*2.3. Outcome Analysis*

During the follow-up period, 13/22 patients progressed (according to RECIST). The mean PFS was 12.5 ± 9.2 months. At the end of the study, 12/22 patients had died of thyroid cancer. The mean DSS was 14.2 ± 9.1 months. For detailed PFS and DSS of all patients, see Table S2 in the supplemental information.

PD according to mPERCIST was correlated with worse outcomes and significantly lower PFS and DSS for both time-points. Patients with PD at 3 month follow-up showed a significant lower median PFS (4.0 vs. 24 months, *p* = 0.008) and DSS (20.0 months vs. median not reached for responders, *p* = 0.015) compared to DC (see Figure 3a,c). At the 6 month follow-up, mPERCIST also showed significant differences for both PFS and DSS (PFS 4.0 vs. 15.0 months, *p* = 0.003; DSS 9.0 months vs. the median not reached for responders, *p* = 0.001) between DC and PD (see Figure 3b,d).

**Figure 3.** Kaplan-Meier estimate of PFS (**a**,**b**) and DSS (**c**,**d**) according to mPERCIST criteria for 3 and 6 month follow-up imaging. PFS, progression-free survival; DSS, disease-specific survival; DC, disease control; PD, progressive disease; \* *p*-value < 0.05; \*\* *p*-value < 0.01.

According to the RECIST criteria, PFS did not differ between PD and DC patients at 3 months (15.0 versus 4.0 months, *p* = 0.196) and 6 months (13.0 versus 4.0 months, *p* = 0.114). Patients with PD by RECIST showed a significantly lower median DSS at 3 months (4.0 months versus median not reached, *p* = 0.046) and 6 months (6.5 months versus median not reached, *p* = 0.039; see Table 2).


**Table 2.** Association of PD and DC according to mPERCIST and RECIST to PFS and DSS at the


mPERCIST, modified Positron Emission Tomography Response Criteria In Solid Tumors; RECIST, Response Evaluation Criteria in Solid Tumors; DC, disease control; PD, progressive disease; \* *p*-value < 0.05; \*\* *p*-value < 0.01.

All other PET-parameters showed no significant association to PFS and DSS for both time-points.
