PET-based dose painting in non-small cell lung cancer: Comparing uniform dose escalation with boosting hypoxic and metabolically active sub-volumes

Background and purpose: We compared two imaging biomarkers for dose-escalation in patients with advanced non-small cell lung cancer (NSCLC). Treatment plans boosting metabolically active sub-volumes defined by FOG-PET or hypoxic sub-volumes defined by HX4-PET were compared with boosting the entire tumour. Materials and methods: Ten NSCLC patients underwent FDG- and HX4-PET/CT scans prior to radiotherapy. Three isotoxic dose-escalation plans were compared per patient: plan A, boosting the primary tumour (PTVprim); plan B, boosting sub-volume with FDG >50% SUVmax (PTVFDG); plan C, boosting hypoxic volume with HX4 tumour-to-background >1.4 (PTVHX4). Results: Average boost volumes were 507 +/- 466 cm(3) for PTVprim, 173 +/- 127 cm(3) for PTVFDG and 114 +/- 73 cm(3) for PTVHX4. The smaller PTVHX4 overlapped on average 87 +/- 16% with PTVFDG. Prescribed dose was escalated to 87 +/- 10 Gy for PTVprim, 107 +/- 20 Gy for PTVFDG, and 117 +/- 15 Gy for PTVHX4, with comparable doses to the relevant organs-at-risk (OAR). Treatment plans are available online (https://www.cancerdata.org/10.1016/j.radonc.2015.07.013). Conclusions: Dose escalation based on metabolic sub-volumes, hypoxic sub-volumes and the entire tumour is feasible. Highest dose was achieved for hypoxia plans, without increasing dose to OAR. For most patients, boosting the metabolic sub-volume also resulted in boosting the hypoxic volume, although to a lower dose, but not vice versa.