dose per fraction yield acceptable local control rates and late toxicity. Telecobalt therapy for early glottic cancer is a safe alternative to treatment with 6 MV photons on a linear accelerator in terms of local control and late toxicity as long as field sizes smaller than 36 cm(2) are used.