Tumor dose-volume response in image-guided adaptive brachytherapy for cervical cancer: A meta-regression analysis

PURPOSE: Image-guided adaptive brachytherapy is a high precision technique that allows dose escalation and adaptation to tumor response. Two monocentric studies reported continuous dose-volume response relationships, however, burdened by large confidence intervals. The aim was to refine these estimations by performing a meta-regression analysis based on published series. METHODS AND MATERIALS: Eligibility was limited to series reporting dosimetric parameters according to the Groupe Europeen de Curietherapie-European SocieTy for Radiation Oncology recommendations. The local control rates reported at 2-3 years were confronted to the mean D-90 clinical target volume (CTV) in 2-Gy equivalent using the probit model. The impact of each series on the relationships was pondered according to the number of patients reported. RESULTS: An exhaustive literature search retrieved 13 series reporting on 1299 patients. D-90 high-risk CTV ranged from 70.9 to 93.1 Gy. The probit model showed a significant correlation between the D-90 and the probability of achieving local control (p < 0.0001). The D-90 associated to a 90% probability of achieving local control was 81.4 Gy (78.3-83.8 Gy). The planning aim of 90 Gy corresponded to a 95.0% probability (92.8-96.3%). For the intermediate-risk CTV, less data were available, with 873 patients from eight institutions. Reported mean D-90 intermediate-risk CTV ranged from 61.7 to 69.1 Gy. A significant dose-volume effect was observed (p = 0.009). The D-90 of 60 Gy was associated to a 79.4% (60.2-86.0%) local control probability. CONCLUSION: Based on published data from a high number of patients, significant-dose-volume effect relationships were confirmed and refined between the D-90 of both CTV and the probability of achieving local control. Further studies based on individual data are required to develop nomograms including nondosimetric prognostic criteria. (C) 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights