Evaluating contouring accuracy and dosimetry impact of current MRI-guided adaptive radiation therapy for brain metastases: a retrospective study.

BACKGROUND: Magnetic resonance imaging (MRI) guided adaptive radiotherapy (MRgART) has gained increasing attention, showing clinical advantages over conventional radiotherapy. However, there are concerns regarding online target delineation and modification accuracy. In our study, we aimed to investigate the accuracy of brain metastases (BMs) contouring and its impact on dosimetry in 1.5 T MRI-guided online adaptive fractionated stereotactic radiotherapy (FSRT). METHODS: Eighteen patients with 64 BMs were retrospectively evaluated. Pre-treatment 3.0 T MRI scans (gadolinium contrast-enhanced T1w, T1c) and initial 1.5 T MR-Linac scans (non-enhanced online-T1, T2, and FLAIR) were used for gross target volume (GTV) contouring. Five radiation oncologists independently contoured GTVs on pre-treatment T1c and initial online-T1, T2, and FLAIR images. We assessed intra-observer and inter-observer variations and analysed the dosimetry impact through treatment planning based on GTVs generated by online MRI, simulating the current online adaptive radiotherapy practice. RESULTS: The average Dice Similarity Coefficient (DSC) for inter-observer comparison were 0.79, 0.54, 0.59, and 0.64 for pre-treatment T1c, online-T1, T2, and FLAIR, respectively. Inter-observer variations were significantly smaller for the 3.0 T pre-treatment T1c than for the contrast-free online 1.5 T MR scans (P < 0.001). Compared to the T1c contours, the average DSC index of intra-observer contouring was 0.52‒0.55 for online MRIs. For BMs larger than 3 cm3, visible on all image sets, the average DSC indices were 0.69, 0.71 and 0.64 for online-T1, T2, and FLAIR, respectively, compared to the pre-treatment T1c contour. For BMs < 3 cm3, the average visibility rates were 22.3%, 41.3%, and 51.8% for online-T1, T2, and FLAIR, respectively. Simulated adaptive planning showed an average prescription dose coverage of 63.4‒66.9% when evaluated by ground truth planning target volumes (PTVs) generated on pre-treatment T1c, reducing it from over 99% coverage by PTVs generated on online MRIs. CONCLUSIONS: The accuracy of online target contouring was unsatisfactory for the current MRI-guided online adaptive FSRT. Small lesions had poor visibility on 1.5 T non-contrast-enhanced MR-Linac images. Contour inaccuracies caused a one-third drop in prescription dose coverage for the target volume. Future studies should explore the feasibility of contrast agent administration during daily treatment in MRI-guided online adaptive FSRT procedures.

Commissioning and clinical evaluation of a novel high-resolution quality assurance digital detector array for SRS and SBRT.

PURPOSE: We aimed to perform the commissioning and clinical evaluation of myQA SRS detector array for patient-specific quality assurance (PSQA) of stereotactic radiosurgery (SRS)/ stereotactic body radiotherapy (SBRT) plans. METHODS: To perform the commissioning of myQA SRS, its dose linearity, dose-rate dependence, angular dependence, and field-size dependence were investigated. Ten SBRT plans were selected for clinical evaluation: 1) Common clinical deviations based on the original SBRT plan (Plan0), including multileaf collimator (MLC) positioning deviation and treatment positioning deviation were introduced. 2) Compared the performance of the myQA SRS and a high-resolution EPID dosimetry system in PSQA measurement for the SBRT plans. Evaluation parameters include gamma passing rate (GPR) and distance-to-agreement (DTA) pass rate (DPR). RESULTS: The dose linearity, angle dependence, and field-size dependence of myQA SRS system exhibit excellent performance. The myQA SRS is highly sensitive in the detection of MLC deviations. The GPR of (3%/1 mm) decreases from 90.4% of the original plan to 72.7%/62.9% with an MLC outward/inward deviation of 3 mm. Additionally, when the setup error deviates by 1 mm in the X, Y, and Z directions with the GPR of (3%/1 mm) decreasing by an average of -20.9%, -25.7%, and -24.7%, respectively, and DPR (1 mm) decreasing by an average of -33.7%, -32.9%, and -29.8%. Additionally, the myQA SRS has a slightly higher GPR than EPID for PSQA, However, the difference is not statistically significant with the GPR of (3%/1 mm) of (average 90.4%% vs. 90.1%, p = 0.414). CONCLUSION: Dosimetry characteristics of the myQA SRS device meets the accuracy and sensitivity requirement of PSQA for SRS/SBRT treatment. The dose rate dependence should be adequately calibrated before its application and a more stringent GPR (3%/1 mm) evaluation criterion is suggested when it is used for SRS/SBRT QA.

