First clinical results of adaptive radiotherapy based on 3D portal dosimetry for lung cancer patients with atelectasis treated with volumetric-modulated arc therapy (VMAT).

UNLABELLED: Atelectasis in lung cancer patients can change rapidly during a treatment course, which may displace the tumor/healthy tissues, or change tissue densities locally. This may result in differences between the planned and the actually delivered dose. With complex delivery techniques treatment verification is essential and inter-fractional adaptation may be necessary. We present the first clinical results of treatment adaptation based on an in-house developed three-dimensional (3D) portal dose measurement (PDM) system. MATERIAL AND METHODS: A method was developed for 3D PDM combined with cone beam computed tomography (kV-CBCT) imaging. Lung cancer patients are monitored routinely with this imaging technique. During treatment, the first three fractions are analyzed with 3D PDM and weekly thereafter. The reconstructed measured dose is compared to the planned dose using dose-volume histograms and a γ evaluation. Patients having |γ|> 1 in more than 5% of the (primary tumor or organ at risk) volume were subjected to further analysis. In this study we show the PDM dose changes for five patients. RESULTS: We detected relevant dose changes induced by changes in atelectasis in the presented cases. Two patients received two treatment adaptations after being detected with PDM confirmed by visual inspection of the kV-CBCTs, and in two other patients the radiation treatment plan was adapted once. In one case no dose delivery change was detected with PDM. CONCLUSION: The first clinical patients show that 3D PDM combined with kV-CBCT is a valuable quality assurance tool for detecting anatomical alterations and their dosimetric consequences during the course of radiotherapy. In our clinic, 3D PDM is fully automated for ease and speed of the procedure, and for minimization of human error. The technique is able to flag patients with suspected dose discrepancies for potential adaptation of the treatment plan.

Development and validation of a nomogram for prediction of survival and local control in laryngeal carcinoma patients treated with radiotherapy alone: a cohort study based on 994 patients.

INTRODUCTION: To advise laryngeal carcinoma patients on the most appropriate form of treatment, a tool to predict survival and local control is needed. MATERIALS AND METHODS: We performed a population-based cohort study on 994 laryngeal carcinoma patients, treated with RT from 1977 until 2008. Two nomograms were developed and validated. Performance of the models is expressed as the Area Under the Curve (AUC). RESULTS: Unfavorable prognostic factors for overall survival were low hemoglobin level, male sex, high T-status, nodal involvement, older age, lower EQD(2T) (total radiation dose corrected for fraction dose and overall treatment time), and non-glottic tumor. All factors except tumor location were prognostic for local control. The AUCs were 0.73 for overall survival and 0.67 for local control. External validation of the survival model yielded AUCs of 0.68, 0.74, 0.76 and 0.71 for the Leuven (n=109), the VU Amsterdam (n=178), the Manchester (n=403) and the NKI cohort (n=205), respectively, while the validation procedure for the local control model resulted in AUCs of 0.70, 0.71, 0.72 and 0.62. The resulting nomograms were made available on the website www.predictcancer.org. CONCLUSIONS: For patients with a laryngeal carcinoma treated with RT alone, we have developed visual, easy-to-use nomograms for the prediction of overall survival and primary local control. These models have been successfully validated in four external centers.