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CT in radiation treatment planning for patients with esophageal cancer
S16 described (Magn Reson Med 2013, 70, 732-744). This non-invasive method is based on the changes in the relaxation properties of the tissue lipids by exploiting the higher solubility property of oxygen in lipids than in water. The purpose of the present study was first to assess the value of this method in pre-clinical models exposed to hyperoxic challenges (carbogen breathing) or hypoxic challenges using a vascular disrupting agent known to induce hypoxia. Actual pO2 was obtained by EPR oximetry and compared to Lipid R1. In a second step, we implement the MOBILE sequence on a clinical MRI scanner and evaluate Lipid R1 in glioma patients. Materials and Methods: Mammary NT2 and human MDA-MB-231 tumor models were used. Experiments were performed with a 11.7T using a surface coil cryoprobe. A segmented IR FISP sequence was used to acquire parametric images of T1 relaxation time centered on the lipid peak after suppression of the water signal. Hyperoxic challenge: Images were acquired at baseline and 10 minutes after a switch to carbogen breathing. The same challenge was repeated 3hours later to achieve actual pO2 by EPR oximetry.Hypoxic challenge: Images were acquired at baseline and 3hours after CA4P injection (100mg/kg). Clinical studies were obtained on a 3T MRI scanner. MOBILE images were obtained on 25 patients with neuroepithelial tumors. Results
ESTRO 33, 2014 1
University Medical Center Groningen University of Groningen, Radiation Oncology, Groningen, The Netherlands Medisch Spectrum Twente, Radiation Oncology, Groningen, The Netherlands 3 University Medical Center Gronigen University of Groningen, Radiology, Groningen, The Netherlands 4 University Medical Center Gronigen University of Groningen, Molecular imaging and Nuclear Medicine, Groningen, The Netherlands 5 University Medical Center Gronigen University of Groningen, Medical Oncology, Groningen, The Netherlands 6 University Medical Center Gronigen University of Groningen, Epidemiology, Groningen, The Netherlands 7 University Medical Center Gronigen University of Groningen, Surgical Oncology, Groningen, The Netherlands 2
Purpose/Objective: The aim of this prospective study was to determine the additional value of PET/CT for radiotherapy treatment planning in esophageal cancer by assessing the proportion of patients in which locoregional recurrences (LRR) could have been prevented if PET/CTbased treatment planning was used instead of CT-based treatment planning. Materials and Methods: Ninety esophageal cancer patients who were planned for high dose (chemo)radiotherapy, as primary treatment or in neo-adjuvant setting followed by surgical resection, were included in this prospective cohort trial (RESPECT). All patients underwent a planning FDG-PET/CT-scan. Radiotherapy target volumes were delineated on planning CT only and patients were treated according to the CT-based treatment plans. The PET images remained blinded. After treatment, the PET/CT was used to adjust the target volumes when appropriate. Follow up included routine CT-thorax/abdomen every half year. If LRR was suspected, an additional PET/CT was conducted in the original treatment position and the site of recurrence was compared to the original target volumes. If the recurrence was located outside or at the border of the CT-based clinical target volume (CTV) and inside the PET/CT-based CTV, we considered this as an event and as a possibly preventable. Results: Based on the additional PET information, the gross tumour volume (GTV) was enlarged in 23% and reduced in 27% of the cases. The proportion of the PET/CT-based GTV that would be missed if the treatment planning was based on CT, was >5% in 32 patients (36%). The median follow up time was 29 months (95% CI 24.0-34.0). LRR were seen in 10 patients (11%), with synchronic distant metastases in 3 patients. All LRR were considered not preventable by the use of PET/CT, since 3 were located within the radiation-field, while in 4 the recurrences were located regionally, but outside both the CT- and PET/CT-based CTV. Three patients showed a recurrence at the anastomosis, however in these patients there were no changes in target volumes. Distant metastases were the most frequently reported first site of recurrence (36%). Conclusions: In this prospective study, no preventable LRRs were found by the addition of FDG-PET/CT. Therefore, the additional value of PET/CT for the radiotherapy treatment planning for esophageal cancer remains limited in terms of prevention of LRRs.
