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Radiation-induced temporal lobe necrosis (TLN) is one of the late post-radiotherapy complications in nasopharyngeal cancer (NPC) patients. Since NPC is common to have skull base infiltration, irradiation of the temporal lobes is inevitable despite the use of the more advanced intensity-modulated radiotherapy (IMRT). Moreover, the diagnosis and treatment of TLN remain challenging. In this review, we discuss the diagnosis of TLN with conventional and advanced imaging modalities, onset and predictive parameters of TLN development, the impact of IMRT on TLN in terms of incidence and dosimetric analyzes, and the recent advancements in the treatment of TLN. [ABSTRACT FROM AUTHOR]

Introduction: Previous studies have shown that the beam arrangement had significant influence on plan quality in intensity modulated radiotherapy (IMRT). This study aimed to evaluate the dosimetric performance of beam arrangement methods by employing equally spaced beams (ESB), beam angle optimization (BAO), and volumetric modulated arc therapy (VMAT) in the planning of five types of head and neck (H&N) cancers treated by IMRT. Methods: Five plans of different beam arrangement methods were optimized for 119 H&N cancer patients with the prescription of 66–70 Gy for high‐risk planning target volume (PTV), 60 Gy for intermediate risk PTV, 54 Gy for low‐risk PTV using a simultaneously integrated boost method. The five‐beam arrangement methods were: ESB, coplanar BAO (BAOc), noncoplanar BAO (BAOnc), two‐arc VMAT (VMAT2), and three‐arc VMAT (VMAT3). The H&N cancers included cancers of nasopharynx, oral cavity, larynx, maxillary sinus, and parotid. Although the partial arc VMAT could be used in cases where the PTVs were situated at one side of the head such as the parotid, this arrangement was not included because it was intended to include only the beam arrangements that were applicable to all the types of head and neck cancers in the study. The plans were evaluated using a "figure‐of‐merit" known as uncomplicated target conformity index (UTCI). In addition, PTV conformation number and homogeneity index, normal tissue integral dose, and organ at risk (OAR) doses were also used. The mean values of these parameters were compared among the five plans. Results: All treatment plans met the preset dose requirements for the target volumes and OARs. For nasopharyngeal cancer, VMAT3 and BAOnc demonstrated significantly higher UTCI. For cancer of oral cavity, most beam arrangement showed similar UTCI except ESB, which was relatively lower. For cancer of larynx, there was no significant difference in UTCI among the five‐beam arrangement methods. For cancers of maxillary sinus and parotid gland, the two BAO methods showed marginally higher UTCI among all the five methods. Conclusion: Individual methods showed dosimetric advantages on certain aspects, and the UTCI of the BAO treatment plans are marginally greater in the case of maxillary sinus and parotid gland. However, if treatment time was included into consideration, VMAT plans would be recommended for cancers of the nasopharynx, oral cavity, and larynx. [ABSTRACT FROM AUTHOR]

Objectives: Radiation-induced hypothyroidism is the most common thyroid disorder after radiotherapy in nasopharyngeal carcinoma (NPC) patients. This study evaluated the pattern of radiation-induced thyroid gland changes in 48 months after radiotherapy in NPC patients and the association of hypothyroidism incidence with thyroid dose. Methods: Fifty-six NPC patients treated by intensity modulated radiotherapy in 2013 were recruited. All patients received baseline thyroid hormones (fT3, fT4 and TSH) tests and CT scan before radiotherapy. Repeated measures of the thyroid hormones and gland volume were performed at 3, 6, 12, 18, 24, 30, 36 and 48 months after treatment. Trend lines of the thyroid volume and hormone level changes against time were plotted. The incidence of hypothyroidism patients and its relationship with the dose were also evaluated. Results: The mean thyroid volume followed a decreasing trend after radiotherapy, reaching a minimum (-39.8%) at 30 months and slightly increased afterward. The fT4 level followed a similar pattern with its mean value dropped by 21.5% at 30 months and became steady after 36 months. TSH level showed gradual rise from just after radiotherapy, reaching a peak at 24 months and became relatively steady after 36 months. The incidence of hypothyroidism increased to a maximum at 24 months (28.6%) and dropped afterwards. Thyroid Dmean and D50 were significantly correlated with hypothyroidism incidence in 12 to 30 months (ρ > 0.40, p < 0.05). Conclusion: The patterns of radiation induced thyroid volume shrinkage and fT4 level reduction were similar, with both of them showed decreasing trend from 0 to 30 months. The thyroid volume and function reached a relatively steady state after 36 months. The incidence of hypothyroidism increased up to 24 months and its frequency was associated with the thyroid dose. [ABSTRACT FROM AUTHOR]

