High-dose-rate versus low-dose-rate brachytherapy in the treatment of cervical cancer: Analysis of tumor recurrence - The University of Wisconsin experience

Purpose: To retrospectively compare the clinical outcome for cervical cance r patients treated with high-dose-rate (HDR) vs. low-dose-rate (LDR) brachy therapy. Methods and Materials: One hundred ninety-one LDR patients were treated fro m 1977 to 1988 and compared to 173 HDR patients treated from 1989 to 1996. Patients of similar stage and tumor volumes were treated with identical ext ernal beam fractionation schedules. Brachytherapy was given in either 1 or 2 LDR implants for the earlier patient cohort, and 5 HDR implants for the l atter cohort. For both patient groups, Point A received a minimum total dos e of 80 Gy. The linear-quadratic formula was used to calculate the LDR dose -equivalent contribution to Point A for the HDR treatments. The primary end points assessed mere survival, pelvic control, relapse-free survival, and d istant metastases. Endpoints were estimated using the Kaplan-Meier method, Comparisons between treatment groups were performed using the log-rank test and Cox proportional hazards models. Results: The median follow-up was 65 months (2 to 208 months) in the LDR gr oup and 22 months (1 to 85 months) in the HDR group. For all stages combine d there was no difference in survival, pelvic control, relapse-free surviva l, or distant metastases between LDR and HDR patients. For Stage IB and PI HDR patients, the pelvic control rates were 85% and 80% with survival rates of 86% and 65% at 3 years, respectively. In the LDR group, Stage LB and II patients had 91% and 78% pelvic control rates, with 82% and 58% survival r ates at 3 years, respectively. No difference was seen in survival or pelvic control for bulky Stage I and II patients combined (> 5 cm). Pelvic contro l at 3 years was 44% (HDR) versus 75% (LDR) for Stage IIIB patients (p = 0. 002). This difference in pelvic control was associated with a lower surviva l rate in the Stage IIIB HDR versus LDR population (33% versus 58%,p = 0.00 4). The only major difference, with regard to patient characteristics, betw een the Stage IIIB patients was the incidence of hydronephrosis in the HDR vs. LDR group-28% vs. 12%, respectively (p = 0.05). For Stage IIIB patients treated with HDR, our analysis suggested that pelvic control rates improve d when the first brachytherapy insertion was performed after the majority o f external beam radiotherapy had been delivered. Conclusion: Similar outcome was observed for Stage IB and II patients treat ed with either HDR or LDR brachytherapy-regardless of tumor volume. However , poorer survival and pelvic control rates were observed for Stage IIIB pat ients treated with HDR brachytherapy. If HDR is used for Stage IIIB patient s, our results suggest the majority of external beam radiotherapy should be delivered prior to initiating the brachytherapy to allow for adequate tumo r regression. HDR brachytherapy is more convenient for patients, decreases the radiation exposure for health care workers, and should be considered a standard therapy for women with Stage I or II cervical cancer. (C) 1999 Els evier Science Inc.