In tumor models, a significant linear regression was demonstrated between actual pO2 and mean Lipids R1 calculated for each tumor (Fig.1A). So far, 28 primary central nervous system tumoral areas were analyzed in the clinical studies. Regions of interest (ROIs) contouring contrast-enhancing tumour (C+, presumptively of histological high grade), tumour not uptaking contrast (C-, presumptively of low grade), tumoral oedema and Normal Appearing White Matter (NAWM) (Fig.2B). Pooled mean Lipids R1 values (C+ and C-) were significantly higher than Lipids R1 obtained for oedema and NAWM . However, no statistical difference between C+ and C- tumors could be shown. Conclusions: Actual pO2 significantly correlated to mean values of Lipids R1 obtained with MOBILE at baseline and after both hyperoxic and hypoxic challenges, induced respectively by carbogen breathing and CA4P administration. The implementation of the technique in the clinic has been achieved on glioma patients. The MOBILE sequence enables the distinction between tumoral areas and normal areas. These data support the potential interest for MOBILE as an non invasive marker of tumor oxygenation. OC-0045 Clinical validation on the role of FDG-PET/CT in radiation treatment planning for patients with esophageal cancer C.T. Muijs1, J.C. Beukema1, D. Woutersen2, V.E.M. Mul1, E.J. Van der Jagt3, J. Pruim4, G. Hospers5, H. Groen6, J.T.H. Plukker7, J.A. Langendijk1
OC-0046 Analysis of the spatial dosimetric sensitivity of contouring uncertainties in gynecological brachytherapy M. Arnesen1, T.P. Hellebust1, E. Malinen2 1 Oslo University Hospital Norwegian Radium Hospital, Department of Medical Physics, Oslo, Norway 2 University of Oslo, Department of Physics, Oslo, Norway Purpose/Objective: Steep dose gradients exist in highly conformal radiotherapy. Uncertainties in target contouring will therefore have significant impact on DVH parameters and may undermine overall efficacy of such treatments. This study aims to systematically analyse the spatial dosimetric sensitivity of such uncertainties in 3D-based gynaecological brachytherapy. Materials and Methods: A methodology to estimate the spatial dosimetric sensitivity of contouring uncertainties was developed. Errors in delineated contours were simulated by shifting an angular segment of the contour perpendicular to the original contour, where the maximum shift was 3, 6, or 9 mm. For each shift, the resulting D90 and D98 for HRCTV were calculated based on the modified contour. The sensitivity of the dose plan to the introduced error (in [% of prescribed dose/mm]) was estimated by a linear regression of D90 or D98 against the magnitude of the shift. To visualize the spatial dependence of the sensitivity, 2D colour maps was created with image slice position in one direction and angle of a given contour point relative to the centroid in the other. The
ESTRO 33, 2014 1
University Medical Center Groningen University of Groningen, Radiation Oncology, Groningen, The Netherlands Medisch Spectrum Twente, Radiation Oncology, Groningen, The Netherlands 3 University Medical Center Gronigen University of Groningen, Radiology, Groningen, The Netherlands 4 University Medical Center Gronigen University of Groningen, Molecular imaging and Nuclear Medicine, Groningen, The Netherlands 5 University Medical Center Gronigen University of Groningen, Medical Oncology, Groningen, The Netherlands 6 University Medical Center Gronigen University of Groningen, Epidemiology, Groningen, The Netherlands 7 University Medical Center Gronigen University of Groningen, Surgical Oncology, Groningen, The Netherlands 2
Purpose/Objective: The aim of this prospective study was to determine the additional value of PET/CT for radiotherapy treatment planning in esophageal cancer by assessing the proportion of patients in which locoregional recurrences (LRR) could have been prevented if PET/CTbased treatment planning was used instead of CT-based treatment planning. Materials and Methods: Ninety esophageal cancer patients who were planned for high dose (chemo)radiotherapy, as primary treatment or in neo-adjuvant setting followed by surgical resection, were included in this prospective cohort trial (RESPECT). All patients underwent a planning FDG-PET/CT-scan. Radiotherapy target volumes were delineated on planning CT only and patients were treated according to the CT-based treatment plans. The PET images remained blinded. After treatment, the