The effect of f-18 fdg PET-CT to the management of patients with testicular cancer: The evaluation of relation between standart uptake value (SUV) and histopathology, pathologic stage, serum tumor marker levels

Aim: In our study, we evaluated the role of F-18 FDG PET-CT in the management of patients with testicular cancer who underwent F-18 FDG PET-CT examination for post-operative staging, evaluation of treatment response and restaging. Also we investigated the relation between standard uptake value (SUV) calculated from PET images and testicular tumor histological subtypes, stage of the disease and serum tumor marker levels.Methods: 30 patients with testicular cancer who were referred to Dokuz Eylül University School of Medicine Department of Nuclear Medicine for staging, evaluation of treatment response and restaging with F-18 FDG PET-CT between March 2009 and July 2012 were included in our study. SUVmax, SUV mean values of metastatic lesions were calculated from PET images. HUmax, HUmean values and maximum size of lesions with the highest SUVmax value were calculated from CT images. We evaluated the relation between F-18 FDG uptake of residual-metastatic lesions and CT findings of lesions (lesion size, HU values) serum tumor markers, primary tumor histopatology and pathologic stage.Results: There was a significant difference between the SUVmax values of viable tumor positive and viable tumor negative lesions (p=0.01). But there was no significant difference between the SUVmean values of viabl tumor positive and viable tumor negative lesions (p=0.06).There was a correlation of SUVmax with HUmax (r=0.42 p=0.01) and SUV max with HUmean (r=0.36 p=0.03) values of residual lesions.There was no significant difference between the SUVmax values according to the pathologic stage (p=0.3). There was also no significant difference between the SUVmean values according to the pathologic stage (p=0.2).There was significant difference between the SUVmax values of viable tumor positive lesıons according to the serum tumor marker levels (p=0.00). Also we found correlation of SUVmax values and serum tumor marker levels in the viable tumor positive residual lesions (r=0.52 p=0.01).The false negative ratio (%26) of PET imaging in the evaluation of residual lesions was higher than the false positive ratio(%3).In our study, the sensitivity, specificity, PPV, NPV and accuracy of PET in the evaluation of residual lesions were %64, %89, %94, %47 and %71 respectively. We showed that the evaluation of PET and CT images together decreased the false negative ratıo.Conclusion: In our study, the low F-18 FDG uptake of viabl tumor positive residual lesions can be due to low tumor metabolism as described in the literature. But it might also be due to the presense of low density cystic/necrotic heterogeneous residual lesions.We found correlation of F-18 FDG uptake of residual and metastatic lesions with serum tumor marker levels. Statistically there was no significant diffence between F-18 FDG uptake and primary tumor histopathology and pathologic stage.A positive PET result is a strong predictor for the presence of viable tumor. However the high percentage of false negative PET findings limit the prognostic value of PET. Therefore PET negative residual lesions must be evaluated with the other modalities (CT, tumor markers) to make decision for surgery.Key words: F-18 FDG PET-CT, testicular cancer