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Longitudinal Characterization of MRI Kinetics in Irradiated Dysphagia-Related Structures for Nasopharyngeal Carcinoma Patients Receiving IMRT
Volume 94 Number 4 2016
224 Longitudinal Characterization of MRI Kinetics in Irradiated Dysphagia-Related Structures for Nasopharyngeal Carcinoma Patients Receiving IMRT J.A. Messer,1 A.S.R. Mohamed,1 K.A. Hutcheson,1 Y. Ding,2 J. Wang,2 H. Eichelberger,3 C. French,3 D.I. Rosenthal,1 G.B. Gunn,2 and C.D. Fuller2; 1The University of Texas MD Anderson Cancer Center, Houston, TX, 2MD Anderson Cancer Center, Houston, TX, 3 The University of Texas Medical School, Houston, TX Purpose/Objective(s): Radiation therapy (RT) for nasopharyngeal carcinoma (NPC) is often effective at curing disease but can injure the surrounding organs at risk, including the muscles responsible for swallowing, with possible resultant short-term or long-term dysphagia. However, no study has tracked serial (ie, acute and late) quantitative dose-response magnetic resonance imaging (MRI) parameter kinetics in a uniform NPC dataset. We aim to characterize serial MRI signal intensity (SI) changes in dysphagia-associated volumes of interest (VOIs) as a function of the radiathin therapy dose. Materials/Methods: In this retrospective study, we extracted data on 77 patients with stage III-IV NPC who had been treated with curative intensity modulated RT (IMRT). The mean T1- and T2-weighted MRI SIs were recorded for the superior pharyngeal constrictor (SPC) and soft palate (SP) at baseline, early-after IMRT, and last follow-up, with normalization to reference structures receiving <5 Gy. RT dose grids were restored for dose response analysis. Statistical methods included a nonparametric analysis test and recursive partitioning analysis (RPA). Results: The median time to early post-RT follow-up was 4 months, and the median time to late post-RT follow-up was 41 months. The mean dose to the SPC was 62.4 Gy (standard deviation [SD], 8.7 Gy), and the mean dose to the SP was 66.8 Gy (SD, 7.3 Gy). All structures had a significant increase in T2 SIs early after treatment compared to baseline, irrespective of the mean dose given (SPC and SP, 0.470.12 and 0.560.12 at baseline vs 0.730.18 and 0.820.17, respectively, P<.0001 for both). At last follow-up, the increase in T2 SI subsided completely for SPC and partially for SP. The T1 SI did not change significantly in early follow-up images of both structures; on late follow-up, patients with mean doses >62.25 Gy had significant decrease in the corresponding T1 SI for SPC (1.6 0.4 vs 1.3 0.4, PZ.007) compared to baseline but decreased nonsignificantly for SP (1.70.5 vs 1.60.5, PZ.09). No significant changes in T1 SI were noted with doses below 62.25 Gy for both structures. Continuous RPA showed a cutoff value of magnitude 0.57 for alterations in T1 SI, with a Dmean of 63.8 Gy (95% confidence interval [CI], 61.6-66.0) for those with decrease >0.57 compared to 56.7 Gy (95% CI, 52.2-61.1) for those not achieving threshold. A sigmoidal fit was used to create a normal tissue complication probability curve for T1 alterations as a function of dose (observed R2Z0.928). Conclusion: Serial MRI acquisitions enable the identification of both early and late radiation-induced changes in swallowing structures after definitive IMRT for NPC. Decreased SI on late T1 images may indicate muscle fibrosis and is associated with higher RT doses to the SPC, while increased SI on early T2 images is associated with acute edema that subsides after therapy. Author Disclosure: J.A. Messer: None. A.S. Mohamed: None. K.A. Hutcheson: None. Y. Ding: None. J. Wang: None. H. Eichelberger: None. C. French: None. D.I. Rosenthal: None. G.B. Gunn: None. C.D. Fuller: None.
