Survey
* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Journal of Medical Imaging and Radiation Oncology 58 (2014) 18–24 bs_bs_banner RADIOLO GY —O R I G I N AL A R T I C L E Head and neck squamous cell cancer (stages III and IV) induction chemotherapy assessment: Value of FDG volumetric imaging parameters Jielin Yu,1 Timothy Cooley,2 Minh-Tam Truong,3 Gustavo Mercier1 and Rathan M. Subramaniam1,3* 1 Department of Radiology, 2Medical Oncology, 3Radiation Oncology, Boston University School of Medicine, Boston, Massachusetts, USA J Yu; T Cooley MD; M-T Truong MD; G Mercier MD, PhD; RM Subramaniam MD, PhD, MPH. Correspondence A/Prof. Rathan Subramaniam, Division of Nuclear Medicine, Russel H Morgan Department of Radiology and Radiology Science, Johns Hopkins Medical Institutions, 601 N. Caroline Street/JHOC 3235, Baltimore MD 21287, USA. Email: [email protected] *Present address: Russel H Morgan Department of Radiology and Radiological Sciences, Johns Hopkins Medical Institutions, Baltimore, MD, USA. Submitted 4 February 2013; accepted 30 April 2013. doi:10.1111/1754-9485.12081 Abstract Introduction: To evaluate whether the change in the metabolic tumour volume (MTV) or total lesion glycolysis (TLG) of the primary tumour, before and after induction chemotherapy, predicts outcome for patients with advanced head and neck squamous cell cancer (SCC). Methods: Twenty-eight patients with advanced (American Joint Committee on Cancer stage III and IV) head and neck SCC who underwent positron emission tomography (PET)/CT were included in this retrospective study. Primary tumour MTV and TLG were measured using gradient and fixed percentage threshold segmentations. Outcome endpoint was disease progression or mortality. Pearson correlation, Bland–Altman and receiver operator characteristic analysis were performed. Results: The Pearson’s correlation coefficients between percentage changes (pre- and post-induction chemotherapy) from gradient MTV (MTVG) and the 38% SUVmax threshold MTV (MTV38) was 0.96 and between MTVG and the 50% threshold MTV (MTV50) was 0.95 (P < 0.0001). The corresponding Pearson r between TLGG and TLG38 was 0.94 and between TLGG and TLG50 was 0.96 (P < 0.0001). The least bias was 1.89% (standard deviation = 25.30%) between the percentage changes of MTVG and MTV50. The areas under the curve for predicting progression or mortality were 0.76 (P = 0.03) for MTVG and 0.82 for TLGG (P = 0.009). Optimum cut points of a 42% reduction in MTVG and a 55% reduction in the TLGG predict event-free survival with a sensitivity of 62.5% and a specificity of 90% and a hazards ratio of 6.25. Conclusion: A reduction in primary tumour MTV of at least 42% or in TLG of at least 55% after induction chemotherapy may predict event-free survival in patients with advanced head and neck SCC. Key words: head and neck; PET/CT. Introduction Induction chemotherapy is an emerging treatment paradigm for treating inoperable locally advanced squamous cell carcinomas of the head and neck.1 Induction chemotherapy followed by chemoradiotherapy is a form of treatment intensification and is evolving. This may contribute to a better survival rate compared with chemoradiotherapy alone.2 Monitoring the response to induction chemotherapy provides critical information that allows physicians to triage to the best post-induction treatment. 18 Fluorodeoxyglucose positron emission tomography/ computed tomography (FDG PET/CT) has proven to be clinically useful as a diagnostic, staging and therapy planning tool.3–7 The role of FDG PET/CT in determining the outcome of induction chemotherapy has been explored. Previous studies indicate that PET/CT shows a significant correlation with pathological response following induction and concurrent chemoradiotherapy (CCRT).8 It has been shown to have the same efficacy as endoscopy with biopsy for determining the tumour volume after induction therapy.9 © 2013 The Royal Australian and New Zealand College of Radiologists PET volumetric parameters and HNSCC The purpose of this exploratory study is to evaluate whether the change in the metabolic tumour