The value of the Prognostic Nutritional Index (PNI) in predicting outcomes and guiding the treatment strategy of nasopharyngeal carcinoma (NPC) patients receiving intensity-modulated radiotherapy (IMRT) with or without chemotherapy.

PURPOSE: The purpose of this study was to investigate the significance of the Prognostic Nutritional Index (PNI) in predicting prognoses and guiding treatment choices of nasopharyngeal carcinoma (NPC) patients receiving intensity-modulated radiotherapy (IMRT). METHODS: The 539 patients with newly diagnosed non-metastatic NPC were retrospectively analysed. The PNI was calculated as 10 × serum albumin (g/dL) + 0.005 × total lymphocyte count (per mm3). All patients were split randomly into a training set and a testing set. Receiver operating characteristic (ROC) curves were used to identify the cut-off value of PNI and test its prognostic validity. Survival curves were calculated by Kaplan-Meier method, and differences were compared with log-rank test. RESULTS: The median follow-up time was 109.5 months. The 5-year locoregional recurrence-free survival (LRRFS), distant metastasis-free survival (DMFS), disease-specific survival (DSS) and overall survival (OS) of the whole cohort were 90.6, 85.8, 85.3 and 82.7%, respectively. The PNI cut-off value was 52.0 in the training set, which was significant in predicting DMFS, DSS and OS in the testing set. According to the PNI cut-off value, 220 patients of II-IVb stage treated by concurrent chemoradiotherapy (CCRT) were classified into PNI ≤ 52.0 and >52.0 groups and the 5-year LRRFS, DMFS, DSS, and OS of PNI ≤ 52.0 group were significantly worse than the PNI > 52.0 group. CONCLUSION: Our results suggest that the PNI is a reliable independent prognostic factor in NPC patients treated with IMRT. For stage II-IVb patients with PNI ≤ 52.0, CCRT alone does not achieve satisfactory outcomes, and further studies on treatment optimization are needed.

[Application of amorphous silicon electronic portal imaging device (a-Si EPID) to dosimetry quality assurance of radiation therapy].

BACKGROUND & OBJECTIVE: Due to its good dosimetric properties, amorphous silicon electronic portal imaging device (a-Si EPID), as a rapid two-dimensional dosimetric measurement device, presents an attractive prospect in routine quality assurance (QA) test, dosimetric verification of intensity-modulated radiotherapy treatment (IMRT) and in vivo dose monitoring. This study was to explore the application of a-Si EPID as a detector for dosimetric QA of linear accelerator radiotherapy, and setup the calibration module. METHODS: The imaging calibration procedure of conventional a-Si EPID was modified for dosimetric measurement by acquiring the traditional "flush field" from integrated subfields to correct the dosimetric responding difference in pixel sensitivity. The energy dependence of the a-Si EPID detectors was analyzed through off-axis dose response curves. Calibrated dose profile obtained with a-Si EPID was compared with the measuring results of ion chamber in a 3-D water phantom. RESULTS: The calibrated dose profiles measured with a-Si EPID showed a deviation within 2% in high dose regions, but dropped much steeply in the penumbra region, as compared with that scanned using ion chamber in water. CONCLUSION: With the modeling management set up in this research, a-Si EPID can be applied for dosimetric QA of linear accelerator in radiotherapy.