Dosimetric impact of positron emission tomography-based gross tumour volume (GTV) delineation over conventional CT-based GTV delineation for carcinoma oesophagus

Aim: The aim of the study was to find the dosimetric impact of positron emission tomography (PET)-based gross tumour volume (GTV) delineation over computed tomography (CT)-based GTV delineation for carcinoma oesophagus. Methods: Fifteen patients with carcinoma oesophagus were retrospectively selected. Two sets of GTVs in CT plain images were generated, one with the help of intravenous and oral contrast (GTV CT) and the other with only using PET uptake with the standardised uptake value (simple way of determining the activity in PET) (SUV) > 2.5 (GTV PET). Corresponding PTVs were generated. For all patients, rapid arc plans were generated. Changes in target volumes and critical structure doses were evaluated. The Wilcoxon signed-rank test was used for statistical analysis, and p value < 0.05 was assumed as statistically significant. Results: Mean reduction in GTV was 5.76 +/- 19.35 cc. Mean reduction in PTV 45 Gy was 42.40 +/- 76.39 cc. Mean reduction in heart mean dose was 1.53 +/- 2.16 Gy. Mean reductions in left lung V20% and V10% were 2.43 +/- 4.28 and 3.25 +/- 5.09 Gy, respectively. Mean reductions in right lung V20% and V10% were 3.11 +/- 4.91 and 2.80 +/- 4.51 Gy, respectively. Mean reduction in total lung mean dose was 1.00 +/- 1.19 Gy. Finding: PET-based GTV contouring reduces the treatment volume and critical structure doses significantly over CT-based GTV contouring for carcinoma oesophagus.