Evaluation of bladder filling effects on the dose distribution during radiotherapy for cervical cancer based on daily CT images.

PURPOSE: This study aimed to assess the effects of bladder filling during cervical cancer radiotherapy on target volume and organs at risk (OARs) dose based on daily computed tomography (daily-CT) images and provide bladder-volume-based dose prediction models. METHODS: Nineteen patients (475 daily-CTs) comprised the study group, and five patients comprised the validation set (25 daily-CTs). Target volumes and OARs were delineated on daily-CT images and the treatment plan was recalculated accordingly. The deviation from the planning bladder volume (DVB), the correlation between DVB and clinical (CTV)/planning (PTV) target volume in terms of prescribed dose coverage, and the relationship of small bowel volume and bladder dose with the ratio of bladder volume (RVB) were analyzed. RESULTS: In all cases, the prescribed dose coverage in the CTV was >95% when DVB was <200 cm3 , whereas that in the PTV was >95% when RVB was <160%. The ratio of bladder V45 Gy to the planning bladder V45 Gy (RBV45 ) exhibited a negative linear relationship with RVB (RBV45  = -0.18*RVB + 120.8; R2  = 0.80). Moreover, the ratio of small bowel volume to planning small bowel volume (RVS) exhibited a negative linear relationship with RVB (RVS = -1.06*RVB +217.59; R2  = 0.41). The validation set results showed that the linear model predicted well the effects of bladder volume changes on target volume coverage and bladder dose. CONCLUSIONS: This study assessed dosimetry and volume effects of bladder filling on target and OARs based on daily-CT images. We established a quantitative relationship between these parameters, providing dose prediction models for cervical cancer radiotherapy.

MR-based synthetic CT image for intensity-modulated proton treatment planning of nasopharyngeal carcinoma patients.

PURPOSE: To develop an advanced deep convolutional neural network (DCNN) architecture to generate synthetic CT (SCT) images from MR images for intensity-modulated proton therapy (IMPT) treatment planning of nasopharyngeal cancer (NPC) patients. METHODS: T1-weighted MR images and paired CT (PCT) images were obtained from 206 NPC patients. For each patient, deformable image registration was performed between MR and PCT images to create an MR-CT image pair. Thirty pairs were randomly chosen as the independent test set and the remaining 176 pairs (14 for validation and 162 for training) were used to build two conditional generative adversarial networks (GANs): 1) GAN3D: using a 3D U-net enhanced with residual connections and attentional mechanism as the generator and 2) GAN2D: using a 2D U-net as the generator. For each test patient, SCT images were generated using the generators with the MR images as input and were compared with respect to the corresponding PCT image. A clinical IMPT plan was created and optimized on the PCT image. The dose was recalculated on the SCT images and compared with the one calculated on the PCT image. RESULTS: The mean absolute errors (MAEs) between the PCT and SCT, within the body, were (64.89 ± 5.31) HU and (64.31 ± 4.61) HU for the GAN2D and GAN3D. Within the high-density bone (HU > 600), the GAN3D achieved a smaller MAE compared with the GAN2D (p < 0.001). Within the body, the absolute point dose deviation was reduced from (0.58 ± 1.61) Gy for the GAN2D to (0.47 ± 0.94) Gy for the GAN3D. The (3 mm/3%) gamma passing rates were above 97.32% for all SCT images. CONCLUSIONS: The SCT images generated using GANs achieved clinical acceptable dosimetric accuracy for IMPT of NPC patients. Using advanced DCNN architecture design, such as residual connections and attention mechanism, SCT image quality was further improved and resulted in a small dosimetric improvement.

Comparison of 3D and 2D gamma passing rate criteria for detection sensitivity to IMRT delivery errors.

This study compared three-dimensional (3D) and two-dimensional (2D) percentage gamma passing rates (%GPs) for detection sensitivity to IMRT delivery errors and investigated the correlation between two kinds of %GP. Eleven prostate IMRT cases were selected, and errors in multileaf collimator (MLC) bank sag, MLC leaf traveling, and machine output were simulated by recalculating the dose distributions in patients. 2D doses were extracted from the 3D doses at the isocenter position. The 3D and 2D %GPs with different gamma criteria were then obtained by comparing the recalculated and original doses in specific regions of interest (ROI), such as the whole body, the planning target volume (PTV), the bladder, and the rectum. The sensitivities to simulated errors of the two types of %GP were compared, and the correlation between the 2D and 3D %GPs for different ROIs were analyzed. For the whole-body evaluation, both the 2D and 3D %GPs with the 3%/3 mm criterion were above 90% for all tested MLC errors and for MU deviations up to 4%, and the 3D %GP was higher than the 2D %GP. In organ-specific evaluations, the PTV-specific 2D and 3D %GP gradients were -4.70% and -5.14% per millimeter of the MLC traveling error, and -17.79% and -20.50% per percentage of MU error, respectively. However, a stricter criterion (2%/1 mm) was needed to detect the tested MLC sag error. The Pearson correlation analysis showed a significant strong correlation (r > 0.8 and P < 0.001) between the 2D and 3D %GPs in the whole body and PTV-specific gamma evaluations. The whole-body %GP with the 3%/3 mm criterion was inadequate to detect the tested MLC and MU errors, and a stricter criterion may be needed. The PTV-specific gamma evaluation helped to improve the sensitivity of the error detection, especially using the 3D GP%.

