Image-guided adaptive brachytherapy in cervical cancer: Patterns of relapse by brachytherapy planning parameters

PURPOSE: Cervical cancer patients with a bulky high-risk clinical target volume (HR-CTV) get the largest benefit of dose escalation in terms of local control. However, the expected survival benefit could be lessened by a higher metastatic risk. We examined the patterns of relapse according to major prognostic factors: the HR-CTV volume and to the D-90 HR-CTV. METHODS AND MATERIALS: The clinical records of patients treated with pulsed-dose-rate image-guided adaptive brachytherapy after concurrent pelvic chemoradiation were reviewed. All patients had an optimal workup before treatment comprising a 18-fluorodeoxyglucose positron emission tomography/computed tomography and a para-aortic lymph node dissection. Patients with initial extrapelvic disease were excluded. RESULTS: A total of 109 patients fulfilled inclusion criteria. Median followup was 39 months. An HR-CTV volume >= 40 cm(3) was associated with a poorer local failure-free survival. There was a strong inverse correlation between the HR-CTV volume and the D-90 of the HR-CTV (correlation coefficient r = -0.696; p < 0.001) with increasing HR-CTV volume being associated with a decreasing D-90 HR-CTV. A D-90 HR-CTV <85 Gy and an HR-CTV volume >= 40 cm(3) were significant univariate factors for experiencing nonlocal failure (p = 0.002 and 0.035, respectively), even after exclusion of local relapses. CONCLUSION: A lower ability to reach the target D-90 HR-CTV planning and an HR-CTV volume > 40 cm(3) correlated with a high propensity of relapsing at distance, these factors being interrelated. Next step of treatment personalization should design strategies integrating this risk, which is now the main cause of failure. (C) 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.