Evolution and Dosimetric Analysis of Magnetic Resonance Imaging-Detected Brain Stem Injury After Intensity Modulated Radiation Therapy in Nasopharyngeal Carcinoma.

PURPOSE: To evaluate the evolution of radiation-induced brain stem injury (BSI) in patients with nasopharyngeal carcinoma (NPC) treated with intensity modulated radiation therapy (IMRT) and to identify the critical dosimetric predictors of BSI. METHODS AND MATERIALS: A total of 6288 NPC patients treated with IMRT between 2009 and 2015 were retrospectively reviewed. Among these 6288 patients, 24 had radiation-induced BSI, which manifested as edematous lesions and contrast-enhanced lesions (CLs) on magnetic resonance imaging. Latency, symptoms, and evolution of BSI were assessed. Critical dosimetric predictors of BSI were identified using a penalized regression model with performance evaluated by receiver operating characteristic curve analysis. RESULTS: Median BSI latency was 14.5 months (range, 7.6-37.5 months), and 9 out of 24 patients (37.5%) were clinically symptomatic. Edematous lesions and CLs were both present in all patients. Necrosis was significantly more common in larger CLs (P = .007). After median follow-up of 12.5 months, 13 out of 24 patients (54.2%) had complete remission, and 5 out of 24 patients (20.8%) had partial remission. Remission was unaffected by whether or not symptomatic treatment was given. Maximum point dose (Dmax) was identified as the critical predictor of BSI (area under the receiver operating curve = 0.898), with the optimal cutoff equivalent dose in 2-Gy fractions (D2) being 67.4 Gy (sensitivity = 0.833, 20 out of 24; specificity = 0.835, 5234 out of 6264). Patients with Dmax ≥67.4 Gy (D2) were significantly more likely to develop BSI (odds ratio = 25.29; 95% CI, 8.63-74.14; P < .001) than those with Dmax <67.4 Gy (D2). CONCLUSIONS: In patients with NPC treated with IMRT, BSI generally tends to improve over time. Dmax = 67.4 Gy (D2) appears to be the dose constraint for brain stem, potentially providing clinicians with greater choice and flexibility when balancing the tumor target coverage and brain stem protection. Further studies are needed to validate our findings.

Incidence and dosimetric parameters for brainstem necrosis following intensity modulated radiation therapy in nasopharyngeal carcinoma.

OBJECTIVES: To clarify the incidence of brainstem toxicity and perform a dose-volume analysis for the brainstem after long-term follow-up of a large cohort of nasopharyngeal carcinoma (NPC) patients who underwent intensity-modulated radiation therapy (IMRT). MATERIALS AND METHODS: All patients with NPC treated with IMRT at Sun Yat-sen University Cancer Center between April 2009 and March 2012 were retrospectively reviewed. A total of 1544 patients with follow-up >12months and detailed treatment plan data were included. Radiotherapy was administered using the simultaneous integrated boost technique in 2.0-2.48Gy per fractions/28-33 fractions. Brainstem necrosis was defined as lesions with high signal intensity on T2-weighted images and low signal intensity on T1-weighted images, with or without enhancement after administration of contrast in follow-up MRI. RESULTS: After median follow-up of 79.7months (range, 12.2-85.6months), 2/1544 (0.13%) patients developed brainstem necrosis after intervals of 12.3 and 18.5months. Actuarial incidence of brainstem necrosis was 0.07%, 0.13%, 0.13% and 0.13% after 1, 2, 3 and 5years, respectively. Overall, 384 (24.9%), 153 (9.9%), 67 (4.3%), 39 (2.5%), 78 (5.1%), and 114 (7.4%) patients had excessive doses of Dmax≥64Gy, D1cc>59Gy, D2cc>59Gy, aV50>5.9cc, aV55>2.7cc and aV60>0.9cc respectively, of whom only two developed brainstem necrosis. CONCLUSIONS: Brainstem necrosis is rare in NPC. The definitive criteria based on conventional radiotherapy cannot accurately predict the occurrence of brainstem necrosis after IMRT, thus more flexible definitive criteria with strict restrictions need to be defined.

Induction Chemotherapy Has No Prognostic Value in Patients with Locoregionally Advanced Nasopharyngeal Carcinoma and Chronic Hepatitis B Infection in the IMRT Era.

BACKGROUND: The effectiveness of induction chemotherapy (IC) followed by concurrent chemoradiotherapy (CCRT) over CCRT alone in patients with locoregionally advanced nasopharyngeal carcinoma (NPC) and chronic hepatitis B infection in the intensity-modulated radiotherapy (IMRT) era is unknown. PATIENTS AND METHODS: A total of 249 patients with stage T1-2 N2-3 or T3-4 N1-3 NPC and chronic hepatitis B infection treated with IMRT were retrospectively reviewed. Propensity score matching (PSM) was employed to balance covariates; 140 patients were propensity-matched (1:1 basis). Survival outcomes in the IC+CCRT and CCRT groups were compared using the Kaplan-Meier method, log-rank test and Cox proportional hazards model. RESULTS: No significant survival differences were observed between IC+CCRT and CCRT (5-year overall survival, 88.3% vs. 82.2%; P=.484; disease-free survival, 73.9% vs. 75.2%; P=.643; distant metastasis-free survival, 84.1% vs. 85.1%; P=.781; and locoregional failure-free survival, 87.9% vs. 85.1%; P=.834). After adjusting for known prognostic factors in multivariate analysis, IC was not an independent prognostic factor for any outcome (all P>.05); subgroup analysis based on T category (T1-2/T3-4), N category (N0-1/N2-3), and overall stage (III/IV) confirmed these results. The incidence of hepatic function damage in the IC+CCRT and CCRT groups was not significantly different. CONCLUSION: IC+CCRT leads to comparable survival outcomes and hepatic function damage compared to CCRT alone in patients with locoregionally advanced NPC with chronic hepatitis B infection in the IMRT era. Further investigations are warranted.

Critical Evaluation of the Quality and Recommendations of Clinical Practice Guidelines for Nasopharyngeal Carcinoma.

Background: Given the distinct biological characteristics and regional distribution of nasopharyngeal carcinoma (NPC) compared with other head and neck cancers, and uncertainties regarding therapeutic strategies, physicians require high-quality clinical practice guidelines (CPGs) to provide transparent recommendations for NPC treatment. This study aimed to critically appraise the quality of NPC CPGs and assess the consistency of their recommendations. Methods: We identified CPGs that provided recommendations on the diagnosis and management of NPC published up to December 2015. Four investigators independently appraised CPG quality using the Appraisal of Guidelines for Research & Evaluation (AGREE) II instrument. Key recommendations by CPGs were also evaluated. Results: A total of 7 CPGs were eligible for this study: 5 produced by professional organizations or governmental agencies and 2 were developed based on expert consensus. Of the 6 AGREE II domains, the applicability domain scored consistently low across CPGs (range, 13.5%-30.2%); no CPG achieved a score of >50% in all 6 domains. The scope and purpose domain (≥73.6% for 4 CPGs) and editorial independence domain (≥75.0% for 6 CPGs) scored highest. Of the 23 AGREE II items, 9 scored less than half of the points available in all 7 CPGs. The recommendations by CPGs were consistent in general; heterogeneity mainly existed among recommended therapeutic strategies. Conclusions: Variation exists in NPC CPG development processes and recommendations. Increased efforts are required to make comprehensive resources available to guide healthcare providers and enhance delivery of high-quality, evidence-based care for NPC. International collaboration is necessary to enable the development of high-quality and regionally relevant CPGs for NPC.