Normal Tissue Complication Probability Model for Radiation-induced Temporal Lobe Injury after Intensity-modulated Radiation Therapy for Nasopharyngeal Carcinoma.

PURPOSE: To identify predictors for the development of temporal lobe injury (TLI) after intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma. MATERIALS AND METHODS: Data in 351 patients with nasopharyngeal carcinoma treated with IMRT were reviewed retrospectively according to institutional ethics committee approval. Clinical factors associated with TLI were analyzed. Dose-volume histograms for 550 evaluable temporal lobes were analyzed, and the predictive value of therapy-associated and patient-associated factors for the occurrence of TLI was evaluated. Survival curves were depicted by using the Kaplan-Meier method and compared by using the log-rank test. Logistic regression analysis was used for multivariate analyses. RESULTS: Median follow-up was 76 months (range, 6-100 months). Twenty-nine of 351 patients (8.3%) developed TLI; 21 patients had unilateral TLI, and eight had bilateral TLI. Median latency from IMRT until first TLI was 33 months (range, 12-83 months) among patients with TLI. The actuarial TLI-free survival rates were 94.4% and 91.3% at 3 and 5 years after radiation therapy, respectively. Logistic regression analysis demonstrated that dose delivered to a 1-cm(3) volume of the temporal lobe (D1cc) was the only independent predictor for TLI. The biologically equivalent tolerance doses at 2 Gy for a 5% and 50% probability of developing TLI were 62.83-Gy equivalents (95% confidence interval: 59.68, 65.97) and 77.58-Gy equivalents (95% confidence interval: 74.85, 80.32), respectively. CONCLUSION: D1cc is predictive for radiation-induced TLI, suggesting that delivery of a high dose of radiation to a small volume of the temporal lobe is unsafe. A D1cc of 62.83 Gy by using a correction formula for varying fraction size may be the dose tolerance of the temporal lobe.

Risk factors and prediction-score model for distant metastasis in nasopharyngeal carcinoma treated with intensity-modulated radiotherapy.

The objective of this study is to identify the risk factors and construct a prediction-score model for distant metastasis (DM) in nasopharyngeal carcinoma (NPC) patients treated with intensity-modulated radiotherapy (IMRT). A total of 520 nonmetastatic NPC patients were analysed retrospectively. The independent risk factors for DM were tested by multivariate Cox regression analysis. The prediction-score model was established according to the regression coefficient. The median follow-up was 88.4 months. The 5-year DM rate was 15.1%. N2-3, primary tumour volume of nasopharynx (GTVnx) >24.56 cm(3), haemoglobin change after treatment (ΔHGB) >25.8 g/L, albumin-globulin ratio (AGR) ≤1.34, pretreatment neutrophil-lymphocyte ratio (NLR) >2.81 and pretreatment serum lactate dehydrogenase (LDH) >245 U/L were significantly adverse independent predictive factors for DM. Three subgroups were defined based on the prediction-score model: low risk (0-2), intermediate risk (3-4) and high risk (5-8). The 5-year DM rates were 4.6, 21.8 and 50.8%, respectively (P < 0.001). The areas under the curve for DM in the prediction-score model and the UICC/AJCC staging system seventh edition were 0.748 and 0.627, respectively (P < 0.001). The scoring model is useful in evaluating the risk of DM in IMRT-treated NPC patients and guiding future therapeutic trials. Further prospective study is needed.

Effect of total dose and fraction size on survival of patients with locally recurrent nasopharyngeal carcinoma treated with intensity-modulated radiotherapy: a phase 2, single-center, randomized controlled trial.

