The impact of irradiation dose on the computed tomography radiographic response of metastatic nodes and clinical outcomes in cervix cancer in a low-resource setting.

ABSTRACT

INTRODUCTION: The aim of this study is to investigate the relationship between the radiation dose to pelvic and para-aortic lymph nodes, nodal response, and clinical outcomes in a resource-poor setting based on computed tomography (CT) nodal size alone. MATERIALS AND METHODS: This retrospective study from 2009 to 2015 included 46 cervical cancer patients with 133 metastatic pelvic and para-aortic lymph nodes definitively treated with chemoradiation and brachytherapy in a public hospital with limited access to positron emission tomography (PET) scans. Hence, short axis of the lymph node on CT scan was used as a measure of metastatic nodal disease, before and following radiation therapy. Inclusion criteria required the pelvic and para-aortic nodes to have the shortest axis diameter on CT scan of ≥8 mm and ≥10 mm, respectively. Based on PET resolution, a node that decreased to half of its inclusion cutoff size was considered to have a complete response (CR). Relevant clinical outcomes were documented and correlated with nodal features, nodal radiation doses, and treatment characteristics. RESULTS: After controlling for other predictive factors, increased nodal dose was associated with increased probability of CR per study definition (P = 0.005). However, there was no statistically significant association between dose and pelvic/para-aortic, distant and total recurrence (TR), and any recurrence at any location (P = 0.263, 0.785, 1.00, respectively). Patients who had no CR nodes had shorter pelvic/para-aortic recurrence-free survival (PPRFS) and TR-free survival (TRFS) than patients who had at least one CR node (P = 0.027 and 0.046, respectively). Patients with no CR nodes also had shorter PPRFS than patients who had all nodes completely respond (P < 0.05). CONCLUSIONS: Using CT-based measures, we found that increased nodal dose is associated with an increased probability of CR (as defined) and nodal CR is associated with increased PPRFS and TRFS. We were unable to determine the cutoff dose required for a CR.