volume (MTV) and total lesion glycolysis (TLG) of the primary tumour, before and after induction chemotherapy, predicts outcome of patients with locally advanced head and neck cancer. Methodology Patients and study design This is a single-institution retrospective study and was approved by the Institutional Review Board. Informed consent requirements were waived for this study. All 28 patients, with biopsy-proven head and neck squamous cell carcinoma who underwent a FDG PET/CT at baseline and post-induction chemotherapy from January 2010 to April 2011 in our institution, were included in the study. All the patients were treated with induction chemotherapy followed by CCRT. The induction chemotherapy regimen consisted of three cycles of Taxotere (docetaxol), cisplatin and 5-fluorouricil (TPF), with minor adjustments for toxicity and other complications. Postinduction therapy consisted of 6 to 7 weeks of CCRT, with 69.96 Gy over 33 fractions. PET/CT All PET/CT studies were performed on a GE Discovery STE 16 (General Electric, Milwaukee, WI, USA) PET/CT scanner according to the institutional standard clinical protocol. For all patients, a dedicated head and neck protocol was instituted. Patients were scanned from skull base to aortic arch with the arms down and then clavicle to mid thigh with the arms up. The average patient blood glucose level was 103 mg/dl (standard deviation (SD) 21 mg/dL). Patients were injected with an average of 11.3 mCi (SD 0.6 mCi) or 418.1 Mbq (SD 22.2 Mbq) of 18F-FDG and incubated for an average period of 65 min (SD 7 min). The dedicated head and neck imaging protocol consisted of two-dimensional PET scans obtained from the skull base to the arch of the aorta with a 30-cm field of view and 128 ¥ 128 matrix.10 The emission scan lasted for 5 min per bed position. The remainder of the body (down to the mid thighs) was imaged using a weightbased emission scan time per bed position. PET slice thickness was 3.27 mm. Helical (16 detector) CT images were obtained with a matrix of 512 ¥ 512. Beam collimation was 10 mm with a pitch of 0.984. Table speed was 9.84 mm/rotation, and the slice thickness was 0.625 mm. KV of 120 and mAs of 440 were used. CT images were reconstructed using a slice thickness of 3.75 mm every 3.27 mm. In addition, CT images were reconstructed using a slice thickness of 1.25 mm every 1.25 mm in soft tissue and a bone algorithm to generate a diagnostic level CT of the neck for review. PET/CT © 2013 The Royal Australian and New Zealand College of Radiologists studies were performed at baseline before the start of induction chemotherapy and 2 to 3 weeks after the completion of induction chemotherapy. Image analysis All PET/CT studies were retrieved from the electronic archival system and reviewed on a MIMvista workstation (software version 4.1, MIM Software Inc., Cleveland, OH, USA) by a board certified radiologist with nuclear radiology and neuroradiology faculty member with 3 years experience as a faculty and head and neck and PET/CT imaging. PET, CT and fused PET/CT images were reviewed in axial, coronal and sagittal planes. For the purposes of this study, the relevant imaging biomarker measurements were MTV and TLG from PET. MTV was defined as the tumour volume with FDG uptake segmented by a gradient-based method and fixed threshold methods at 38% and 50% of SUVmax. The TLG was defined as (MTV) x (SUVmean). The commercially available MIMvista software analysis suite (MIM Software Inc.) includes a contouring suite for radiation therapy planning and a PET/CT fusion suite. The edges of the primary tumour were automatically calculated and outlined in both segmentation methods. Once the primary tumour was segmented, MTV and TLG were semiautomatically calculated by the MIMvista software. Because there is greater intrareader variability measuring the FDG volumentric parameters (MTV and TLG) for smaller volume tumour,11 we did not segment the nodal metastasis. In addition, previous studies have demonstrated primary tumour volume than nodal volume as predictors of outcome.12 For these reasons, we only segmented the primary