Background: The objectives of this study were to build a normal tissue complication probability (NTCP) model of radiation-induced hypothyroidism (RHT) for nasopharyngeal carcinoma (NPC) patients and to compare it with other four published NTCP models to evaluate its efficacy.Methods: Medical notes of 174 NPC patients after radiotherapy were reviewed. Biochemical hypothyroidism was defined as an elevated level of serum thyroid-stimulating hormone (TSH) value with a normal or decreased level of serum free thyroxine (fT4) after radiotherapy. Logistic regression with leave-one-out cross-validation was performed to establish the NTCP model. Model performance was evaluated and compared by the area under the receiver operating characteristic curve (AUC) in our NPC cohort.Results: With a median follow-up of 24 months, 39 (22.4%) patients developed biochemical hypothyroidism. Gender, chemotherapy, the percentage thyroid volume receiving more than 50 Gy (V50), and the maximum dose of the pituitary (Pmax) were identified as the most predictive factors for RHT. A NTCP model based on these four parameters were developed. The model comparison was made in our NPC cohort and our NTCP model performed better in RHT prediction than the other four models.Conclusions: This study developed a four-variable NTCP model for biochemical hypothyroidism in NPC patients post-radiotherapy. Our NTCP model for RHT presents a high prediction capability.Trial Registration: This is a retrospective study without registration. [ABSTRACT FROM AUTHOR]

Background: In intensity modulated radiotherapy (IMRT) of nasopharyngeal carcinoma (NPC), accurate delineation of the gross tumour volume (GTV) is important. Image registration of CT and MRI has been routinely used in treatment planning. With recent development of positron emission tomography (PET), the aims of this study were to evaluate the impact of PET on GTV delineation and dosimetric outcome in IMRT of early stage NPC patients.Methods: Twenty NPC patients with T1 or T2 disease treated by IMRT were recruited. For each patient, 2 sets of NP GTVs were delineated separately, in which one set was performed using CT and MRI registration only (GTVCM), while the other set was carried out using PET, CT and MRI information (GTVCMP). A 9-field IMRT plan was computed based on the target volumes generated from CT and MRI (PTVCM). To assess the geometric difference between the GTVCM and GTVCMP, GTV volumes and DICE similarity coefficient (DSC), which measured the geometrical similarity between the two GTVs, were recorded. To evaluate the dosimetric impact, the Dmax, Dmin, Dmean and D95 of PTVs were obtained from their dose volume histograms generated by the treatment planning system.Results: The overall mean volume of GTVCMP was greater than GTVCM by 4.4 %, in which GTVCMP was slightly greater in the T1 group but lower in the T2 group. The mean DSC of the whole group was 0.79 ± 0.05. Similar mean DSC values were also obtained from the T1 and T2 groups separately. The dosimetric parameters of PTVCM fulfilled the planning requirements. When applying this plan to the PTVCMP, the average Dmin (56.9 Gy) and D95 (68.6 Gy) of PTVCMP failed to meet the dose requirements and demonstrated significant differences from the PTVCM (p = 0.001 and 0.016 respectively), whereas the doses to GTVCMP did not show significant difference with the GTVCM.Conclusion: In IMRT of early stage NPC, PET was an important imaging modality in radiotherapy planning so as to avoid underdosing the PTV, although its effect on GTV delineation was not significant. It was recommended that PET images should be included in the treatment planning of NPC patients. [ABSTRACT FROM AUTHOR]

