Assessment of tumor response to neoadjuvant chemotherapy in patients with breast cancer using MRI and FDG-PET/CT-RECIST 1.1 vs. PERCIST 1.0.

Therapeutic response to neoadjuvant chemotherapy (NAC) for breast cancer based on Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) 1.0 with FDG-PET/CT measurements was evaluated, and the results compared to those obtained with currently widely used Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, based on MRI measurements. MRI and FDG-PET/CT examinations were performed in 32 breast cancer patients before and after the NAC prior to a surgical resection. Chemotherapeutic response of the primary tumor and relapse-free survival (RFS) were investigated using RECIST 1.1 and PERCIST 1.0. Pathological complete response (pCR) was seen in 14 (43.8%) patients, while complete response (CR) was noted in 5, partial response in 25, stable disease in 2, and progressive disease in 0 with RECIST 1.1, and in 28, 2, 1, and 1, respectively, with PERCIST 1.0. For pCR prediction, the sensitivity, specificity, and accuracy with RECIST 1.1 were 28.6% (4/14), 94.4% (17/18), and 65.6% (21/32), and those with PERCIST 1.0 were 100% (14/14), 22.2% (4/18), and 56.3% (18/32). Five patients (15.6%) had recurrent development after a median period of 24 months (range 7.8-66.8 months). Patients who achieved CR shown by RECIST 1.1 showed slightly longer RFS than those who did not (p=0.46), whereas those with complete metabolic response (CMR) based on PERCIST 1.0 showed a relatively longer RFS than non-CMR patients (p=0.087). For prediction of pathological response to NAC in breast cancer, RECIST 1.1 and PERCIST 1.0 have complementary functions, however, FDG-PET as a post-NAC treatment assessment modality remains to be confirmed.