18F-Fludeoxyglucose PET/CT in SCLC: Analysis of the CONVERT Randomized Controlled Trial

Introduction We used phase-3 CONVERT trial data to investigate the impact of fludeoxyglucose F 18 ( 18 F-FDG) positron emission tomography (PET)/computed tomography (CT) in SCLC. Methods CONVERT randomized patients with limited-stage SCLC to twice-daily (45 Gy in 30 fractions) or once-daily (66 Gy in 33 fractions) chemoradiotherapy. Patients were divided into two groups in this unplanned analysis: those staged with conventional imaging (contrast-enhanced thorax and abdomen CT and brain imaging with or without bone scintigraphy) and those staged with 18 F-FDG PET/CT in addition. Results Data on a total of 540 patients were analyzed. Compared with patients who underwent conventional imaging (n = 231), patients also staged with 18 F-FDG PET/CT (n = 309) had a smaller gross tumor volume ( p = 0.003), were less likely to have an increased pretreatment serum lactate dehydrogenase level ( p = 0.035), and received more chemotherapy ( p = 0.026). There were no significant differences in overall (hazard ratio = 0.87, 95% confidence interval: 0.70–1.08, p = 0.192) and progression-free survival (hazard ratio = 0.87, 95% confidence interval: 0.71–1.07], p = 0.198) between patients staged with or without 18 F-FDG PET/CT. In the conventional imaging group, we found no survival difference between patients staged with or without bone scintigraphy. Although there were no differences in delivered radiotherapy dose, 18 F-FDG PET/CT–staged patients received lower normal tissue (lung, heart, and esophagus) radiation doses. Apart from a higher incidence of late esophagitis in patients staged with conventional imaging (for grade ≥1, 19% versus 11%; [ p = 0.012]), the incidence of acute and late radiotherapy-related toxicities was not different between the two groups. Conclusion In CONVERT, survival outcomes were not significantly different in patients staged with or without 18 F-FDG PET/CT. However, this analysis cannot support the use or omission of 18 F-FDG PET/CT owing to study limitations.