BACKGROUND: The optimal model of total dose and fraction size for patients with locally recurrent nasopharyngeal carcinoma treated with intensity-modulated radiotherapy (IMRT) remains unclear. The authors designed a randomized phase 2 clinical trial to investigate the efficacy of 2 different models, with the objective of determining an optimal model. METHODS: Between January 2003 and December 2007, a total of 117 patients with locally recurrent nonmetastatic nasopharyngeal carcinoma were randomized to 2 different models of total dose and fraction size: group A (59 patients) received 60 gray in 27 fractions and group B (58 patients) received 68 gray in 34 fractions. Both groups received 5 daily fractions per week. All patients received IMRT alone. RESULTS: The median follow-up was 25.0 months. The 5-year overall survival in group A was higher than that in group B (44.2% vs 30.3%; P =.06), and the local failure-free survival in group A was slightly lower than that in group B (63.7% vs 71.0%; P =.41). Severe late complications were the main cause of death. The incidences of mucosal necrosis and massive hemorrhage in patients in group B were significantly higher than those among patients in group A at 50.8% versus 28.8% (P =.02) and 31.0% versus 18.6% (P =.12), respectively. Tumor volume (P<.01) and model of total dose and fraction size (P =.03) were found to be significant factors for mucosal necrosis and massive hemorrhage. CONCLUSIONS: Appropriately decreasing the total dose and increasing the fraction size can achieve local control similar to that achieved with a higher dose after IMRT; furthermore, it can improve overall survival by significantly reducing the incidence of severe late complications including mucosal necrosis and massive hemorrhage.

Intensity-modulated radiotherapy for stage IVA/IVB nasopharyngeal carcinoma: clinical outcomes and patterns of failure in an endemic area in China.

PURPOSE: The purpose of this study was to analyze the mode of relapse patterns and survival of 209 patients with stage IVA and IVB nasopharyngeal carcinoma (NPC). PATIENTS AND MATERIALS: A total of 209 patients who underwent magnetic resonance imaging (MRI) and were subsequently histologically diagnosed with nondisseminated stage IV NPC received intensity-modulated radiotherapy (IMRT) as their primary treatment and were included in this retrospective study. RESULTS: Median follow-up time was 65 months (range, 3-108 months). The 5-year overall survival (OS), disease-free survival (DFS), local recurrence-free survival (LRFS), locoregional recurrence-free survival (LRRFS), and distant metastasis-free survival (DMFS) rates for patients with stage IVA and stage IVB NPC were 72.7 vs. 60.0 % (p = 0.319), 62.9 vs. 51.3 % (p = 0.070), 82.9 vs. 93.1 % (p = 0.070), 82.9 vs. 82.9 % (p = 0.897), 76.4 vs. 58.5 % (p = 0.003), respectively. Age older than 44 years was found to be a statistically significant adverse independent prognostic factor for OS. Patients with advanced N status had worse OS, DFS, and DMFS rates. Patients with a primary gross tumor volume (GTV-P) ≥ 55.11 ml had worse OS, DFS, and LRRFS rates. CONCLUSION: The results of treating stage IVA NPC with IMRT were excellent. Distant metastasis remains the most difficult treatment challenge for patients with stage IVA and IVB NPC, and more effective systemic chemotherapy should be explored.

The individualized delineation of clinical target volume for primary nasopharyngeal carcinoma based on invasion risk of substructures: A prospective, real-world study with a large population.

BACKGROUND AND PURPOSE: The delineation of clinical target volume (CTV) for primary nasopharyngeal carcinoma (NPC) is currently controversial and the international guideline still recommend a uniform border for CTV regardless of the tumor extent. We conducted this prospective, real-world study to evaluate the clinical outcomes of our individualized CTV delineation method based on distance plus substructures. MATERIALS AND METHODS: We preliminarily investigated the local extension patterns of NPC on 354 newly diagnosed patients and defined the structures surrounding the nasopharynx as Level-1 to Level-4 substructures stratified by the risk of invasion. We then enrolled patients with newly diagnosed NPC without distant metastasis to investigate our individualized CTV delineation protocol. All patients received intensity modulated radiotherapy. CTV1 and CTV2 were prescribed doses of 60 Gy and 54 Gy in 30 âˆ¼ 33 fractions. The primary endpoint was local recurrence-free survival (LRFS); secondary endpoints included regional control and survival, estimated using the Kaplan-Meier method. The local failure patterns were also analyzed. RESULTS: From January 2008 to December 2012 and from January 2013 to September 2019, 356 and 648 patients were enrolled, named as training set and validation set, respectively. With a median follow-up of 104.6 (interquartile, 73.1-126.9) and 51.4 (39.5-78.5) months, 31 (8.7 %) and 38 (5.9 %) patients in training and validation sets experienced local recurrence, and the 5-year LRFS was 93.0 % and 93.2 %, respectively; 63 (17.7 %) and 39 (6 %) patients died in training and validation sets, and the 5-year overall survival (OS) was 88.5 % and 93.4 %, respectively. For the whole study cohort (N = 1004) with a median follow-up of 66.6 (41.5-98.0) months, the 5-year LRFS and OS was 93.2 % and 91.5 %. The grade 3 late toxicities included xerostomia, subcutaneous fibrosis, hearing impairment, trismus, visuality impairment and skin atrophy, with a total incidence of 1.5 %. Sixty-seven of 69 (97.1 %) local recurrence was in high-dose area. CONCLUSION: Our individualized CTV delineation method can achieve favorable local tumor control and long-term survival outcomes with acceptable late toxicities.