Objective: This study evaluated the potential benefit of a split-parotid delineation approach on the parotid gland in the treatment planning of patients with nasopharyn-geal carcinoma (NPC). Methods: 50 patients with NPC with parapharyngeal space (PPS) and/or level lla cervical node involvements were divided into three groups: PPS only, level lla cervical node only and both. Two volumetric-modulated arc therapy plans were computed. The first plan (control) was generated based on the routine treatment-planning protocol, while the second plan (test) was computed with the split-parotid delineation approach, in which a line through the anterolateral margin of the retromandibular vein was created that divided the parotid gland into anterolateral and posteromedial subsegments. For the test plan, the anterolateral subsegment was prescribed, with a dose constraint of 25 Gy in the plan optimization. Dosimetric data of the parotid gland, target volumes and selected organs at risk (OARs) were compared between the control and test plans. Results: The mean dose to the anterolateral subsegment of the parotid gland in all three groups was kept below 25 Gy. The test plan demonstrated significantly lower mean parotid dose than the control plan in the entire gland and the anterolateral subsegment in all three groups. The difference was the greatest in Group 3. Conclusion: The split-parotid delineation approach significantly lowered the mean dose to the anterolateral subsegment and overall gland without greatly compromising the doses to target volumes and other OARs. The effect was more obvious for both PPS and level lla cervical node involvements than for either of them alone. Advances in knowledge: It is the first article based on the assumption that parotid gland stem cells are situated at the anterolateral segment of the gland, and applied the split-parotid delineation approach to the parotid gland in the treatment planning of patients with NPC with PPS and level lla cervical node involvements, so that the function of the post-radiotherapy parotid gland might be better preserved. [ABSTRACT FROM AUTHOR]

Objective: To determine the predictors of the extent of carotid atherosclerosis in patients treated with radiotherapy (RT) for nasopharyngeal carcinoma (NPC). Methods: The present study investigated 129 post-RT NPC patients. Carotid atherosclerotic parameters, such as carotid intima-media thickness, carotid arterial stiffness and carotid plaque burden (plaque score, the presence of plaque and ≥50% stenosis) were assessed using ultrasonography. The association between carotid atherosclerotic parameters and nine potential predictors, including age, gender, post-RT duration, radiation dose, chemotherapy, diabetes mellitus, hypertension, hypercholesterolemia, and smoking, were determined using multiple regression. The cutoff values of age, post-RT duration and number of cardiovascular risk factors for the presence of carotid plaque or ≥50% carotid stenosis were analyzed using receiver operating characteristic (ROC) curve analysis. Multiple testing was corrected using Benjamini-Hochberg false discovery rate. Results: Age, post-RT duration and number of cardiovascular risk factors were significantly associated with carotid plaque burden (corrected P value, Pcor<0.05). Age of 44.5 years (sensitivity = 99.2% and specificity = 50%, Pcor<0.01) and post-RT duration of 8.5 years (sensitivity = 75.7% and specificity = 64.3%, Pcor<0.001) were the cutoff values for detecting carotid plaque, while post-RT duration of 13.5 years (sensitivity = 66.7% and specificity = 71.6%, Pcor<0.001) and 1.5 cardiovascular risk factors (sensitivity = 40.7% and specificity = 84.3%, Pcor<0.05) were the cutoff values for screening ≥50% carotid stenosis. Conclusions: Age, post-RT duration and number of cardiovascular risk factors are significant predictors of carotid atherosclerosis in post-RT NPC patients. Post-RT NPC patients, who are at least 45 years old, with post-RT duration of 9 years or above, and/or have ≥2 cardiovascular risk factors, are more susceptible to carotid atherosclerosis. [ABSTRACT FROM AUTHOR]

