Resumen de Radiotherapy volume delineation using 18F-FDG-PET/CT modifies gross node volume in patients with oesophageal cancer

Esther Jimenez Jimenez, Pedro Mateos Salvador, Neus Aymar, Raquel Roncero, Irene Ortiz González, Marta Giménez García, José Pardo Masferrer, Juan Salinas Ramos, Sebastià Sabater

• Purpose Evidence supporting the use of 18F-FDG-PET/CT in the segmentation process of oesophageal cancer for radiotherapy planning is limited. Our aim was to compare the volumes and tumour lengths defined by fused PET/CT vs. CT simulation.

  Materials and methods Twenty-nine patients were analyzed. All patients underwent a single PET/CT simulation scan. Two separate GTVs were defined: one based on CT data alone and another based on fused PET/CT data. Volume sizes for both data sets were compared and the spatial overlap was assessed by the Dice similarity coefficient (DSC).

  Results The gross tumour volume (GTVtumour) and maximum tumour diameter were greater by PET/CT, and length of primary tumour was greater by CT, but differences were not statistically significant. However, the gross node volume (GTVnode) was significantly greater by PET/CT. The DSC analysis showed excellent agreement for GTVtumour, 0.72, but was very low for GTVnode, 0.25.

  Conclusions Our study shows that the volume definition by PET/CT and CT data differs. CT simulation, without taking into account PET/CT information, might leave cancer-involved nodes out of the radiotherapy-delineated volumes.