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.