Evaluation of different normalisation procedures for calculation of the standardised uptake value in therapy response monitoring studies Running head: Evaluation of different normalisation procedures

Objectives: The aim of this prospective study was to assess the influence of different normalisation procedures on relative changes in standardised uptake values (SUV) of FDGPET for the assessment of chemotherapy response in patients with colorectal carcinoma (CRC) and non-small cell lung carcinoma (NSCLC). Methods: In 97 patients with CRC 5 (n=48) and NSCLC (n=49) FDG-PET was performed before and during the course of chemotherapy. Relative changes in SUV (ΔSUV) were determined after correction for injected dose and bodyweight, lean body mass, body surface area or a combination of bodyweight and plasma glucose. The predictive value for overall (OS) and progression free survival (PFS) with respect to the different normalised ΔSUVs was assessed. Results: In 10 both CRC and NSCLC no differences were seen in the degree of change between the four SUV-normalisations during chemotherapy. Cox regression analysis for OS showed significant hazard ratios of 1.14-1.16 per ten percent SUV-change in CRC and 1.10-1.13 in NSCLC and for PFS hazard ratios of 1.15 per ten percent ΔSUV-change in CRC and 1.101.12 in NSCLC. Conclusions: Relative change of SUV is a strong predictor for survival in 15 both CRC and NSCLC. None of the four normalisation methods showed statistical advantage over the other. Therefore, simplifying the methods for analysis of FDG-PET data can improve the incorporation of FDG-PET in clinical treatment-response monitoring and may facilitate application in multicentre trials. 20