Introduction Radiation-induced thyroid dysfunction after radiotherapy for nasopharyngeal cancer ( NPC) has been reported. This study investigated the radiation effects of the thyroid and pituitary glands on thyroid function after radiotherapy for NPC. Methods Sixty-five NPC patients treated with radiotherapy were recruited. Baseline thyroid hormone levels comprising free triiodothyronine ( fT3), free thyroxine ( fT4) and thyroid-stimulating hormone ( TSH) were taken before treatment and at 3, 6, 12 and 18 months. A seven-beam intensity-modulated radiotherapy plan was generated for each patient. Thyroid and pituitary gland dose volume histograms were generated, dividing the patients into four groups: high (>50 Gy) thyroid and pituitary doses ( HTHP group); high thyroid and low pituitary doses ( HTLP group); low thyroid and high pituitary doses; and low thyroid and pituitary doses. Incidence of hypothyroidism was analysed. Results Twenty-two (34%) and 17 patients (26%) received high mean thyroid and pituitary doses, respectively. At 18 months, 23.1% of patients manifested various types of hypothyroidism. The HTHP group showed the highest incidence (83.3%) of hypothyroidism, followed by the HTLP group (50%). Conclusions NPC patients with high thyroid and pituitary gland doses carried the highest risk of abnormal thyroid physiology. The dose to the thyroid was more influential than the pituitary dose at 18 months after radiotherapy, and therefore more attention should be given to the thyroid gland in radiotherapy planning. [ABSTRACT FROM AUTHOR]

Abstract: Background and purpose: Significant tumor shrinkage and weight loss may occur during Intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC). This study aims to evaluate the dosimetric effect of volumetric changes on target volumes and organs at risk (OARs) during IMRT, using reassessment of computed tomography (CT) and magnetic resonance imaging (MRI). Material and methods: Nineteen loco-regionally advanced NPC patients treated with IMRT were recruited prospectively. Repeat planning CT and MRI were acquired at 30 and 50Gy intervals. Recontouring of target volumes and OARs was based on the fused CT-MRI images. Hybrid plans with recontouring were generated. The assessment of volumetric and dosimetric changes was performed by comparing the hybrid plans with the original plan. Results: There was volume reduction of target volumes and parotid glands over the course of IMRT. Relative to the original plan, the hybrid plans demonstrated significantly higher dose to most of target volumes with greater dose inhomogeneity, higher maximum doses to the spinal cord and brainstem, and higher median doses to the parotid glands. Conclusions: Replanning with repeat CT and MRI scans at 30Gy is essential to keep a satisfactory dose to the target volumes and avoid overdosing the OARs. [Copyright &y& Elsevier]

Abstract: This study compared the oral cavity dose between the routine 7-beam intensity-modulated radiotherapy (IMRT) beam arrangement and 2 other 7-beam IMRT with the conventional radiotherapy beam arrangements in the treatment of nasopharyngeal carcinoma (NPC). Ten NPC patients treated by the 7-beam routine IMRT technique (IMRT-7R) between April 2009 and June 2009 were recruited. Using the same computed tomography data, target information, and dose constraints for all the contoured structures, 2 IMRT plans with alternative beam arrangements (IMRT-7M and IMRT-7P) by avoiding the anterior facial beam and 1 conventional radiotherapy plan (CONRT) were computed using the Pinnacle treatment planning system. Dose-volume histograms were generated for the planning target volumes (PTVs) and oral cavity from which the dose parameters and the conformity index of the PTV were recorded for dosimetric comparisons among the plans with different beam arrangements. The dose distributions to the PTVs were similar among the 3 IMRT beam arrangements, whereas the differences were significant between IMRT-7R and CONRT plans. For the oral cavity dose, the 3 IMRT beam arrangements did not show significant difference. Compared with IMRT-7R, CONRT plan showed a significantly lower mean dose, V30 and V-40, whereas the V-60 was significantly higher. The 2 suggested alternative beam arrangements did not significantly reduce the oral cavity dose. The impact of varying the beam angles in IMRT of NPC did not give noticeable effect on the target and oral cavity. Compared with IMRT, the 2-D conventional radiotherapy irradiated a greater high-dose volume in the oral cavity. [Copyright &y& Elsevier]