Improved accuracy of auto-segmentation of organs at risk in radiotherapy planning for nasopharyngeal carcinoma based on fully convolutional neural network deep learning.

OBJECTIVE: We examined a modified encoder-decoder architecture-based fully convolutional neural network, OrganNet, for simultaneous auto-segmentation of 24 organs at risk (OARs) in the head and neck, followed by validation tests and evaluation of clinical application. MATERIALS AND METHODS: Computed tomography (CT) images from 310 radiotherapy plans were used as the experimental data set, of which 260 and 50 were used as the training and test sets, respectively. An improved U-Net architecture was established by introducing a batch normalization layer, residual squeeze-and-excitation layer, and unique organ-specific loss function for deep learning training. The performance of the trained network model was evaluated by comparing the manual-delineation and the STAPLE contour of 10 physicians from different centers. RESULTS: Our model achieved good segmentation in all 24 OARs in nasopharyngeal cancer radiotherapy plan CT images, with an average Dice similarity coefficient of 83.75%. Specifically, the mean Dice coefficients in large-volume organs (brainstem, spinal cord, left/right parotid glands, left/right temporal lobes, and left/right mandibles) were 84.97% - 95.00%, and in small-volume organs (pituitary, lens, optic nerve, and optic chiasma) were 55.46% - 91.56%. respectively. Using the STAPLE contours as standard contour, the OrganNet achieved comparable or better DICE in organ segmentation then that of the manual-delineation as well. CONCLUSION: The established OrganNet enables simultaneous automatic segmentation of multiple targets on CT images of the head and neck radiotherapy plans, effectively improves the accuracy of U-Net based segmentation for OARs, especially for small-volume organs.

The m6A reader IGF2BP3 preserves NOTCH3 mRNA stability to sustain Notch3 signaling and promote tumor metastasis in nasopharyngeal carcinoma.

Metastasis remains the major cause of treatment failure in patients with nasopharyngeal carcinoma (NPC), in which sustained activation of the Notch signaling plays a critical role. N6-Methyladenosine (m6A)-mediated post-transcriptional regulation is involved in fine-tuning the Notch signaling output; however, the post-transcriptional mechanisms underlying NPC metastasis remain poorly understood. In the present study, we report that insulin-like growth factor 2 mRNA-binding proteins 3 (IGF2BP3) serves as a key m6A reader in NPC. IGF2BP3 expression was significantly upregulated in metastatic NPC and correlated with poor prognosis in patients with NPC. IGF2BP3 overexpression promoted, while IGF2BP3 downregulation inhibited tumor metastasis and the stemness phenotype of NPC cells in vitro and in vivo. Mechanistically, IGF2BP3 maintains NOTCH3 mRNA stability via suppression of CCR4-NOT complex-mediated deadenylation in an m6A-dependent manner, which sustains Notch3 signaling activation and increases the transcription of stemness-associated downstream genes, eventually promoting tumor metastasis. Our findings highlight the pro-metastatic function of the IGF2BP3/Notch3 axis and revealed the precise role of IGF2BP3 in post-transcriptional regulation of NOTCH3, suggesting IGF2BP3 as a novel prognostic biomarker and potential therapeutic target in NPC metastasis.

Comparison of intratumor and local immune response between MV X-ray FLASH and conventional radiotherapies.

Background/Purpose: Investigating the antitumor effect and intratumor as well as local immune response in breast cancer-bearing mice after MV X-ray ultra-high dose rate radiotherapy (FLASH-RT) and conventional dose rate radiotherapy (CONV-RT). Materials/Methods: Six-week-old female C57BL/6 mice were inoculated subcutaneously with Py8119 and Py230 breast tumor cells in the inguinal mammary gland and administered 10 Gy abdominal 6 MV X-ray FLASH-RT (125 Gy/s) or CONV-RT (0.2 Gy/s) 15 days after tumor inoculation. Tumor and spleen tissues were obtained at different time points post-irradiation (PI) for analysis of immune cell infiltration using flow cytometry and immunohistochemical (IHC) staining. Intestine tissues were collected 3 days PI to evaluate normal tissue damage and immune cell infiltration. Results: Both FLASH-RT and CONV-RT significantly delayed tumor growth. Flow cytometry showed increased CD8+/CD3 + and CD8+/CD4 + ratios, and IHC confirmed a similar increased CD8 + T cell infiltration at 2 weeks PI in Py8119 tumor tissues in both irradiation groups. No statistical difference was observed between the irradiation groups in terms of tumor growth and increased T cell infiltration in the tumor. Unexpectedly, significantly smaller spleen weight and substantially higher CD8+/CD3 + and lower CD4+/CD3 + ratios were observed in the spleens of the FLASH-RT group than in the spleens of the non-irradiated control and CONV-RT groups 4 weeks PI. Pathological analysis revealed severe red pulp expansion in several spleens from the CONV-RT group, but not in the spleens of the FLASH-RT group. Reduced intestinal damage, macrophage and neutrophil infiltration were observed in the FLASH-RT group compared with CONV-RT group. Conclusions: FLASH-RT and CONV-RT effectively suppressed tumor growth and promoted CD8 + T cell influx into tumors. FLASH-RT can induce different splenic immune responses and reduce radiation-induced damage in the spleen and intestine, which may potentially enhance the therapeutic ratio of FLASH-RT.