tumours. Segmentation methods (a) Gradient segmentation method Gradient segmentation of tumour volume identifies the tumour on the basis of a change in count level at the tumour border. Complex segmentation methods have been proposed including denoising, deblurring, gradient estimation and watershed transformation. The gradient segmentation method used in MIMvista (version 4.1) has been previously described,13,14 and is simple and easy to use. It calculates spatial derivatives along the tumour radii and then defines the tumour edge on the basis of derivative levels and continuity of the tumour edge. The software relies on an operator-defined starting point near the centre of the lesion. As the operator drags the cursor from the centre of the lesion, six axes extend out, providing visual feedback for the starting point of gradient segmentation. Spatial gradients are calculated along each axis interactively, and the length of an axis is restricted when a large spatial gradient is detected. The six axes define an ellipsoid that is then used as an initial 19 J Yu et al. bounding region for gradient detection. The reader can add regions until visually satisfied that the entire primary tumour is included in the contour. Inc., Chicago, IL, USA) statistical packages for all analyses, and all hypothesis tests are two-sided with a significance level of 0.05. (b) Fixed percent threshold segmentation method Results The fixed SUVmax threshold contouring method relies on including all voxels that are greater than a defined percent of the maximum voxel within an operatordefined sphere (in this study 38% and 50% of SUVmax). We used these fixed threshold as have been used in previous studies.15 Cross-sectional circles are displayed in all three projections (axial, sagittal and coronal) to ensure three-dimensional coverage of the primary tumour.13 Patients The mean age of the patients was 59 years (range, 29–82 years). The primary tumour sites were oral cavity and oropharynx (n = 14), larynx (n = 5), hypopharynx (n = 5) and other (n = 4). The distribution of patients by the American Joint Committee on Cancer (6th edition) stage of the cancers included stages III (n = 3, 10.7%), IVA (n = 20, 71.4%), IVB (n = 4, 14.3%) and IVC (n = 1, 3.6%). The mean follow-up period for the patients was 11 months (range, 2–26 months). Patient characteristics and therapy details are summarized in Table 1. Outcome endpoints The primary outcome measure is to establish whether the change in exploratory imaging markers, MTV and TLG, before and after induction chemotherapy, predicts overall survival and progression-free survival (PFS). Overall survival is defined as the time from initiation of therapy to death or to the most recent follow-up. Progression-free survival is defined as the time from initiation of therapy to the first documented progression at the primary site, at regional nodes, or at distant metastatic sites. Death from the primary cancer without a documented site of recurrence or progression or death from an unknown cause is considered death from local regional disease. Electronic medical records, imaging records and office visits at our institution were used to establish the overall survival and PFS. Outcome measures of the study were PFS or disease progression/ mortality. The median follow-up time was 12.5 months. The Pearson correlation coefficient between the percentage changes (before and after induction chemotherapy) in gradient MTV (MTVG) and 38% SUVmax threshold MTV (MTV38) was 0.96 (P < 0.0001). The Pearson r between MTVG and 50% SUVmax threshold MTV (MTV50) was 0.95 (P < 0.0001). The corresponding Pearson r between TLGG and TLG38 was 0.94 (P < 0.0001) and 0.96 (P < 0.0001) between TLGG and TLG50. The Bland–Altman analysis showed a bias of 4.48% (SD = 26.13%) between the percentage changes of MTVG and MTV38. The corresponding bias was 1.89% (SD = 25.30%) between the percentage changes of MTVG and MTV50. The corresponding biases for TLG were 6.51% (SD = 28.96%) and 5.63% (SD = 32.92%). Statistical methods Table 1. Patient characteristics We present our summary