225 Prospective Comparative Study of Diffusion-Weighted MRI Versus FDG-PET for Detection of Recurrence After (Chemo)radiation for Head and Neck Squamous Cell Carcinoma J. Driessen,1 C. Terhaard,2 M. Philippens,2 and W. Grolman3; 1UMCU, Utrecht, Netherlands, 2UMC Utrecht, Utrecht, Netherlands, 3UMCU, Utrecht, Netherlands Purpose/Objective(s): High-dose (chemo)radiation for head and neck squamous cell carcinoma (HNSCC) may result in late edema and necrosis,
Posters
919
Abstract 225; Table 1 Imaging DW-MRI positive DW-MRI negative FDG-PET/CT positive FDG-PET/CT negative
Recurrence
control
24 1 35 34 1 35
8 27 35 19 16 35
32 38 70 53 17 70
resembling recurrent disease. FDG-positron emission tomography/ computed tomography (PET/CT) has a high negative predictive value for recurrent disease; however, it is limited by the positive predictive value. The diagnostic accuracy of conventional magnetic resonance imaging (MRI) with diffusion-weighted (DW) MRI to detect a local recurrence has been compared with the standard FDG-PET/CT. Materials/Methods: Seventy-four patients clinically suspected of local recurrence after (chemo)radiation for laryngeal, hypopharyngeal, or oropharyngeal cancers were prospectively included in this study and underwent an MRI including diffusion-weighted imaging (DW-MRI) and an FDG-PET/CT. Qualitative assessment of DW-MRI and FDG-PET/CT was performed by an experienced radiologist resp. nuclear physician blinded for the other modality. Reference standard was the absence of a biopsyproven local recurrence within 6 months following imaging. Results: Four patients were excluded due to contraindications or disruption of the MRI (eg, claustrophobia or patient stature). Seventy-three percent (51 of 70) of the FDG-PET/CTs were positive compared to only 46% (32 of 70) of the DW-MRI. FDG-PET/CT had a diagnostic accuracy of 72% compared to 73% for MR-DWI. The negative predictive value of FDG-PET/CT was 94% compared to 71% for MR-DWI. The positive predictive value of FDG-PET/CT was 64% compared to 75% for DW-MRI. See Table 1 for the complete results. Conclusion: In this study, DW-MRI showed superior positive predictive value but inferior negative predictive value compared to FDG-PET/CT. False negative results will cause delay in the detection of recurrence and therefore will potentially influence the chance of successful salvage surgery. Therefore, based on these results, we consider FDG-PET/CT to be superior to MR-DWI in the follow-up of HNSCC after (chemo)radiation therapy. Future improvements in DWI techniques which will decrease artefacts and enhance contrast, may enable DWI to resemble FDG-PET/CT negative predictive value without compromising the higher positive predictive value of DWI. Author Disclosure: J. Driessen: None. C. Terhaard: None. M. Philippens: None. W. Grolman: None.
