[Show abstract][Hide abstract] ABSTRACT: Purpose:
The aim of this work was to compare and validate various computed tomography (CT) number calibration techniques with respect to cone beam CT (CBCT) dose calculation accuracy.
CBCT dose calculation accuracy was assessed for pelvic, lung, and head and neck (H&N) treatment sites for two approaches: (1) physics-based scatter correction methods (CBCTr); (2) density override approaches including assigning water density to the entire CBCT (W), assignment of either water or bone density (WB), and assignment of either water or lung density (WL). Methods for CBCT density assignment within a commercially available treatment planning system (RSauto), where CBCT voxels are binned into six density levels, were assessed and validated. Dose-difference maps and dose-volume statistics were used to compare the CBCT dose distributions with the ground truth of a planning CT acquired the same day as the CBCT.
For pelvic cases, all CTN calibration methods resulted in average dose-volume deviations below 1.5 %. RSauto provided larger than average errors for pelvic treatments for patients with large amounts of adipose tissue. For H&N cases, all CTN calibration methods resulted in average dose-volume differences below 1.0 % with CBCTr (0.5 %) and RSauto (0.6 %) performing best. For lung cases, WL and RSauto methods generated dose distributions most similar to the ground truth.
The RSauto density override approach is an attractive option for CTN adjustments for a variety of anatomical sites. RSauto methods were validated, resulting in dose calculations that were consistent with those calculated on diagnostic-quality CT images, for CBCT images acquired of the lung, for patients receiving pelvic RT in cases without excess adipose tissue, and for H&N cases.
Strahlentherapie und Onkologie 09/2015; 191(12). DOI:10.1007/s00066-015-0890-7 · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose:
To describe a methodology, based on cluster analysis, to partition multi-parametric functional imaging data into groups (or clusters) of similar functional characteristics, with the aim of characterizing functional heterogeneity within head and neck tumour volumes. To evaluate the performance of the proposed approach on a set of longitudinal MRI data, analysing the evolution of the obtained sub-sets with treatment.
Material and methods:
The cluster analysis workflow was applied to a combination of dynamic contrast-enhanced and diffusion-weighted imaging MRI data from a cohort of squamous cell carcinoma of the head and neck patients. Cumulative distributions of voxels, containing pre and post-treatment data and including both primary tumours and lymph nodes, were partitioned into k clusters (k = 2, 3 or 4). Principal component analysis and cluster validation were employed to investigate data composition and to independently determine the optimal number of clusters. The evolution of the resulting sub-regions with induction chemotherapy treatment was assessed relative to the number of clusters.
The clustering algorithm was able to separate clusters which significantly reduced in voxel number following induction chemotherapy from clusters with a non-significant reduction. Partitioning with the optimal number of clusters (k = 4), determined with cluster validation, produced the best separation between reducing and non-reducing clusters.
The proposed methodology was able to identify tumour sub-regions with distinct functional properties, independently separating clusters which were affected differently by treatment. This work demonstrates that unsupervised cluster analysis, with no prior knowledge of the data, can be employed to provide a multi-parametric characterization of functional heterogeneity within tumour volumes.
PLoS ONE 09/2015; 10(9):e0138545. DOI:10.1371/journal.pone.0138545 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose The study aimed to apply the atlas of complication incidence (ACI) method to patients receiving radical treatment for head and neck squamous cell carcinomas (HNSCC), to generate constraints based on dose-volume histograms (DVHs), and to identify clinical and dosimetric parameters that predict the risk of grade 3 oral mucositis (g3OM) and pharyngeal dysphagia (g3PD). Methods and Materials Oral and pharyngeal mucosal DVHs were generated for 253 patients who received radiation (RT) or chemoradiation (CRT). They were used to produce ACI for g3OM and g3PD. Multivariate analysis (MVA) of the effect of dosimetry, clinical, and patient-related variables was performed using logistic regression and bootstrapping. Receiver operating curve (ROC) analysis was also performed, and the Youden index was used to find volume constraints that discriminated between volumes that predicted for toxicity. Results We derived statistically significant dose-volume constraints for g3OM over the range v28 to v70. Only 3 statistically significant constraints were derived for g3PD v67, v68, and v69. On MVA, mean dose to the oral mucosa predicted for g3OM and concomitant chemotherapy and mean dose to the inferior constrictor (IC) predicted for g3PD. Conclusions We have used the ACI method to evaluate incidences of g3OM and g3PD and ROC analysis to generate constraints to predict g3OM and g3PD derived from entire individual patient DVHs. On MVA, the strongest predictors were radiation dose (for g3OM) and concomitant chemotherapy (for g3PD).
