18-Fluorodeoxy-Glucose Positron Emission Tomography- Computed Tomography (18-FDG-PET/CT) for Gross Tumor Volume (GTV) Delineation in Gastric Cancer Radiotherapy

Dębiec, Kinga; Wydmański, Jerzy; Gorczewska, Izabela; Leszczyńska, Paulina; Gorczewski, Kamil; Leszczynski, Wojciech; D’Amico, Andrea; Kalemba, Michał

doi:10.22034/APJCP.2017.18.11.2989

18-Fluorodeoxy-Glucose Positron Emission Tomography- Computed Tomography (18-FDG-PET/CT) for Gross Tumor Volume (GTV) Delineation in Gastric Cancer Radiotherapy

Document Type : Research Articles

Authors

¹ Radiotherapy and Chemotherapy I Clinic, Maria Skłodowska-Curie Memorial Institute of Oncology, Gliwice Branch, Poland.

² Department of Radiotherapy, Maria Skłodowska-Curie Memorial Institute of Oncology, Gliwice Branch, Poland.

³ Department of PET Diagnostics, Maria Skłodowska-Curie Memorial Institute of Oncology, Gliwice Branch, Poland.

⁴ Department of Radiotherapy Planning, Maria Skłodowska-Curie Memorial Institute of Oncology, Gliwice Branch, Poland.

⁵ Department of Nuclear Medicine and Endocrine Oncology, Maria Skłodowska-Curie Memorial Institute of Oncology, Gliwice Branch, Poland.

10.22034/APJCP.2017.18.11.2989

Abstract

Purpose: Evaluation of the 18-fluorodeoxy-glucose positron emission tomography-computed tomography (18-FDG-PET/_CT) for gross tumor volume (GTV) delineation in gastric cancer patients undergoing radiotherapy. Methods: In this study, 29 gastric cancer patients (17 unresectable and 7 inoperable) were initially enrolled for radical chemoradiotherapy (45Gy/25 fractions + chemotherapy based on 5 fluorouracil) or radiotherapy alone (45Gy/25 fractions) with planning based on the 18-FDG-PET/CT images. Five patients were excluded due to excess blood glucose levels (1), false-negative positron emission tomography (1) and distant metastases revealed by 18-FDG-PET/_CT (3). The analysis involved measurement of metabolic tumor volumes (MTVs) performed on PET/CT workstations. Different threshold levels of the standardized uptake value (SUV) and liver uptake were set to obtain MTVs. Secondly, GTVPET values were derived manually using the positron emission tomography (PET) dataset blinded to the computed tomography (CT) data. Subsequently, GTV_CTvalues were delineated using a radiotherapy planning system based on the CT scans blinded to the PET data. The referenced GTV_CTvalues were correlated with the GTV_PETand were compared with a conformality index (CI). Results: The mean CI was 0.52 (range, 0.12-0.85). In 13/24 patients (54%), the GTVPET was larger than GTV_CT, and in the remainder, GTVPET was smaller. Moreover, the cranio-caudal diameter of GTVPET in 16 cases (64%) was larger than that of GTV_CT, smaller in 7 cases (29%), and unchanged in one case. Manual PET delineation (GTV_PET) achieved the best correlation with GTV_CT(Pearson correlation = 0.76, p <0.0001). Among the analyzed MTVs, a statistically significant correlation with GTV_CT was revealed for MTV_10%SUVmax(r = 0.63; p = 0.0014), MTV_liv(r = 0.60; p = 0.0021), MTVSUV2.5 (r = 0.54; p = 0.0063); MTV20%SUVmax (r = 0.44; p = 0.0344); MTV_30%SUVmax(r = 0.44; p = 0.0373). Conclusion: 18-FDG-PET/_CTin gastric cancer radiotherapy planning may affect the GTV delineation.

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