*3.3. Multivariate Analysis*

The two strongest predictive clinical parameters were the number of lesions and the performance status. Adding SUVmax and SUVpeak separately to the multivariate model with these clinical parameters showed that both SUVmax and SUVpeak significantly improved the prediction (*p* = 0.005 and 0.004, respectively), independent of these clinical parameters. HRs were 1.29 per unit increase for SUVmax and 1.36 per unit increase for SUVpeak, independent of the number of lesions and the performance status.

**Table 2.** Clinical variables and PET features in univariate Cox proportional hazard analyses.


**Figure 2.** Examples of lung metastases with different metabolic characteristics. Axial planes of [18F]FDG-PET/CTs of four patients with lung metastases are shown with the corresponding VOIs outlined in orange. (**A**): A metastasis with a SUVmax of 6.1 detected 22 months after resection of an undifferentiated soft tissue sarcoma in the right deltoid muscle. (**B**): A metastasis with a SUVmax of 9.0 detected 34 months after resection of an undifferentiated soft tissue sarcoma in the right gluteus maximus. (**C**): A metastasis with a SUVmax of 5.2 detected synchronous with a myxofibrosarcoma originating from the left thoracic wall. (**D**): A metastasis with a SUVmax of 7.2 detected synchronous with local recurrence of a leiomyosarcoma in the right lower leg.

## *3.4. Survival Estimates*

Median SUVmax and SUVpeak were 5.7 and 4.9 g/mL, respectively. The estimated mean overall survival in patients with SUVmax > 5.7 g/mL was 14 months, and that for patients with SUVmax < 5.7 g/mL was 39 months (*p* < 0.001). For patients with SUVpeak > 4.9 g/mL, the estimated mean overall survival was 18 months, while for those with SUVpeak < 4.9 g/mL, it was 33 months (*p* = 0.04) (Figure 3).

**Figure 3.** Survival curves with the cohort dichotomized at the median SUVmax (**A**) and median SUVpeak (**B**). The grey line represents the survival curve of the entire cohort. The estimated mean overall survival in patients with SUVmax > 5.7 g/mL was 14 months, and that for patients with SUVmax < 5.7 g/mL was 39 months (*p* < 0.001). For patients with SUVpeak > 4.9 g/mL, the estimated mean overall survival was 18 months, while for those with SUVpeak < 4.9 g/mL, it was 33 months (*p* = 0.04).
