UNLABELLED: There is an increasing amount of evidence on the usability of PET in response evaluation of non-small cell lung cancer. However, data on SCLC is scarce and mainly retrospective. This prospective study assesses the use of PET (positron emission tomography) and PET/CT in response evaluation of patients with small cell lung cancer (SCLC).

METHODS: Assignment of early and final response was compared between PET, PET/CT, and CT in 20 patients with SCLC. Final response as assigned by CT (RECIST) served as reference.

RESULTS: At response evaluation after one cycle of chemotherapy major disagreement (responder versus non-responder) between PET and CT in predicting final response was seen in 1 of 12 patients. At final response evaluation major disagreement between PET, PET/CT and CT was seen in 2 of 19 patients (11%). All measurements of FDG-uptake were significantly correlated to size and changes in size as measured by CT. A significant difference in relative change in tumour FDG-uptake and volume was found between responding and non-responding patients. No significant difference was found between a visual and semi-quantitative analysis of PET.

CONCLUSION: Response evaluation of SCLC by PET/CT is feasible, but it is uncertain whether it adds further information to evaluation by RECIST, thus further studies and standardization of methods are needed.