International journal of radiation oncology, biology, physics 07/2015; 93(3). DOI:10.1016/j.ijrobp.2015.07.2263 · 4.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Radical chemo-radiotherapy (CRT) is an effective organ-sparing treatment option for patients with locally advanced head and neck cancer (LAHNC). Despite advances in treatment for LAHNC, a significant minority of these patients continue to fail to achieve complete response with standard CRT. By constructing a multi-modality functional imaging (FI) predictive biomarker for CRT outcome for patients with LAHNC we hope to be able to reliably identify those patients at high risk of failing standard CRT. Such a biomarker would in future enable CRT to be tailored to the specific biological characteristics of each patients' tumour, potentially leading to improved treatment outcomes.
The INSIGHT study is a single-centre, prospective, longitudinal multi-modality imaging study using functional MRI and FDG-PET/CT for patients with LAHNC squamous cell carcinomas receiving radical CRT. Two cohorts of patients are being recruited: one treated with, and another treated without, induction chemotherapy. All patients receive radical intensity modulated radiotherapy with concurrent chemotherapy. Patients undergo functional imaging before, during and 3 months after completion of radiotherapy, as well as at the time of relapse, should that occur within the first two years after treatment. Serum samples are collected from patients at the same time points as the FI scans for analysis of a panel of serum markers of tumour hypoxia.
The primary aim of the INSIGHT study is to acquire a prospective multi-parametric longitudinal data set comprising functional MRI, FDG PET/CT, and serum biomarker data from patients with LAHNC undergoing primary radical CRT. This data set will be used to construct a predictive imaging biomarker for outcome after CRT for LAHNC. This predictive imaging biomarker will be used in future studies of functional imaging based treatment stratification for patients with LAHNC. Additional objectives are: defining the reproducibility of FI parameters; determining robust methods for defining FI based biological target volumes for IMRT planning; creation of a searchable database of functional imaging data for data mining. The INSIGHT study will help to establish the role of FI in the clinical management of LAHNC.
NCRI H&N CSG ID 13860.
[Show abstract][Hide abstract] ABSTRACT: Radical radiotherapy for head and neck cancer (HNC) may deliver significant doses to brain structures. There is evidence that this may cause a decline in neurocognitive function (NCF). Radiation dose to the medial temporal lobes, and particularly to the hippocampi, seems to be critical in determining NCF outcomes. We evaluated the feasibility of two alternative intensity-modulated radiotherapy (IMRT) techniques to generate hippocampus- and brain-sparing HNC treatment plans to preserve NCF.
A planning study was undertaken for ten patients with HNC whose planning target volume (PTV) included the nasopharynx. Patients had been previously treated using standard (chemo)-IMRT techniques. Bilateral hippocampi were delineated according to the RTOG atlas, on T1w MRI co-registered to the RT planning CT. Hippocampus-sparing plans (HSRT), and whole-brain/hippocampus-sparing fixed-field non-coplanar IMRT (BSRT) plans, were generated. DVHs and dose difference maps were used to compare plans. NTCP calculations for NCF impairment, based on hippocampal dosimetry, were performed for all plans.
Significant reductions in hippocampal doses relative to standard plans were achieved in eight of ten cases for both HSRT and BSRT. EQD2 D40% to bilateral hippocampi was significantly reduced from a mean of 23.5 Gy (range 14.5-35.0) in the standard plans to a mean of 8.6 Gy (4.2-24.7) for HSRT (p = 0.001) and a mean of 9.0 Gy (4.3-17.3) for BSRT (p < 0.001). Both HSRT and BSRT resulted in a significant reduction in doses to the whole brain, brain stem, and cerebellum.
