Gastrointestinal Cancer

PV 04 - Poster Viewing Q&A - Session 4

TU_10_2460 - Motion-Compensated FDG PET/CT for Esophageal Cancer

Tuesday, September 17
2:45 PM - 4:00 PM
Location: ASTRO Innovation Hub

Motion-Compensated FDG PET/CT for Esophageal Cancer
F. E. M. Voncken1, E. Vegt2, J. W. Sandick3, J. M. van Dieren4, C. Grootscholten4, A. Bartels-Rutten5, S. L. Takken1, J. J. Sonke1, J. B. van de Kamer1, and B. M. P. Aleman1; 1The Netherlands Cancer Institute (NKI-AVL), Department of Radiation Oncology, Amsterdam, Netherlands, 2The Netherlands Cancer Institute (NKI-AVL), Department of Nuclear Medicine, Amsterdam, Netherlands, 3The Netherlands Cancer Institute (NKI-AVL), Department of Surgical Oncology, Amsterdam, Netherlands, 4The Netherlands Cancer Institute (NKI-AVL), Department of Gastrointestinal Oncology, Amsterdam, Netherlands, 5The Netherlands Cancer Institute (NKI-AVL), Department of Radiology, Amsterdam, Netherlands

Purpose/Objective(s): Motion of esophageal tumors and loco-regional lymph nodes may reduce the sensitivity of positron emission tomography with computed tomography (PET/CT) for the detection of esophageal tumors and lymph node metastases. The aims of this study were to assess the value of motion-compensated (four-dimensional, 4D) PET/CT for detection of esophageal lymph node metastases, and to quantify the impact of 4D PET/CT on maximum standardized uptake value (SUVmax) and metabolic tumor volume (MTV) for (semi) automated threshold-based tumor delineation in esophageal cancer patients.

Materials/Methods: This prospective observational study included newly diagnosed esophageal cancer patients who were scheduled for whole body 18F-fluorodeoxyglucose (FDG) PET/CT as part of diagnostic work-up. PET and CT of the thorax and upper abdomen were acquired in 4D mode. Motion amplitude was measured at the primary tumor location. From the 10 breathing phases a time-averaged mid position scan was reconstructed (4D), in addition to the three-dimensional (3D) reconstruction. A nuclear medicine physician assessed all scans blinded for reconstruction mode. Scan quality was rated on a five-point scale (very good, good, acceptable, poor and very poor). All lymph nodes showing FDG uptake were assessed for their degree of suspicion for metastasis on a four-point scale (highly suspicious, suspicious, dubious or unlikely). The primary tumor was semi-automatically contoured using an automated growing region algorithm with SUV thresholds of 2.5 and 50% of the maximum SUV. MTVs using these thresholds were calculated. Comparisons were made between 3D and 4D results.

Results: Thirty-seven patients were included, of whom 27 (73%) were node positive on PET/CT. Tumors were mainly located in the distal esophagus (30%) or at the gastro-esophageal junction (41%). Median craniocaudal breathing amplitude was 6.0 mm (range 0-21 mm). Scans were rated as good quality in 65% (3D) and 68% (4D). The number of lymph nodes classified as highly suspicious, suspicious and dubious for metastases on 3D vs. 4D PET/CT, was 30 vs. 34, 20 vs. 22, and 66 vs. 59 respectively. No additional lymph node metastases were found on 4D PET compared to 3D PET. SUVmax of the primary tumor was similar on 3D and 4D PET/CT: mean (SD) 13.1 (7.3) versus 13.0 (7.9) respectively (p=0.81). SUVmax of suspicious lymph nodes was also similar between both scans: mean (SD) 6.6 (6.2) on 3D versus 6.8 (6.3) on 4D PET/CT (p=0.18). Furthermore, MTVs were similar between 3D and 4D scans. For tumors with a relatively low SUVmax (≤8.0), however, differences in MTV SUVmax≥50% varied between -81% and +160% on the 3D and 4D scan.

Conclusion: Motion-compensated FDG PET/CT did not improve lymph node detection. SUVmax of the primary tumor and lymph nodes were comparable on 3D and 4D PET/CT. The impact of the 4D technique on semi-automated segmentation of the primary tumor was subtle on average, but large differences were seen in tumors with a SUVmax of ≤8.0 for MTV SUVmax≥50%.

Author Disclosure: F.E. Voncken: None. E. Vegt: None. J.M. van Dieren: None. C. Grootscholten: None. A. Bartels-Rutten: None. J. Sonke: Research Grant; Elekta Oncology Systems Ltd. associate editor; Medical Physics. license fees; Elekta Oncology Systems AB. B.M. Aleman: Project leader; The Dutch Cancer Society.

Berthe Aleman, MD, PhD

Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital (NKI-AVL)

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