*3.2. Patient-Based Analysis*

In 67% (47/70), the FDG PET stage was identical to the clinical stage at baseline and in 10% (7/70), FDG PET correctly upstaged patients (Table 2). However, of the remaining 16 patients, 3 were incorrectly downstaged and 13 were incorrectly upstaged. Four patients underwent staging with FDG PET after surgery, as they had stage IIB or III disease postsurgery: one of these patients had an additional suspect breast lesion on FDG PET, and subsequent mastectomy showed multifocal breast cancer.

**Table 2. FDG PET staged 16/70 patients incorrectly compared to final baseline stage.** Patients who received FDG PET imaging prior to surgery or who did not receive surgical treatment are included (*n* = 70). The table indicates the number of patients with their corresponding stage. (A) Staging based on clinical assessment, pathology and conventional imaging performed at baseline. (B) Staging based on FDG PET imaging. (C) Final stage determined after FDG PET imaging, additional imaging and/or biopsy/cytology of new identified suspect lesions.



**Table 2.** *Cont.*

: Correctly identified by FDG PET, : Incorrectly downstaged by FDG PET, : Correctly upstaged by FDG PET, Incorrectly upstaged by FDG PET.

> At the end of follow-up (after 18 months), 81.4% were disease-free (Table S1). Of 67 patients who were diagnosed with locoregional disease at baseline, 3 developed metastases during follow-up. One patient had stage III by FDG PET at baseline; during follow-up, multiple bone metastases were diagnosed after 12 months. The second patient had multiple FDG-avid mediastinal lymph nodes, which were classified as reactive lymph nodes (no biopsy/cytology performed), and 17 months later, she developed pathologically proven liver metastases (without growing mediastinal nodes). The third patient had enhanced uptake in parasternal and paratracheal lymph nodes (no biopsy/cytology performed), which was interpreted at baseline as reactive lymph nodes probably due to esophagitis; 9 months later she presented with mastitis carcinomatosa, growing parasternal lymph nodes and liver metastases.
