Respiratory-gated (4D) contrast-enhanced FDG PET-CT for radiotherapy planning of lower oesophageal carcinoma: feasibility and impact on planning target volume.

BACKGROUND

To assess the feasibility and potential impact on target delineation of respiratory-gated (4D) contrast-enhanced Fluorine fluorodeoxyglucose (FDG) positron emission tomography - computed tomography (PET-CT), in the treatment planning position, for a prospective cohort of patients with lower third oesophageal cancer.

METHODS

Fifteen patients were recruited into the study. Imaging included 4D PET-CT, 3D PET-CT, endoscopic ultrasound and planning 4D CT. Target volume delineation was performed on 4D CT, 4D CT with co-registered 3D PET and 4D PET-CT. Planning target volumes (PTV) generated with 4D CT (PTV 4D CT co-registered with 3D PET-CT (PTV and 4D PET-CT (PTV) were compared with multiple positional metrics.

RESULTS

Mean PTV, PTV and PTV were 582.4 ± 275.1 cm, 472.5 ± 193.1 cm and 480.6 ± 236.9 cm respectively (no significant difference). Median DICE similarity coefficients comparing PTV with PTV PTV with PTV and PTV with PTV were 0.85 (range 0.65-0.9), 0.85 (range 0.69-0.9) and 0.88 (range 0.79-0.9) respectively. The median sensitivity index for overlap comparing PTV with PTV PTV with PTV and PTV with PTV were 0.78 (range 0.65-0.9), 0.79 (range 0.65-0.9) and 0.89 (range 0.68-0.94) respectively.

CONCLUSIONS

Planning 4D PET-CT is feasible with careful patient selection. PTV generated using 4D CT, 3D PET-CT and 4D PET-CT were of similar volume, however, overlap analysis demonstrated that approximately 20% of PTV and PTV are not included in PTV, leading to under-coverage of target volume and a potential geometric miss. Additionally, differences between PTV and PTV suggest a potential benefit for 4D PET-CT.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier - NCT02285660 (Registered 21/10/2014).