We demonstrate that IMRT plans for HNC involving the nasopharynx can be successfully optimised to significantly reduce dose to the bilateral hippocampi and whole brain. The magnitude of the achievable dose reductions results in significant reductions in the probability of radiation-induced NCF decline. These results could readily be translated into a future clinical trial.
PLoS ONE 03/2015; 10(3):e0120141. DOI:10.1371/journal.pone.0120141 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: Studies evaluating the benefit of water swallow tests have focused on their value in identifying patients at risk of aspiration. As well as information on potential aspiration risk, the 100 mL Water Swallow Test (WST) can also be used to measure specific aspects of swallowing performance. The purpose of this study was to understand changes in swallowing capacity and volume in patients recovering from intensity modulated radiotherapy (IMRT) for oropharyngeal cancer.
Methods: The 100 mL WST was administered to 37 patients with oropharyngeal cancer before commencing a course of IMRT at a tertiary cancer center. Patients were then assessed at 3, 6 and 12 months after treatment.
Results: There was a significant reduction in mean swallow volume from baseline to each post-treatment time point: 3 months (p = 0.001), 6 months (p = 0.001) and 12 months (p = 0.02). Equally, significant differences were observed for swallowing capacity from baseline to each timepoint (all p<0.001).
Conclusions: There is a significant reduction in swallow volume and capacity from baseline to 3, 6 and 12 months after treatment. Improvements in mean group scores were observed up to 12 months but did not return to baseline. The 100 mL WST is a valuable adjunct to the clinical swallowing evaluation providing quantitative data to document swallowing recovery after treatment.
[Show abstract][Hide abstract] ABSTRACT: Background
Ipsilateral radiotherapy is an established technique for treating well-lateralised tonsillar tumours. Concerns exist regarding the risk of contralateral nodal failure, particularly in patients with ipsilateral nodal involvement at presentation. In this study, we retrospectively reviewed the clinical outcomes of patients treated with ipsilateral radiotherapy aiming to identify factors that predispose to a higher risk of contralateral nodal recurrence.
Retrospective case note review of all patients with tonsillar cancer who were treated using ipsilateral radiotherapy between September 1995 and September 2011 was performed. Demographics, T and N stage, involvement of soft palate and/or tongue base, presence of extra-capsular spread (ECS) and treatment details were recorded. Kaplan–Meier curves for treatment outcomes were generated.
A total of 136 patients were identified. Median follow-up was 4.2 years. Twelve (9%) patients had loco-regional recurrence. Eight patients (6%) had contralateral recurrence. N2b disease, ECS and number of pack-years of smoking were associated with contralateral nodal recurrence. Five-year overall survival was 89%, loco-regional disease-free survival 90%, disease-free survival 86% and distal recurrence-free survival 96%.
N2b disease, ECS and a greater than 10 pack-year smoking history are risk factors for contralateral nodal recurrence in well-lateralised tonsillar cancers. Prophylactic irradiation of the contralateral neck should be recommended in this group of patients.
[Show abstract][Hide abstract] ABSTRACT: Fatigue during head and neck radiotherapy may be related to radiation dose to the central nervous system (CNS). The impact of patient, tumour, and dosimetric variables on acute fatigue was assessed in nasopharyngeal cancer patients undergoing chemoradiotherapy.
Radiation dose to the following retrospectively-delineated CNS structures; brainstem, cerebellum, pituitary gland, pineal gland, hypothalamus, hippocampus and basal ganglia (BG) and clinical variables were related to incidence of ⩾ grade 2 fatigue in 40 patients.
