RT Journal Article SR Electronic T1 The Impact That Number of Analyzed Metastatic Breast Cancer Lesions Has on Response Assessment by 18F-FDG PET/CT Using PERCIST JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1102 OP 1104 DO 10.2967/jnumed.115.166629 VO 57 IS 7 A1 Katja Pinker A1 Christopher C. Riedl A1 Leonard Ong A1 Maxine Jochelson A1 Gary A. Ulaner A1 Heather McArthur A1 Maura Dickler A1 Mithad Gönen A1 Wolfgang A. Weber YR 2016 UL http://jnm.snmjournals.org/content/57/7/1102.abstract AB The PET Response Criteria in Solid Tumors (PERCIST) are not specific regarding the number of lesions that should be analyzed per patient. This study evaluated how the number of analyzed lesions affects response assessment in metastatic breast cancer. Methods: In 60 patients, response was assessed by the change in SUVpeak, normalized to lean body mass, of the most 18F-FDG–avid lesion (PERCIST 1) and by the change in the sum of normalized SUVpeak for up to 5 lesions (PERCIST 5). The correlation between response by PERCIST and progression-free and disease-specific survival was evaluated. Results: In responders and nonresponders, the respective progression-free survival at 2 y was 37.26% and 6.43% for PERCIST 1 (P < 0.0001) and 33.65% and 7.14% for PERCIST 5 (P < 0.0001) and the respective disease-specific survival at 4 y was 58.96% and 25.44% for PERCIST 1 (P < 0.012) and 59.12% vs 20.01% for PERCIST 5 (P < 0.002). Conclusion: The number of analyzed lesions does not appear to have a major impact on the prognostic value of response assessment with 18F-FDG PET/CT in metastatic breast cancer.