Long noncoding RNA LINC00173 induces radioresistance in nasopharyngeal carcinoma via inhibiting CHK2/P53 pathway.

Radiotherapy is the backbone of nasopharyngeal carcinoma (NPC), nearly 11-17% NPC patients suffered local relapse and 18-37% suffered distant metastasis mainly due to radioresistance. Therefore, the key of improving patients' survivals is to investigate the mechanism of radioresistance. In this study, we revealed that the expression level of long intergenic nonprotein coding RNA 173 (LINC00173) was significantly increased in the radioresistant NPC patients' tumour tissues compared with the radiosensitive patients by RNA-sequencing, which also predict poor prognosis in NPC. Overexpression of LINC00173 induced radioresistance of NPC cells in vitro and in vivo. Mechanistically, LINC00173 bound with checkpoint kinase 2 (CHK2) in nucleus, and impaired the irradiation-induced CHK2 phosphorylation, then suppressed the activation of P53 signalling pathway, which eventually inhibiting apoptosis and leading to radioresistance in NPC cells. In summary, LINC00173 decreases the occurrence of apoptosis through inhibiting the CHK2/P53 pathway, leads to NPC radioresistance and could be considered as a novel predictor and therapeutic target in NPC.

Efficacy of concurrent chemoradiotherapy alone for loco-regionally advanced nasopharyngeal carcinoma: long-term follow-up analysis.

BACKGROUND: To analysis the clinical outcomes of concurrent chemoradiotherapy (CCRT) alone based on 10-year results for loco-regionally advanced nasopharyngeal carcinoma (LANPC), so as to provide evidence for individualized treatment strategy and designing appropriate clinical trial for different risk LANPC patients. METHODS: Consecutive patients with stage III-IVa (AJCC/UICC 8th) were enrolled in this study. All patients received radical intensity-modulated radiotherapy (IMRT) and concurrent cisplatin chemotherapy (CDDP). The hazard ratios (HRs) of death risk in patients with T3N0 was used as baseline, relative HRs were calculated by a Cox proportional hazard model to classify different death risk patients. Survival curves for the time-to-event endpoints were analyzed by the Kaplan-Meier method and compared using the log-rank test. All statistical tests were conducted at a two-sided level of significance of 0.05. RESULTS: A total of 456 eligible patients were included. With 12-year median follow-up, 10-year overall survival (OS) was 76%. 10-year loco-regionally failure-free survival (LR-FFS), distant failure-free survival (D-FFS) and failure-free survival (FFS) were 72%, 73% and 70%, respectively. Based on the relative hazard ratios (HRs) of death risk, LANPC patients were classified into 3 subgroups, low-risk group (T1-2N2 and T3N0-1) contained 244 patients with HR < 2; medium-risk group (T3N2 and T4N0-1) contained 140 patients with HR of 2 - 5; high-risk group (T4N2 and T1-4N3) contained 72 patients with HR > 5. The 10-year OS for patients in low-, medium-, and high-risk group were 86%, 71% and 52%, respectively. Significantly differences of OS rates were found between each of the two groups (low-risk group vs. medium-risk group, P < 0.001; low-risk group vs. high-risk group, P < 0.001; and medium-risk group vs. high-risk group, P = 0.002, respectively). Grade 3-4 late toxicities included deafness/otitis (9%), xerostomia (4%), temporal lobe injury (5%), cranial neuropathy (4%), peripheral neuropathy (2%), soft tissue damage (2%) and trismus (1%). CONCLUSIONS: Our classification criteria demonstrated that significant heterogeneity in death risk among TN substages for LANPC patients. IMRT plus CDDP alone maybe suitable for low-risk LANPC (T1-2N2 or T3N0-1), but not for medium- and high-risk patients. These prognostic groupings provide a practicable anatomic foundation to guide individualized treatment and select optimal targeting in the future clinical trials.

A real-time in vivo dosimetric verification method for high-dose rate intracavitary brachytherapy of nasopharyngeal carcinoma.

