IMPACT OF RADIATION-THERAPY FRACTION SIZE ON LOCAL-CONTROL OF EARLY GLOTTIC CARCINOMA

Purpose: Different radiotherapy fractionation schedules were used over a 10-year period to treat patients with early squamous cell carcinoma of the vocal cords at McGill University, A retrospective analysis was performed to study the effect of fraction size on local control in th is group of patients. Methods and Materials: A total of 126 previously untreated patients with T1 invasive squamous fell carcinoma of the tr ue vocal cords were irradiated between January 1978 and December 1988 in the Department of Radiation Oncology at McGill University, All pati ents received megavoltage irradiation, 94 patients received daily frac tions > 2 Gy (64 patients received 50 Gy with once-daily 2,5-Gy fracti ons, and 30 received 65.25 Gy in 29 fractions of 2.25 Gy each), and 32 patients were treated to a dose of 66 Gy in 33 fractions with 2 Gy/fr action, Patients' characteristics of prognostic importance were equall y distributed between the two fractionation groups. Results: At a medi an follow-up of 84 months, the 10-year disease-free survival and overa ll survival were 76% and 93%, respectively, Local control for patients treated with > 2 Gy fraction was 84%, compared to 65.6% for those tre ated with 2-Gy fractions (p = 0.026), Among the prognostic factors tes ted, such as gender, age, stage, anterior and posterior commissure inv olvement, smoking history, and fraction size, the latter was the only significant predictor of local control for the whole group of patients in univariate (p = 0.041) and multivariate (p = 0.023) analysis, Ther e was no observed difference in the incidence of complications between the two fractionation groups. Conclusions: From the results of this r etrospective review of patients treated with radiotherapy for T1 true vocal cord cancer, and within the range of total doses and overall tre atment times used in our patients, it was found that fractionation sch edules using daily fraction size > 2 Gy are associated with a better l ocal control than schedules delivering 2 Gy/fraction, with no increase in toxicity, (C) 1997 Elsevier Science Inc.