Late Effects After Radiotherapy for Locally Advanced Cervical Cancer: Comparison of Two Brachytherapy Schedules and Effect of Dose Delivered Weekly

Purpose To compare the severe late effects (Grade 3 or greater) for two groups of cervical cancer patients treated with the same external beam radiotherapy and two high-dose-rate intracavitary brachytherapy regimens and to investigate the influence of the dose delivered each week. Methods and Materials For 120 patients, intracavitary brachytherapy was delivered with 33.6 Gy in eight fractions to Point A (HD group), and for 119, intracavitary brachytherapy was delivered with 29.4 Gy in seven fractions to Point A (LD group). The cumulative incidence of severe gastrointestinal and genitourinary late effects were calculated for both dose groups using Kaplan-Meier survival analysis. This method was also used to explore whether the number of weeks with different dose levels could predict the cumulative incidence of late effects. Results The actuarial rate of developing severe gastrointestinal morbidity at 7 years was 10.7% and 8.3% for HD and LD groups, respectively. The rate for genitourinary morbidity was 6.6% for the HD group and 5.0% for the LD group, respectively. No significant difference was found between the two groups. The analyses showed that a marginally significant increase occurred in severe gastrointestinal complications as the number of weeks with a physical dose >20 Gy increased in the HD group ( p = .047). Conclusion To establish dose–response relationships for late complications, three-dimensional imaging and dose–volume histogram parameters are needed. We found some indications that 20 Gy/wk is an upper tolerance level when the dose to the International Commission on Radiation Units and Measurements rectum point is 81 Gyα/β=3 (isoeffective [equivalent] dose of 2-Gy fractions). However, additional investigations using three-dimensional data are needed.