The value of positron-emission tomography/computed tomography for radiotherapy treatment planning

Abstract

This study aimed to compare the clinical target volumes (CTV) delineated by computed tomography (CT) and positron emission tomography (PET)/CT using fluoro-deoxy-glucose to assess the impact of using PET information for radiotherapy (RT) planning. We retrospectively reviewed data on patients with tumors from different sites who had indications for RT and had undergone RT treatment planning with PET/CT at our institution between July 2003 and July 2009. Statistical analysis included the comparison of CTV planned for treatment only by CT (CTV(CT)) with that by PET/CT (CTV(PET)) using the Wilcoxon test for paired samples. Of 105 patients eligible for analysis, 56.2% were men. The most common diagnoses were head and neck cancer (28.6%), lung cancer (21.9%), lymphoma (11.4%), upper gastrointestinal (10.5%), and others (14.3%). Comparison of CTV(CT) and CTV(PET) revealed that RT planning has changed in 77% of cases because of PET/CT additional information, with impact on treatment volume varying according to diagnosis. Despite the absolute difference observed between median CTVs, there was no significant difference between CTV(CT) and CTV(PET) (114 vs. 90.4 ml, respectively; P=0.1266), considering all patients. Nonetheless, a significant difference between CTVs delineated by CT and PET/CT was found when only head and neck, lung and lymphoma cases--representing more than 60% of the sample--were examined (112.5 and 80.7 ml, respectively; P=0.0053). We have shown that PET/CT use promotes significant changes in the CTV delineated for treatment of different tumors, modifying RT planning. Our data suggest that PET/CT has a good potential for optimizing RT treatment planning, especially in head and neck, lung, and lymphoma tumors.