SUVmax by dual time point FDG-PET/CT in recurrent breast cancer: Interobserver, intraobserver and intersoftware variability

Objectives
Calculation of standardized uptake values (SUV) seems to be an important discriminatory factor for accurately diagnosing recurrent breast cancer. We examined the variability in maximum SUV (SUVmax) calculation between observers and types of software at two scan time points.

Methods
18FDG-PET/CT was performed 1 and 3 hours after tracer injection in 25 patients with recurrent breast cancer. At both time points, SUVmax was determined in 79 lesions by two independent observers and twice by observer one (> 2 weeks apart) applying the AW/GEHC workstation software. Observer one repeated the readings using ROVER software without partial volume correction. Pearson correlation analysis and Bland-Altman statistics summarized the data.

Results
The overall mean SUVmax was 8.4 g/mL (SD=3.8) at 1h and 10.9 g/mL (SD=4.7) at 3h. The table displays the Pearson’s r and Bland-Altman statistics. The correlation between the two independent observers at 1h and 3h was relatively modest, with r statistics of 0.88 and 0.89, respectively. The intraobserver and intersoftware analyses showed a high correlation, with r statistics of 0.99 to 1.00.

Conclusions
The interobserver variability was small for both time points, but slightly greater than the intraobserver and intersoftware variability. This could be explained by a difference in observer selection of FDG avid lesions in patients with multiple lesions.


Table
Analysis Pearson’s r (95% CI) Bland-Altman plot
Mean difference (95% CI)
1h Interobserver 0.88 (0.82 – 0.92) -0.35 (-0.78 – 0.07)

3h Interobserver 0.89 (0.83 – 0.93) -0.08 (-0.60 – 0.44)

1h Intraobserver 0.99 (0.99 – 0.99) -0.08 (-0.19 – 0.04)

3h Intraobserver 1.00 (1.00 – 1.00) -0.01 (-0.06 – 0.04)

1h Intersoftware 1.00 (1.00 – 1.00) 0.05 (0.02 – 0.08)

3h Intersoftware 1.00 (0.99 – 1.00) 0.08 (0.00 – 0.17)