Tumor burden assessed by maxSUV and metabolic size on FDG-PET predicts prognosis of small cell lung cancer

There are few studies that focused on the prognostic value of FDG-PET on small cell lung cancer (SCLC). Not only FDG uptake (maxSUV), but also metabolic size (greatest dimension of PET positive mass) may determine the prognosis of SCLC. Here, we investigated the prognostic significance of maxSUV, and the metabolic size in SCLC patients. Biopsy-proven SCLC patients (n=21; age, means.d.=67.39y; male: female=19: 3) who had underwent FDG-PET within 4 weeks of chemotherapy initiation were enrolled. There were 7 extensive disease (ED) and 14 limited disease (LD) patients. The maxSUV and the metabolic size were measured, and then, size-incorporated maxSUV (SIMaxSUV = maxSUV x metabolic size) were calculated at individual SCLC masses. SIMaxSUV of main lesion (main-SIMaxSUV), and the summed value of SIMaxSUV of all PET positive masses (summed-SIMaxSUV) were obtained. In addition, age, stage, and %expression of glucose transporter type 1, hexokinase-II, and Ki-67 were evaluated for their association with disease progression. Mean follow up period was 331156 days. Eleven patients experienced disease progression (mean follow up = 23284 days). Univariate analysis revealed that summed-SIMaxSUV and staging were significant predictors of disease progression (p=0.0084 and p=0.0132, respectively). Furthermore, multivariate Cox proportional analysis concluded summed-SIMaxSUV alone was the single independent predictor of disease progression (p=0.0084). Patients with summed-SIMaxSUV=800 (n=6) had lower 1-year progression-free survival rate (0.167) than patients with summed-SIMaxSUV<800 (n=15, 0.457). The degree and the extent of FDG uptake can predict the prognosis of SCLC. The summed value of size-incorporated maxSUV (maxSUV x metabolic size) of all PET positive masses had a greater prognostic significance than stage (ED or LD), which is the established prognostic determinant