Sixty per cent of patients reported fatigue during and following radiotherapy. Dmean and D2 to the BG and Dmean to the pituitary gland were significantly associated with fatigue during radiation (P<0.01). Dmean to the cerebellum was associated with fatigue following radiotherapy and at any time (P<0.01). After adjusting for clinical factors, an association remained between fatigue during radiotherapy and mean dose and D2 to the pituitary gland and BG (P=0.012, 0.036, 0.009 and 0.018) and mean dose to the cerebellum following radiation and at any time (P=0.042 and 0.029).
Disruption of connections between BG, cerebellum, and higher cortical centres or disruption of pituitary-regulated hormonal balance may be implicated in the pathophysiology of radiation-related fatigue.
Radiotherapy and Oncology 08/2013; 110(3). DOI:10.1016/j.radonc.2013.06.042 · 4.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
Reovirus exploits aberrant signalling downstream of Ras to mediate tumor-specific oncolysis. Since ~90% squamous cell carcinomas of the head and neck (SCCHN) over-express EGFR and SCCHN cell lines are sensitive to oncolytic reovirus, we conducted a detailed analysis of the effects of reovirus in 15 head and neck cancer cell lines. Both pre- and post-entry events were studied in an attempt to define biomarkers predictive of sensitivity/resistance to reovirus. In particular, we analysed the role of EGFR/Ras signalling in determining virus-mediated cytotoxicity in SCCHN.
To test whether EGFR pathway activity was predictive of increased sensitivity to reovirus, correlative analyses between reoviral IC50 by MTT assay and EGFR levels by western blot and FACS were conducted. Inhibition or stimulation of EGFR signalling were analysed for their effect on reoviral oncolysis by MTT assay, and viral growth by TCID50 assay. We next analysed the effects of inhibiting signalling downstream of Ras, by specific inhibitors of p38MAPK, PI3-K or MEK, on reoviral killing examined by MTT assay. The role of PKR in reoviral killing was also determined by blockade of PKR using 2-aminopurine and assaying for cell survival by MTT assay. The apoptotic response of SCCHN to reovirus was examined by western blot analysis of caspase 3 cleavage.
Correlative analyses between reoviral sensitivity and EGFR levels revealed no association. Intermediate sub-viral and core particles showed the same infectivity/cytotoxicity as intact reovirus. Therefore, sensitivity was not determined by cell entry. In 4 cell lines, oncolysis and viral growth were both unaffected by inhibition or stimulation of EGFR signalling. Inhibition of signalling downstream of Ras did not abrogate reoviral oncolysis and, in addition, modulation of PKR using 2-aminopurine did not alter reovirus sensitivity in resistant cell lines. Caspase 3 cleavage was not detected in infected cells and oncolysis was observed in pan-caspase inhibited cells.
In summary, reovirus is potently oncolytic in a broad panel of SCCHN cell lines. Attempts to define sensitivity/resistance by analysis of the EGFR/Ras/MAPK pathway have failed to provide a clear predictive biomarker of response. Further analysis of material from in vitro and clinical studies is ongoing in an attempt to shed further light on this issue.
BMC Cancer 08/2012; 12(1):368. DOI:10.1186/1471-2407-12-368 · 3.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Irradiation of tumors in the larynx and pharynx is often technically challenging in patients with a short neck or high shoulders. Shoulder retraction devices can sometimes resolve this problem and allow irradiation via lateral beam directions. This study aimed to measure the proportion of patients who would benefit from such an approach and to quantify the magnitude of the benefit obtained. Twenty patients were studied. Simulator images were obtained before and after intervention. The additional exposure of the cervical spine was measured. Patient comfort and acceptability were assessed with a questionnaire. Improvement of exposure of the cervical spine was observed in 80% of patients. In 20%, there was either no difference or the position was worse. Shoulder retraction exposed a mean of 8.4-10.2 mm more of the cervical spine. Patients in general reported the device as comfortable. The use of a shoulder retraction device produced clinically significant improvements in exposure of the tissues of the cervical spine and neck and should be considered in patients being irradiated for tumors arising in the larynx or hypopharynx.
Medical dosimetry: official journal of the American Association of Medical Dosimetrists 02/2012; 37(3):293-5. DOI:10.1016/j.meddos.2011.11.002 · 0.76 Impact Factor