PURPOSE: A real-time in vivo dosimetric verification method using metal-oxide-semiconductor field effect transistor (MOSFET) dosimeters has been developed for patient dosimetry in high-dose rate (HDR) intracavitary brachytherapy of nasopharyngeal carcinoma (NPC). METHODS: The necessary calibration and correction factors for MOSFET measurements in (192)Iridium source were determined in a water phantom. With the detector placed inside a custom-made nasopharyngeal applicator, the actual dose delivered to the tumor was measured in vivo and compared to the calculated values using a commercial brachytherapy planning system. RESULTS: Five MOSFETs were independently calibrated with the HDR source, yielding calibration factors of 0.48 ± 0.007 cGy∕mV. The maximum sensitivity variation was no more than 7% in the clinically relevant distance range of 1-5 cm from the source. A total of 70 in vivo measurements in 11 NPC patients demonstrated good agreement with the treatment planning. The mean differences between the planned and the actually delivered dose within a single treatment fraction were -0.1% ± 3.8% and -0.1% ± 3.7%, respectively, for right and left side assessments. The maximum dose deviation was less than 8.5%. CONCLUSIONS: In vivo measurement using the real-time MOSFET dosimetry system is possible to evaluate the actual dose to the tumor received by the patient during a treatment fraction and thus can offer another line of security to detect and prevent large errors.

Comparison of Absolute Dose Achievable Between Helical Tomotherapy and RapidArc in Total Dura Mater Irradiation for Child Cancer.

Background and Purpose: In this study, the absolute dose achievable between helical tomotherapy (HT) plans and RapidArc (RA) plans for total dura mater irradiation (TDMI) was compared. Materials and methods: A planning study was conducted on nine children's case datasets with dura mater metastasis of neuroblastoma. The target included the entire calvarium and skull base and formed a closed volume with a certain thickness around the brain. HT and RA plans with four coplanar full arcs (RA4) with half-field technique were generated for the comparison of absolute dose achievable. In total, 30.6 Gy was prescribed as D95% (ie, dose to 95% of PTV volume). Results: In the dosimetric comparison between the two modalities, HT provided more homogenous dose distribution than RA4 (mean HI5-95%: 1.046 vs 1.088, P < .001). The V107% and D2Gy of PTV in HT versus RA4 were 3.06% versus 30.47% and 32.59 Gy versus 33.45 Gy, respectively. HT reduced the Dmean and V5Gy of the brain, brainstem, and hippocampus by 25%-48% and 27%-56% compared with RA4, respectively. Conclusion: Both techniques could provide sufficient coverage for targets, but HT offered more homogenous dose to PTV and lower dose to the central region of the brain involving the brainstem and hippocampus. RA4 could be completed in a shorter time with lower MUs, but with relatively higher dose to the brain or hippocampus. In terms of dosimetry, HT may improve long-term cognitive decline in these young pediatric patients with TDMI.

Radioprotective effect of X-ray abdominal FLASH irradiation: Adaptation to oxidative damage and inflammatory response may be benefiting factors.

BACKGROUND: Ultrahigh dose-rate irradiation (FLASH-IR) was reported to be efficient in tumor control while reducing normal tissue radiotoxicity. However, the mechanism of such phenomenon is still unclear. Besides, the FLASH experiments using high energy X-ray, the most common modality in clinical radiotherapy, are rarely reported. This study aims to investigate the radiobiological response using 6 MV X-ray FLASH-IR or conventional dose-rate IR (CONV-IR). METHODS: The superconducting linac of Chengdu THz Free Electron Laser (CTFEL) facility was used for FLASH-IR, a diamond radiation detector and a CeBr3 scintillation detector were used to monitor the time structure and dose rate of FLASH pulses. BALB/c nude mice received whole abdominal 6 MV X-ray FLASH-IR or CONV-IR, the prescribed dose was 15 Gy or 10 Gy and the delivered absolute dose was monitored with EBT3 films. The mice were either euthanized 24 h post-IR to evaluate acute tissue responses or followed up for 6 weeks to observe late-stage responses and survival probability. Complete blood count, histological analyses, and measurement of cytokine expression and redox status were performed. RESULTS: The mean dose rate of >150 Gy/s and instantaneous dose rate of >5.5 × 105  Gy/s was reached in FLASH-IR at the center of mice body. After 6 weeks' follow-up of mice that received 15 Gy IR, the FLASH group showed faster body weight recovery and higher survival probability than the CONV group. Histological analysis showed that FLASH-IR induced less acute intestinal damage than CONV-IR. Complete blood count and cytokine concentration measurement found that the inflammatory blood cell counts and pro-inflammatory cytokine concentrations were elevated at the acute stage after both FLASH-IR and CONV-IR. However, FLASH irradiated mice had significantly fewer inflammatory blood cells and diminished pro-inflammatory cytokine at the late stage. Moreover, higher reactive oxygen species (ROS) signal intensities but significantly reduced lipid peroxidation were found in the FLASH group than in the CONV group in the acute stage. CONCLUSIONS: The radioprotective effect of 6 MV X-ray FLASH-IR was observed. The differences in inflammatory responses and redox status between the two groups may be the factors responsible for reduced radiotoxicities following FLASH-IR. Further studies are required to thoroughly evaluate the impact of ROS on FLASH effect.

