Investigating the Impact of Positron Emission Tomography-Computed Tomography Versus Computed Tomography Alone for High-risk Volume Selection in Head and Neck and Lung Patients Undergoing Radiotherapy: Interim Findings

Introduction: The aim of this study was to quantify the impact of positron emission tomography-computed tomography (PET-CT) on clinical target volume (CTV) selection in non-small cell lung cancer (NSCLC) and head and neck squamous cell cancer (HNSCC) cancer patients.

Methods: Eight radiation oncologists with expertise in either NSCLC or HNSCC prospectively contoured target volumes with and without PET-CT findings. All volumes were contoured manually, and computed tomography (CT)-alone contours were identified as gross tumour volume CT and clinical target volume (CTV) CT, whereas those contoured with the aid of PET-CT were GTV PET and CTV PET. PET-CT contours were used for actual treatment delivery. Test treatment plans were generated based on the CT-alone volumes and applied to the final PET-CT contours. PET-CT had an impact if the test plans failed department quality assurance guidelines. For each patient, the dose to critical structures and any changes in the treatment plan were recorded.

Results: Eighty patients (49 HNSCC and 31 NSCLC) were analyzed. PET-CT impacted 42.9% of HNSCC cases and 45.2% of NSCLC cases. On average, PET-CT volumes were significantly larger than CT-alone volumes for HNSCC cases (P < .01) but not for NSCLC cases (P = .29). For organs at risk, no statistically significant differences were noted, with the exception of mean parotid dose for the right and left parotids (P = .0137and P = .0330, respectively).

Conclusions: Interim analysis of data found that the use of PET-CT in the radiation therapy planning process impacted CTV selection, resulting in a major change in radiation therapy plans in 43.7% (HNSCC 42.9% and NSCLC 45.2%) of patients.