Abstract: Adaptive radiotherapy (ART) has been introduced to correct the radiation-induced anatomic changes in head and neck cases during a treatment course. This study evaluated the potential dosimetric benefits of applying a 3-phase adaptive radiotherapy protocol in nasopharyngeal carcinoma (NPC) patients compared with the nonadaptive single-phase treatment protocol. Ten NPC patients previously treated with this 3-phase radiation protocol using Hi-Art Tomotherapy were recruited. Two new plans, PII-ART and PIII-ART, were generated based on the up-to-date computed tomography (CT) images and contours and were used for treatment in phase two (PII; after 25th fraction) and phase three (PIII; after 35th fraction), respectively. To simulate the situation of no replanning, 2 hybrid plans denoted as PII-NART and PIII-NART were generated using the original contours pasted on the PII- and PIII-CT sets by CT-CT fusion. Dosimetric comparisons were made between the NART plans and the corresponding ART plans. In both PII- and PIII-NART plans, the doses to 95% of all the target volumes (D95) were increased with better dose uniformity, whereas the organs at risk (OARs) received higher doses compared with the corresponding ART plans. Without replanning, the total dose to 1% of brainstem and spinal cord (D1) significantly increased 7.87 ± 7.26% and 10.69 ± 6.72%, respectively (P = 0.011 and 0.001, respectively), in which 3 patients would have these structures overdosed when compared with those with two replannings. The total maximum doses to the optic chiasm and pituitary gland and the mean doses to the left and right parotid glands were increased by 10.50 ± 10.51%, 8.59 ± 6.10%, 3.03 ± 4.48%, and 2.24 ± 3.11%, respectively (P = 0.014, 0.003, 0.053, and 0.046, respectively). The 3-phase radiotherapy protocol showed improved dosimetric results to the critical structures while keeping satisfactory target dose coverage, which demonstrated the advantages of ART in helical tomotherapy of NPC. [Copyright &y& Elsevier]

Purpose: Locally recurrent nasopharyngeal carcinoma (NPC) patients can be salvaged by reirradiation with a substantial degree of radiation-related complications. Stereotactic radiotherapy (SRT) is widely used in this regard because of its rapid dose falloff and high geometric precision. The aim of this study was to examine whether the newly developed intensity-modulated stereotactic radiotherapy (IMSRT) has any dosimetric advantages over three other stereotactic techniques, including circular arc (CARC), static conformal beam (SmMLC), and dynamic conformal arc (mARC), in treating locally recurrent NPC. Methods and Materials: Computed tomography images of 32 patients with locally recurrent NPC, previously treated with SRT, were retrieved from the stereotactic planning system for contouring and computing treatment plans. Treatment planning of each patient was performed for the four treatment techniques: CARC, SmMLC, mARC, and IMSRT. The conformity index (CI) and homogeneity index (HI) of the planning target volume (PTV) and doses to the organs at risk (OARs) and normal tissue were compared. Results: All four techniques delivered adequate doses to the PTV. IMSRT, SmMLC, and mARC delivered reasonably conformal and homogenous dose to the PTV (CI <1.47, HI <0.53), but not for CARC (p < 0.05). IMSRT presented with the smallest CI (1.37) and HI (0.40). Among the four techniques, IMSRT spared the greatest number of OARs, namely brainstem, temporal lobes, optic chiasm, and optic nerve, and had the smallest normal tissue volume in the low-dose region. Conclusion: Based on the dosimetric comparison, IMSRT was optimal for locally recurrent NPC by delivering a conformal and homogenous dose to the PTV while sparing OARs. [ABSTRACT FROM AUTHOR]