Long-term Survivals, Toxicities and the Role of Chemotherapy in Early-Stage Nasopharyngeal Carcinoma Patients Treated with Intensity-Modulated Radiation Therapy: A Retrospective Study with 15-Year Follow-up.

PURPOSE: This study was aimed to investigate long-term survivals and toxicities of early-stage nasopharyngeal carcinoma (NPC) in endemic area, evaluating the role of chemotherapy in stage II patients. MATERIALS AND METHODS: Totally 187 patients with newly diagnosed NPC and restaged American Joint Committee on Cancer/International Union Against Cancer 8th T1-2N0-1M0 were retrospectively recruited. All received intensity-modulated radiotherapy (IMRT)±chemotherapy (CT) from 2001 to 2010. RESULTS: With 15.7-year median follow-up, 10-year locoregional recurrence-free survival, distant metastasis-free survival (DMFS), disease-specific survival (DSS), and overall survival (OS) were 93.3%, 93.5%, 92.9% and 88.2%, respectively. Multivariable analyses showed cervical lymph nodes positive and pre-treatment prognostic nutritional index ≥ 52.0 could independently predict DMFS (p=0.036 and p=0.011), DSS (p=0.014 and p=0.026), and OS (p=0.002 and p < 0.001); Charlson comorbidity index < 3 points could predict DSS (p=0.011); age > 45 years (p=0.002) and pre-treatment lactate dehydrogenase ≥ 240 U/L (p < 0.001) predicted OS. No grade 4 late toxicity happened; grade 3 late toxicities included subcutaneous fibrosis (4.3%), deafness or otitis (4.8%), skin dystrophy (2.1%), and xerostomia (1.1%). No differences on survivals were shown between IMRT+CT vs. IMRT alone in stage II patients, even in T2N1M0 (p > 0.05). Unsurprising, patients in IMRT+CT had more acute gastrointestinal reaction, myelosuppression, mucositis, late ear toxicity, and cranial nerve injury (all p < 0.05) than IMRT alone group. CONCLUSION: Superior tumor control and satisfying long-term outcomes could be achieved with IMRT in early-stage NPC with mild late toxicities. As CT would bring more toxicities, it should be carefully performed to stage II patients.

Impact on xerostomia for nasopharyngeal carcinoma patients treated with superficial parotid lobe-sparing intensity-modulated radiation therapy (SPLS-IMRT): A prospective phase II randomized controlled study.

PURPOSE: To compare the incidence of xerostomia in nasopharyngeal carcinoma (NPC) patients treated with superficial parotid lobe-sparing intensity-modulated radiation therapy (SPLS-IMRT) and conventional IMRT (C-IMRT). METHODS: Patients with histologically confirmed NPC who met the eligibility criteria were randomly assigned to receive either SPLS-IMRT or C-IMRT. The primary endpoint was the incidence of xerostomia at 12 months post-IMRT. The secondary endpoints included the xerostomia questionnaire (XQ) score, unstimulated salivary flow rate (USFR), stimulated salivary flow rate (SSFR), and survival outcomes. RESULTS: Ninety patients were enrolled. Eighty-two patients were included for xerostomia analysis (42 in the SPLS-IMRT group and 40 in the C-IMRT group). At 12 months post-IMRT, the incidence of xerostomia in the SPLS-IMRT group was significantly lower than that in the C-IMRT group (83.4% vs 95.0%; P = 0.007), especially the grade 3 xerostomia (0% vs 12.5%; P < 0.001). The median change in XQ score was similar between the two groups (11.9 points vs 14.1 points; P = 0.194). There was a significantly higher median fractional USFR (0.67 vs 0.35; P = 0.024) and SSFR (0.66 vs 0.32; P = 0.021) in the SPLS-IMRT group than the C-IMRT group. The 3-year LRRFS, DMFS, and OS in the SPLS-IMRT and C-IMRT groups were 92.5% vs 90.9%, 83.8% vs 81.7%, and 88.9% vs 88.2% (all P > 0.05). CONCLUSION: SPLS-IMRT significantly reduced the incidence of xerostomia at 12 months post-IMRT in NPC by recovering parotid gland function earlier than C-IMRT, without compromising survivals. Phase III clinical trials are warranted. (ClinicalTrials.gov, number NCT05020067).