A Clinical-Radiomics Nomogram Based on Computed Tomography for Predicting Risk of Local Recurrence After Radiotherapy in Nasopharyngeal Carcinoma.

Purpose: We aimed to establish a nomogram model based on computed tomography (CT) imaging radiomic signature and clinical factors to predict the risk of local recurrence in nasopharyngeal carcinoma (NPC) after intensity-modulated radiotherapy (IMRT). Methods: This was a retrospective study consisting of 156 NPC patients treated with IMRT. Radiomics features were extracted from the gross tumor volume for nasopharynx (GTVnx) in pretreatment CT images for patients with or without local recurrence. Discriminative radiomics features were selected after t-test and the least absolute shrinkage and selection operator (LASSO) analysis. The most stable model was obtained to generate radiomics signature (Rad_Score) by using machine learning models including Logistic Regression, K-Nearest neighbor, Naive Bayes, Decision Tree, Stochastic Gradient Descent, Gradient Booting Tree and Linear Support Vector Classification. A nomogram for local recurrence was established based on Rad_Score and clinical factors. The predictive performance of nomogram was evaluated by discrimination ability and calibration ability. Decision Curve Analysis (DCA) was used to evaluate the clinical benefits of the multi-factor nomogram in predicting local recurrence after IMRT. Results: Local recurrence occurred in 42 patients. A total of 1,452 radiomics features were initially extracted and seven stable features finally selected after LASSO analysis were used for machine learning algorithm modeling to generate Rad_Score. The nomogram showed that the greater Rad_Score was associated with the higher risk of local recurrence. The concordance index, specificity and sensitivity in the training cohort were 0.931 (95%CI:0.8765-0.9856), 91.2 and 82.8%, respectively; whereas, in the validation cohort, they were 0.799 (95%CI: 0.6458-0.9515), 79.4, and 69.2%, respectively. Conclusion: The nomogram based on radiomics signature and clinical factors can predict the risk of local recurrence after IMRT in patients with NPC and provide evidence for early clinical intervention.

Interfractional and intrafractional errors assessed by daily cone-beam computed tomography in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy: a prospective study.

This prospective study was to assess interfractional and intrafractional errors and to estimate appropriate margins for planning target volume (PTV) by using daily cone-beam computed tomography (CBCT) guidance in nasopharyngeal carcinoma (NPC). Daily pretreatment and post-treatment CBCT scans were acquired separately after initial patient setup and after the completion of each treatment fraction in 10 patients treated with IMRT. Online corrections were made before treatment if any translational setup error was found. Interfractional and intrafractional errors were recorded in the right-left (RL), superior-inferior (SI) and anterior-posterior (AP) directions. For the translational shifts, interfractional errors >2 mm occurred in 21.7% of measurements in the RL direction, 12.7% in the SI direction and 34.1% in the AP direction, respectively. Online correction resulted in 100% of residual errors ≤2 mm in the RL and SI directions, and 95.5% of residual errors ≤2 mm in the AP direction. No residual errors >3 mm occurred in the three directions. For the rotational shifts, a significant reduction was found in the magnitudes of residual errors compared with those of interfractional errors. A margin of 4.9 mm, 4.0 mm and 6.3 mm was required in the RL, SI and AP directions, respectively, when daily CBCT scans were not performed. With daily CBCT, the margins were reduced to 1.2 mm in all directions. In conclusion, daily CBCT guidance is an effective modality to improve the accuracy of IMRT for NPC. The online correction could result in a 70-81% reduction in margin size.

Feasibility and efficacy study of weekly cisplatin with concurrent intensity-modulated radiation therapy for nasopharyngeal carcinoma: preliminary results.

The aim of this study was to assess the feasibility and efficacy of a weekly cisplatin 40 mg/m(2) regimen in patients with nasopharyngeal carcinoma treated concurrently with definitive intensity-modulated radiation therapy (IMRT). The primary endpoints were treatment compliance and acute toxicities. Twenty-two patients with newly diagnosed NPC were recruited in this phase II trial. All patients received definitive IMRT concurrently with weekly cisplatin 40 mg/m(2) for six cycles. The treatment technique was split-field IMRT (SF-IMRT) before August 2009 and whole-field IMRT (WF-IMRT) thereafter. The median follow-up time was 15.1 months (range, 1.5-30 months). No patients experienced regional recurrence or distant metastasis. One patient developed local recurrence. One patient died of non-malignant disease. For all patients, the 1-year overall survival, local recurrence-free survival, regional recurrence-free survival, and distant metastasis-free survival were 95.5%, 95.5%, 100%, and 100%, respectively. All patients received the full dose of RT. Twenty-one patients (95.5%) completed all six cycles of chemotherapy (CHT). Three patients experienced treatment delay. Of them, one had CHT delay, and the other two had IMRT delay. No treatment-related death was found. Acute toxicities were generally mild or moderate. Grade 3 and 4 toxicities accounted for less than 10% of overall occurrence in each corresponding category except for a relatively higher rate in stomatitis (Grade 3, 27%). Renal function impairment was not found. Weekly cisplatin with concurrent IMRT appears to be feasible and effective in treating NPC patients and these findings warrant further investigation.