PET/CT was used to adjust the target volumes when appropriate. Follow up included routine CT-thorax/abdomen every half year. If LRR was suspected, an additional PET/CT was conducted in the original treatment position and the site of recurrence was compared to the original target volumes. If the recurrence was located outside or at the border of the CT-based clinical target volume (CTV) and inside the PET/CT-based CTV, we considered this as an event and as a possibly preventable. Results: Based on the additional PET information, the gross tumour volume (GTV) was enlarged in 23% and reduced in 27% of the cases. The proportion of the PET/CT-based GTV that would be missed if the treatment planning was based on CT, was >5% in 32 patients (36%). The median follow up time was 29 months (95% CI 24.0-34.0). LRR were seen in 10 patients (11%), with synchronic distant metastases in 3 patients. All LRR were considered not preventable by the use of PET/CT, since 3 were located within the radiation-field, while in 4 the recurrences were located regionally, but outside both the CT- and PET/CT-based CTV. Three patients showed a recurrence at the anastomosis, however in these patients there were no changes in target volumes. Distant metastases were the most frequently reported first site of recurrence (36%). Conclusions: In this prospective study, no preventable LRRs were found by the addition of FDG-PET/CT. Therefore, the additional value of PET/CT for the radiotherapy treatment planning for esophageal cancer remains limited in terms of prevention of LRRs.
In tumor models, a significant linear regression was demonstrated between actual pO2 and mean Lipids R1 calculated for each tumor (Fig.1A). So far, 28 primary central nervous system tumoral areas were analyzed in the clinical studies. Regions of interest (ROIs) contouring contrast-enhancing tumour (C+, presumptively of histological high grade), tumour not uptaking contrast (C-, presumptively of low grade), tumoral oedema and Normal Appearing White Matter (NAWM) (Fig.2B). Pooled mean Lipids R1 values (C+ and C-) were significantly higher than Lipids R1 obtained for oedema and NAWM . However, no statistical difference between C+ and C- tumors could be shown. Conclusions: Actual pO2 significantly correlated to mean values of Lipids R1 obtained with MOBILE at baseline and after both hyperoxic and hypoxic challenges, induced respectively by carbogen breathing and CA4P administration. The implementation of the technique in the clinic has been achieved on glioma patients. The MOBILE sequence enables the distinction between tumoral areas and normal areas. These data support the potential interest for MOBILE as an non invasive marker of tumor oxygenation. OC-0045 Clinical validation on the role of FDG-PET/CT in radiation treatment planning for patients with esophageal cancer C.T. Muijs1, J.C. Beukema1, D. Woutersen2, V.E.M. Mul1, E.J. Van der Jagt3, J. Pruim4, G. Hospers5, H. Groen6, J.T.H. Plukker7, J.A. Langendijk1
OC-0046 Analysis of the spatial dosimetric sensitivity of contouring uncertainties in gynecological brachytherapy M. Arnesen1, T.P. Hellebust1, E. Malinen2 1 Oslo University Hospital Norwegian Radium Hospital, Department of Medical Physics, Oslo, Norway 2 University of Oslo, Department of Physics, Oslo, Norway Purpose/Objective: Steep dose gradients exist in highly conformal radiotherapy. Uncertainties in target contouring will therefore have significant impact on DVH parameters and may undermine overall efficacy of such treatments. This study aims to systematically analyse the spatial dosimetric sensitivity of such uncertainties in 3D-based gynaecological brachytherapy. Materials and Methods: A methodology to estimate the spatial dosimetric sensitivity of contouring uncertainties was developed. Errors in delineated contours were simulated by shifting an angular segment of the contour perpendicular to the original contour, where the maximum shift was 3, 6, or 9 mm. For each shift, the resulting D90 and D98 for HRCTV were calculated based on the modified contour. The sensitivity of the dose plan to the introduced error (in [% of prescribed dose/mm]) was estimated by a linear regression of D90 or D98 against the magnitude of the shift. To visualize the spatial dependence of the sensitivity, 2D colour maps was created with image slice position in one direction and angle of a given contour point relative to the centroid in the other. The