INTRODUCTION: We used phase-3 CONVERT trial data to investigate the impact of 18fludeoxyglucose (18F-FDG) PET/CT in small-cell lung cancer (SCLC).
METHODS: CONVERT randomized limited-stage SCLC patients to twice-daily (45Gy in 30-fractions) or once-daily (66Gy in 33-fractions) chemoradiotherapy. Patients were divided into 2 groups in this unplanned analysis: those staged with conventional imaging (contrast-enhanced thorax and abdomen CT and brain imaging with/without bone scintigraphy) and those staged with 18F-FDG PET/CT in addition.
RESULTS: 540 patients were analyzed. Compared to patients who underwent conventional imaging (n=231), patients also staged with 18F-FDG PET/CT (n=309) had smaller gross tumor volume (P=0·003), were less likely to have elevated pre-treatment serum lactate dehydrogenase (P=0·035), and received more chemotherapy (P=0·026). There were no significant differences in overall (HR 0·87 [95% CI 0·70-1·08]; P=0·192) and progression-free survival (HR 0·87 [95% CI 0·71-1·07]; P=0·198) between patients staged with or without 18F-FDG PET/CT. In the conventional imaging group, we found no survival difference between patients staged with or without bone scintigraphy. While there were no differences in delivered radiotherapy dose, 18F-FDG PET/CT-staged patients received lower normal tissue (lung, heart, and esophagus) radiation doses. Apart from higher incidence of late esophagitis in patients staged with conventional imaging (grade ≥1: 19% vs 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 18F-FDG PET/CT. However, this analysis cannot support the use or omission of 18F-FDG PET/CT due to study limitations.