Purpose The aim of this study was to investigate therelationship between the maximum standardized uptakevalues (SUVmax) of primary renal cancers with and withoutmetastatic lesions, if any. We also studied the relationshipbetween the size of primary renal cancers and their SUVmax,and tried to find a clinical value of 18F-FDG PET-CT for theinitial evaluation of renal cell carcinoma (RCC).
Methods The cases of 23 patients, 16 men and 7 women, whounderwent PET-CT examination before operation wereretrospectively reviewed. We measured the SUVmax of theprimary renal cancers and those of any existing metastaticlesions, and the size of the primary renal cancers. Wecompared the SUVmax of primary RCCs with metastasesand those without metastases, SUVmax of primary RCC andthose of metastases, and studied the correlation between thesize and SUVmax of primary RCCs.
Results The SUVmax of primary RCC of the 16 patientswithout metastasis ranged from 1.1 to 5.6 with a median valueof 2.6. Those of the patients with metastasis ranged from 2.9 to7.6 with a median of 5.0. The size of the all 23 primary renalcancers ranged from 1.7 cm to 13.5 cm, with a median of4.5 cm, and their SUVmax ranged from 1.1 to 7.6, with amedian of 2.9. There was a statistically significant differencebetween the SUVmax of the primary RCC with metastasis (5.3.7) and those without metastasis (2.9.0). There was amoderate positive correlation between the sizes and SUVmaxof all 23 primary RCCs. However, there was no statisticallysignificant correlation between the sizes and SUVmax ofprimary RCCs with metastatic lesions and the same for RCCswithout metastasis. The cutoff value of SUVmax for predictingextra-renal lesion was 4.4 and that for size was 5.8 cmaccording to the receiver operating characteristic curves.
Conclusions Those who have primary RCC with highSUVmax are suggested to have a likelihood of metastasis.
Also, there was a moderate trend of increasing value ofSUVmax of primary RCC as their size increases. Physiciansshould beware of missing extra-renal lesions elsewhere.