Breast Cancer Blood Flow and Metabolism on Dual-Acquisition 18F-FDG PET: Correlation with Tumor Phenotype and Neoadjuvant Chemotherapy Response

Early changes in tumor glucose metabolism (SUVmax) and in tumor blood flow (BF) have been evaluated separately for monitoring breast cancer response to neoadjuvant chemotherapy (NAC). This study used a single F-18-FDG dual-acquisition PET examination to simultaneously assess these two imaging features and to determine whether they correlate with the same pretherapy tumor phenotypic features and whether they are comparable or complementary in predicting pathologic complete response (pCR). Methods: This prospective study included 150 women with breast cancer and an indication for NAC. A 2-min chest-centered dynamic PET acquisition was performed at the time of F-18-FDG injection, followed by a delayed static PET acquisition 90 min later. Tumor BF was calculated from the dynamic acquisition using a validated first-pass model, and tumor SUVmax was calculated from the delayed acquisition. This dual acquisition was repeated after the first cycle of NAC to measure early changes in tumor BF and SUVmax. Results: A weak correlation was found between SUVmax and BF at baseline (r = 0.22; P = 0.006). A high baseline SUVmax was associated with all biologic markers of tumor aggressiveness, including the triple-negative breast cancer subtype (P < 0.0001). In contrast, a high baseline BF was associated only with obesity (P = 0.002). The change in SUVmax (mean, -44.6% +/- 27.4%) varied depending on the Scarff-Bloom-Richardson grade, overexpression of human epidermal growth factor receptor 2 (HER2-positive), and lack of hormone receptor expression (P = 0.04, P < 0.001, and P = 0.01, respectively). BF (mean change, -26.9% +/- 54.3%) showed a drastic reduction only in HER2-positive subtypes (-58.7% +/- 30.0%), supporting the antiangiogenic effect of trastuzumab. Changes in SUVmax outperformed changes in BF for predicting pCR in all tumor subtypes: the areas under the curve for change in SUVmax were 0.82, 0.65, and 0.90 in the triple-negative, HER2-positive, and luminal subtypes, respectively. Conclusion: Of the two biologic hallmarks of cancer evaluated in this study, a reduction in tumor glucose metabolism was more accurate than a reduction in tumor BF for predicting pCR in the different subtypes of breast cancer.