statistics as the mean ⫾SD or range for continuous variables, or frequency and percentage for categorical variables. We used the Pearson correlation coefficient to establish the relationship between different segmentation methods, and we used Bland–Altman analysis between the two best-correlated segmentation methods to establish the reliability of the methods for measuring changes in MTV and TLG. The baseline MTV or TLG was used as the denominator for the calculation of percentage reduction. Between group analysis was performed using the Mann–Whitney U-test. Receiver operating characteristic (ROC) analysis was used to determine area under the curve (AUC) to estimate the accuracy and predictive ability of MTV and TLG. The optimum cut points were established to predict event-free survival. We used the Prism 5 (GraphPad Software Inc., San Diego, CA, USA) and SPSS 19 (SPSS 20 Volumetric and metabolic changes and segmentation methods Characteristic Age, mean (range) Sex Male Female Primary tumour site Oral cavity/oropharynx Larynx Hypopharynx Other sites AJCC stage III IV Completed three cycles of induction chemotherapy Yes No Follow-up time, mean (range) No. patients (%) n = 28 59 (29–82) 20 (71.43%) 8 (28.57%) 14 (50.0%) 5 (17.9%) 5 (17.9%) 4 (14.2%) 3 (10.7%) 25 (89.3%) 20 (71.43%) 8 (28.57%) 11 (2–26) © 2013 The Royal Australian and New Zealand College of Radiologists PET volumetric parameters and HNSCC Fig. 1. Pre- and post-induction chemotherapy change of metabolic tumour volume (MTV) (gradient segmentation) for patients who survived without an event and for patients who progressed or died. SUVmax changes and outcomes The median SUVmax changes for patients who had no events and for patients who had progressed or died were 100% (IQR 53.5% to 100%) and 51.88% (IQR 19.07% to 93.88%), respectively (Mann–Whitney U-test P = 0.09). In the ROC analysis, the AUC for SUVmax was 0.70 (95% CI 0.47–0.92; P = 0.10). were 0.84 (95% CI 0.66–1.00; P = 0.006) and 0.84 (95% CI 0.65–1.00; P = 0.006). An optimum cut point of 55% reduction in the TLGG predicts event-free survival with a sensitivity of 62.5% and a specificity of 90% and a HR of 6.25. The corresponding cut point for TLG50 was 59% reduction with the same sensitivity, specificity and HR. Discussion MTV changes and outcomes The median MTVG changes for patients who had no events and for patients who had progressed or died were 100% (IQR 88.6% to 100%) and 36.75% (IQR -55.19% to 89.13%), respectively (Mann–Whitney U-test P = 0.02) (Figs 1,2). The corresponding values using MTV38 were 100% (IQR 84.1% to 100%) and 19.05% (IQR -44.1 to 81.62); and for MTV50 100% (IQR 84.85% to 100%) and 24.04% (IQR -17.25% to 77.78%). There was a significant difference between the two groups for both MTV38 (P = 0.02) and MTV50 (P = 0.02). In the ROC analysis, the AUC for MTVG was 0.76 (95% CI 0.55–0.97; P = 0.03) (Fig. 3). AUCs for MTV38 and MTV50 were 0.77 (95% CI 0.56–0.98; P = 0.03) and 0.76 (95% CI 0.55–0.98; P = 0.03). An optimum cut point of 42% reduction in the MTVG predicts event-free survival with a sensitivity of 67% and a specificity of 90% and an hazards ratio (HR) of 6.3. The corresponding cut point for MTV50 was a 53% reduction with the same sensitivity, specificity and HR. TLG changes and outcome The median TLGG changes for patients who had no events, and for patients who had progressed or died were 100% (IQR 93.23% to 100%) and 43.16% (IQR -55.47% to 88.96%), respectively (P = 0.007) (Fig. 4). The corresponding values using TLG38 were 100% (IQR 94.34% to 100%) and 21.52% (IQR -23.66% to 85.31%) (P = 0.004); for TLG50 99.02% (IQR 40.41% to 100%) and 41.96% (IQR -21.98% to 84.68%) (P = 0.006). In the ROC analysis, AUC for TLGG was 0.82 (95% CI 0.64–1.00; P = 0.009) (Fig. 3). AUCs for TLG38 and TLG50 © 2013 The Royal Australian and New Zealand College of Radiologists The aim of this exploratory study was to determine whether metabolic volumetric analysis of tumours before and after induction chemotherapy can predict the eventfree survival of head and neck cancer patients. The results suggest that there is a significant