226 Assessment of Laryngeal Motion Dynamics Using 4D-Computed Tomography and Dynamic Magnetic Resonance Imaging H. Bahig, P.F. Nguyen-Tan, E.J. Filion, D. Blais, D. Roberge, J. de Guise, and L. Lambert; Centre Hospitalier de l’Universite´ de Montre´al, Montreal, QC, Canada Purpose/Objective(s): With increasing interest in reduced-volume intensity modulated radiation therapy (IMRT) and intrafraction image guidance for early glottic cancer, we sought to better understand laryngeal motion. The aim of our study was to determine the dynamics of laryngeal motion during the course of a radiation treatment using combined 4dimensional computed tomography (4D-CT) and cine- magnetic resonance imaging (MRI) information. Materials/Methods: This prospective study included patients with T1-2N0 glottic cancer treated with radical radiation therapy. Dynamic sagittal MRI was obtained pretreatment and midtreatment to assess for inadvertent swallowing frequency and respiratory motion. Pre- and midtreatment 4DCT allowed for assessment of larynx excursion during swallowing and breathing as well as evaluation of gross tumor volume, clinical target volume (CTV), and planning target volume (PTV) coverage during motion. In addition, bone registration of simulation CT with pre- and
224 Longitudinal Characterization of MRI Kinetics in Irradiated Dysphagia-Related Structures for Nasopharyngeal Carcinoma Patients Receiving IMRT J.A. Messer,1 A.S.R. Mohamed,1 K.A. Hutcheson,1 Y. Ding,2 J. Wang,2 H. Eichelberger,3 C. French,3 D.I. Rosenthal,1 G.B. Gunn,2 and C.D. Fuller2; 1The University of Texas MD Anderson Cancer Center, Houston, TX, 2MD Anderson Cancer Center, Houston, TX, 3 The University of Texas Medical School, Houston, TX Purpose/Objective(s): Radiation therapy (RT) for nasopharyngeal carcinoma (NPC) is often effective at curing disease but can injure the surrounding organs at risk, including the muscles responsible for swallowing, with possible resultant short-term or long-term dysphagia. However, no study has tracked serial (ie, acute and late) quantitative dose-response magnetic resonance imaging (MRI) parameter kinetics in a uniform NPC dataset. We aim to characterize serial MRI signal intensity (SI) changes in dysphagia-associated volumes of interest (VOIs) as a function of the radiathin therapy dose. Materials/Methods: In this retrospective study, we extracted data on 77 patients with stage III-IV NPC who had been treated with curative intensity modulated RT (IMRT). The mean T1- and T2-weighted MRI SIs were recorded for the superior pharyngeal constrictor (SPC) and soft palate (SP) at baseline, early-after IMRT, and last follow-up, with normalization to reference structures receiving <5 Gy. RT dose grids were restored for dose response analysis. Statistical methods included a nonparametric analysis test and recursive partitioning analysis (RPA). Results: The median time to early post-RT follow-up was 4 months, and the median time to late post-RT follow-up was 41 months. The mean dose to the SPC was 62.4 Gy (standard deviation [SD], 8.7 Gy), and the mean dose to the SP was 66.8 Gy (SD, 7.3 Gy). All structures had a significant increase in T2 SIs early after treatment compared to baseline, irrespective of the mean dose given (SPC and SP, 0.470.12 and 0.560.12 at baseline vs 0.730.18 and 0.820.17, respectively, P<.0001 for both). At last follow-up, the increase in T2 SI subsided completely for SPC and partially for SP. The T1 SI did not change significantly in early follow-up images of both structures; on late follow-up, patients with mean doses >62.25 Gy had significant decrease in the corresponding T1 SI for SPC (1.6 0.4 vs 1.3 0.4, PZ.007) compared to baseline but decreased nonsignificantly for SP (1.70.5 vs 1.60.5, PZ.09). No significant changes in T1 SI were noted with doses below 62.25 Gy for both structures. Continuous RPA showed a cutoff value of magnitude 0.57 for alterations in T1 SI, with a Dmean of 63.8 Gy (95% confidence interval [CI], 61.6-66.0) for those with decrease >0.57 compared to 56.7 Gy (95% CI, 52.2-61.1) for those not achieving threshold. A sigmoidal fit was used to create a normal tissue complication probability curve for T1 alterations as a function of dose (observed R2Z0.928). Conclusion: Serial MRI acquisitions enable the identification of both early and late radiation-induced changes in swallowing structures after definitive IMRT for NPC. Decreased SI on late T1 images may indicate muscle fibrosis and is associated with higher RT doses to the SPC, while increased SI on early T2 images is associated with acute edema that subsides after therapy. Author Disclosure: J.A. Messer: None. A.S. Mohamed: None. K.A. Hutcheson: None. Y. Ding: None. J. Wang: None. H. Eichelberger: None. C. French: None. D.I. Rosenthal: None. G.B. Gunn: None. C.D. Fuller: None.
