140 FDG positron emission tomography maximum standardised uptake value (SUVmax) has prognostic value in non-small cell lung cancer treated with radical radiotherapy

Introduction: FDG-PET (positron emission tomography) scanning gives essential anatomical/staging information for decision making prior to radical treatment in non-small cell lung cancer (NSCLC). The standardised uptake value (SUV) gives physiological data based on glucose uptake/metabolism of tumour which may be of prognostic value in addition to the known anatomical/staging information. Method: Retrospective single centre study of biopsy confirmed NSCLC treated with radical RT (+/ chemotherapy). Survival assessed in two groups: PET SUVmax 4 vs PET SUV max >4. Standard 3D PET scans were obtained either in Cheltenham or Cardiff, SUV max as per radiologist report was used. Relationship between PET SUVmax and stage were also investigated: PET SUVmax vs primary tumour size and by LN status/stage group (I/II/III). Results: 103 patients included (6 had SUV max 4; 97 had SUV max >4). 7 had no value for primary tumour size but did have all other information available. There were significant differences in both progression free and overall survival (p = 0.01 and p = 0.02 respectively) between these two groups, although the very small numbers in the SUVmax 4 mean this result should be interpreted with caution. SUVmax was correlated with primary tumour size (Spearman rank correlation coefficient = 0.41) but was independent of TNM stage group (p = 0.95) and LN involvement (p = 0.59). Conclusions: In this study, biopsy confirmed, very low SUV tumours (PET SUVmax 4) had better survival after radical radiotherapy than those with higher SUVmax, supporting the hypothesis that this is of prognostic significance. A major drawback in this study was the very low number of patients with low SUVmax tumours. Further work is warranted to assess the prognostic value of PET SUVmax and any predictive value of PET SUVmax (eg radiotherapy dose/fractionation and the use of chemotherapy).