difference in the changes of both MTV and TLG between patients who had progressed or died and those who had an event-free survival. Using ROC analysis, a 42% reduction in MTVG or 55% reduction in TLGG were determined to be optimal for predicting event-free survival. The AUCs for MTV50, TLGG, and TLG50 were also determined and found to be similar to MTVG. In addition, the changes in percentage of metabolic volume segmented by gradient and by the fixed percentage threshold methods are highly correlated. Several parameters have been utilized for response assessments. One conventional method is based on changes in the longest measured diameter of the tumour. The maximum diameter approach suffers from a relatively small degree of interobserver reliability.16,17 Additionally, the tumour diameter is only a unidimensional anatomical parameter and provides no metabolic or functional information about the tumour biology. A more functional metabolic parameter is the maximum SUV (SUVmax), the pixel with the highest intensity in the tumour region. Compared with tumour diameter, SUVmax has significantly less interobserver and intraobserver variability.17,18 However, several factors can affect the SUVmax and may under- or overestimate the degree to which it depends on tumour size and the tumour-tobackground ratio.19 The utility of SUVmax as a prognostic factor has been explored with mixed results. With nonsmall-cell lung cancers and head and neck nonsquamous cell carcinomas, using SUVmax values has been 21 J Yu et al. Fig. 2. (a and d) Axial positron emission tomography (PET), (b and e) axial PET/CT and (c and f) coronal PET/CT of a 78-year-old woman with T3N2cM0 stage IVA squamous cell cancer of the oropharynx. Pre-induction chemotherapy primary tumour MTV (gradient segmentation) is 8.3 mL. Induction therapy consisted of three cycles of Taxotere (docetaxol), cisplatin and 5-fluorouracil. The post-induction primary tumour metabolic tumour volume is 6.6 mL (20% reduction). Patient had progressed 4 months after the completion of treatment and died 21 months after treatment. shown to have predictive value.20,21 Other studies, however, have indicated that SUV measurements are not significant or reliable prognostic factors.22,23 In light of the shortcomings of tumour diameter and SUVmax, a new method of assessing prognosis based on volumetric analysis has been drawing increased atten- tion. In the case of small-cell lung cancers, the MTV has been demonstrated to be a significant predictor of patient outcome.24 MTV has also been shown to be an important independent predictor of disease-free survival in the case of oesophageal cancer as well as head and neck cancers.25,26 It has been suggested to add value to Fig. 3. Metabolic tumour volume (MTV) and total lesion glycolysis (TLG) (gradient segmentation) percentage change (pre- and post-therapy) receiver operating characteristic analysis for event-free survival. AUC, area under the curve. 22 © 2013 The Royal Australian and New Zealand College of Radiologists PET volumetric parameters and HNSCC Fig. 4. Pre- and post-induction chemotherapy change of total lesion glycolysis (TLG) (gradient segmentation) for patients who survived without an event and for patients who progressed or died. staging in predicting prognosis of patients with oral and oral cavity squamous cell cancers.14 Our results further demonstrate that MTV and TLG can potentially be used for induction therapy assessment in head and neck squamous cell cancer. In contrary to a prior study,27 we used the same threshold cut points, 38% and 50% of the measured SUVmax in the baseline and then in the postinduction images, as the SUVmax of the primary tumour are likely to change with induction chemotherapy. Our study showed there is significant reduction in the threshold MTV and TLG, after induction chemotherapy, in those who had an event and those who did not. This may be due to lack of radiation inflammation in our study. We did not use the baseline SUVmax for threshold cut point in the post-induction images, as used by a prior study,28 as SUVmax changes with induction