225 Prospective Comparative Study of Diffusion-Weighted MRI Versus FDG-PET for Detection of Recurrence After (Chemo)radiation for Head and Neck Squamous Cell Carcinoma J. Driessen,1 C. Terhaard,2 M. Philippens,2 and W. Grolman3; 1UMCU, Utrecht, Netherlands, 2UMC Utrecht, Utrecht, Netherlands, 3UMCU, Utrecht, Netherlands Purpose/Objective(s): High-dose (chemo)radiation for head and neck squamous cell carcinoma (HNSCC) may result in late edema and necrosis,
Posters
919
Abstract 225; Table 1 Imaging DW-MRI positive DW-MRI negative FDG-PET/CT positive FDG-PET/CT negative
Recurrence
control
24 1 35 34 1 35
8 27 35 19 16 35
32 38 70 53 17 70
resembling recurrent disease. FDG-positron emission tomography/ computed tomography (PET/CT) has a high negative predictive value for recurrent disease; however, it is limited by the positive predictive value. The diagnostic accuracy of conventional magnetic resonance imaging (MRI) with diffusion-weighted (DW) MRI to detect a local recurrence has been compared with the standard FDG-PET/CT. Materials/Methods: Seventy-four patients clinically suspected of local recurrence after (chemo)radiation for laryngeal, hypopharyngeal, or oropharyngeal cancers were prospectively included in this study and underwent an MRI including diffusion-weighted imaging (DW-MRI) and an FDG-PET/CT. Qualitative assessment of DW-MRI and FDG-PET/CT was performed by an experienced radiologist resp. nuclear physician blinded for the other modality. Reference standard was the absence of a biopsyproven local recurrence within 6 months following imaging. Results: Four patients were excluded due to contraindications or disruption of the MRI (eg, claustrophobia or patient stature). Seventy-three percent (51 of 70) of the FDG-PET/CTs were positive compared to only 46% (32 of 70) of the DW-MRI. FDG-PET/CT had a diagnostic accuracy of 72% compared to 73% for MR-DWI. The negative predictive value of FDG-PET/CT was 94% compared to 71% for MR-DWI. The positive predictive value of FDG-PET/CT was 64% compared to 75% for DW-MRI. See Table 1 for the complete results. Conclusion: In this study, DW-MRI showed superior positive predictive value but inferior negative predictive value compared to FDG-PET/CT. False negative results will cause delay in the detection of recurrence and therefore will potentially influence the chance of successful salvage surgery. Therefore, based on these results, we consider FDG-PET/CT to be superior to MR-DWI in the follow-up of HNSCC after (chemo)radiation therapy. Future improvements in DWI techniques which will decrease artefacts and enhance contrast, may enable DWI to resemble FDG-PET/CT negative predictive value without compromising the higher positive predictive value of DWI. Author Disclosure: J. Driessen: None. C. Terhaard: None. M. Philippens: None. W. Grolman: None.
226 Assessment of Laryngeal Motion Dynamics Using 4D-Computed Tomography and Dynamic Magnetic Resonance Imaging H. Bahig, P.F. Nguyen-Tan, E.J. Filion, D. Blais, D. Roberge, J. de Guise, and L. Lambert; Centre Hospitalier de l’Universite´ de Montre´al, Montreal, QC, Canada Purpose/Objective(s): With increasing interest in reduced-volume intensity modulated radiation therapy (IMRT) and intrafraction image guidance for early glottic cancer, we sought to better understand laryngeal motion. The aim of our study was to determine the dynamics of laryngeal motion during the course of a radiation treatment using combined 4dimensional computed tomography (4D-CT) and cine- magnetic resonance imaging (MRI) information. Materials/Methods: This prospective study included patients with T1-2N0 glottic cancer treated with radical radiation therapy. Dynamic sagittal MRI was obtained pretreatment and midtreatment to assess for inadvertent swallowing frequency and respiratory motion. Pre- and midtreatment 4DCT allowed for assessment of larynx excursion during swallowing and breathing as well as evaluation of gross tumor volume, clinical target volume (CTV), and planning target volume (PTV) coverage during motion. In addition, bone registration of simulation CT with pre- and