therapy. Our results need to be interpreted in the context of our study design. This is an exploratory study with a small number of patients, and the MTV and TLG were segmented using single vendor-provided, FDA-approved, commercially available software. Segmentation of small residual tumours may not be accurate, especially when the tumour volume is less than 10 mL. We did not perform the analysis for nodal disease, as small volume disease have more variability in measurements but acknowledge nodal disease is an important prognostic factor. Though our study only included patients with advanced head and neck cancer (stage III and stage IV) patients, we did not perform Human Papilloma Virus (HPV) status routinely in all head and neck patients at the time of this study. Hence, HPV status is not included in the analysis, which may influence the outcome of some of the patients included in the study. Due to the small sample size, we included both oral cavity and oropharynx in the study. Our follow-up period is limited with a range of 2–26 months with an actuarial median follow-up of 11 months. Conclusion Our exploratory results suggest that a reduction in MTV or TLG of 42% and 55%, respectively, before and after induction chemotherapy, predicts short-term event-free survival in patients with advanced head and neck squa© 2013 The Royal Australian and New Zealand College of Radiologists mous cell cancer (stages III and IV). These exploratory metabolic volumetric imaging parameters and cut points for predicting short to intermediate term outcome need validation in a larger and prospective study, which would include other important clinical parameter such as HPV status. Acknowledgements Rathan Subramaniam was supported by a GE-AUR Research fellowship and received Siemens molecular imaging and MJ Fox foundation research grants and research support from MIM Software Inc.. He is a speaker and consultant for Eli Lilly (Alzheimer’s disease). References 1. Pointreau Y, Atean I, Fayette J, Calais G, Lefebvre JL. Induction chemotherapy in head and neck cancer: a new paradigm. Anticancer Drugs 2011; 22: 613–20. 2. Bardet E, Bourhis J, Cals L et al. [Locally advanced head and neck cancers: recommendations of an expert panel and perspectives for the use of TPF regimen (docetaxel, cisplatin and fluoro-uracil) as induction therapy]. Bull Cancer 2009; 96: 1013–28. 3. Dibble EH, Alvarez AC, Truong MT, Mercier G, Cook EF, Subramaniam RM. 18F-FDG metabolic tumor volume and total glycolytic activity of oral cavity and oropharyngeal squamous cell cancer: adding value to clinical staging. J Nucl Med 2012; 53: 709–15. 4. Subramaniam RM, Wilcox B, Aubry MC, Jett J, Peller PJ. 18F-fluoro-2-deoxy-D-glucose positron emission tomography and positron emission tomography/computed tomography imaging of malignant pleural mesothelioma. J Med Imaging. Radiat Oncol 2009; 53: 160–9. quiz 70. 5. Karantanis D, O’Neill BP, Subramaniam RM et al. Contribution of F-18 FDG PET-CT in the detection of systemic spread of primary central nervous system lymphoma. Clin Nucl Med 2007; 32: 271–4. 6. Hillner BE, Siegel BA, Liu D et al. Impact of positron emission tomography/computed tomography and positron emission tomography (PET) alone on expected management of patients with cancer: initial results from the National Oncologic PET Registry. J Clin Oncol 2008; 26: 2155–61. 23 J Yu et al. 7. Subramaniam RM, Clayton AC, Karantanis D, Collins DA. Hibernoma: 18F FDG PET/CT imaging. J Thorac Oncol 2007; 2: 569–70. 8. Kikuchi M, Shinohara S, Nakamoto Y et al. Sequential FDG-PET/CT after neoadjuvant chemotherapy is a predictor of histopathologic response in patients with head and neck squamous cell carcinoma. Mol Imaging Biol 2011; 13: 368–77. 9. Chepeha DB, Sacco AG, Oxford LE et al. Advanced squamous cell carcinoma of the oropharynx: efficacy of positron emission tomography and computed tomography for determining primary tumor response during induction chemotherapy. Head Neck 2009; 31: 452–60. 10. Subramaniam RM, Truong M, Peller P, Sakai O, Mercier G. Fluorodeoxyglucose-positron-emission tomography imaging of head and neck squamous cell cancer. AJNR Am J Neuroradiol 2010; 31: 598–604. 11. Shah B, Srivastava N, Hirsch AE, Mercier G, Subramaniam RM. Intra-reader reliability of FDG PET volumetric tumor parameters: effects of primary tumor size and segmentation methods. Ann Nucl Med 2012; 26: 707–14. 12. Romesser PB, Qureshi MM, Subramaniam RM, Sakai O, Jalisi S, Truong MT. A Prognostic Volumetric Threshold of Gross Tumor Volume in Head and Neck Cancer Patients Treated With Radiotherapy. Am J Clin Oncol 2012; PMID: 23211218. [Epub ahead of print]. 13. Werner-Wasik M, Nelson AD, Choi W et al. What is the best way to contour lung tumors on PET scans? Multiobserver validation of a gradient-based method using a NSCLC digital PET phantom. Int J Radiat Oncol Biol Phys 2012; 82: 1164–71. 14. Dibble E, Lara Alvarez A, Truong M, Mercier G, Cook E, Subramaniam R. FDG Metabolic tumor volume and total glycolytic activity: prognostic imaging biomarkers of oral and oropharyngeal squamous cell cancers. J Nucl Med 2012; 53: 709–15. 15. Abd El-Hafez YG, Moustafa HM, Khalil HF, Liao CT, Yen TC. Total lesion glycolysis: a possible new prognostic parameter in oral cavity squamous cell carcinoma. Oral Oncol 2013; 49: 261–8. 16. Huang YE, Chen CF, Huang YJ, Konda SD, Appelbaum DE, Pu Y. Interobserver variability among measurements of the maximum and mean standardized uptake values on (18)F-FDG PET/CT and measurements of tumor size on diagnostic CT in patients with pulmonary tumors. Acta Radiol 2010; 51: 782–8. 17. Jackson T, Chung M, Ozonoff A, Mercier G, Subramaniam R. FDG PET/CT inter-observer agreement in head and neck cancer: FDG and CT 24 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. measurements of the primary tumor site. Nucl Med Commun 2012; 33: 305–12. Jacene HA, Leboulleux S, Baba S et al. Assessment of Interobserver Reproducibility in Quantitative 18F-FDG PET and CT Measurements of Tumor Response to Therapy. J Nucl Med 2009; 50: 1760–9. Boellaard R, Krak NC, Hoekstra OS, Lammertsma AA. Effects of noise, image resolution, and ROI definition on the accuracy of standard uptake values: a simulation study. J Nucl Med 2004; 45: 1519–27. Imsande HM, Davison JM, Truong MT et al. Use of 18F-FDG PET/CT as a Predictive Biomarker of Outcome in Patients With Head-and-Neck Non-Squamous Cell Carcinoma. AJR Am J Roentgenol 2011; 197: 976–80. Huang W, Zhou T, Ma L et al. Standard uptake value and metabolic tumor volume of (1)F-FDG PET/CT predict short-term outcome early in the course of chemoradiotherapy in advanced non-small cell lung cancer. Eur J Nucl Med Mol Imaging 2011; 38: 1628–35. Hatt M, Visvikis D, Albarghach NM, Tixier F, Pradier O, Cheze-le Rest C. Prognostic value of 18F-FDG PET image-based parameters in oesophageal cancer and impact of tumour delineation methodology. Eur J Nucl Med Mol Imaging 2011; 38: 1191–202. Tylski P, Stute S, Grotus N et al. Comparative assessment of methods for estimating tumor volume and standardized uptake value in (18)F-FDG PET. J Nucl Med 2010; 51: 268–76. Liao S, Penney BC, Wroblewski K et al. Prognostic value of metabolic tumor burden on 18F-FDG PET in nonsurgical patients with non-small cell lung cancer. Eur J Nucl Med Mol Imaging 2012; 39: 27–38. Tang C, Murphy JD, Khong B et al. Validation that Metabolic Tumor Volume Predicts Outcome in Head-and-Neck Cancer. Int J Radiat Oncol Biol Phys 2012; 83: 1514–20. Hyun SH, Choi JY, Shim YM et al. Prognostic value of metabolic tumor volume measured by 18F-fluorodeoxyglucose positron emission tomography in patients with esophageal carcinoma. Ann Surg Oncol 2010; 17: 115–22. Moule RN, Kayani I, Moinuddin SA et al. The potential advantages of (18)FDG PET/CT-based target volume delineation in radiotherapy planning of head and neck cancer. Radiother Oncol 2010; 97: 189–93. Powell C, Schmidt M, Borri M et al. Changes in functional imaging parameters following induction chemotherapy have important implications for individualised patient-based treatment regimens for advanced head and neck cancer. Radiother Oncol 2013; 106: 112–7. © 2013 The Royal Australian and New Zealand College of Radiologists