Abstract RF02-07: Precocious Modulation of Metabolic and Immunological Parameters Predicts Tumor Response to Fasting-Mimicking Diet Plus Chemotherapy in Patients with Early Stage TNBC

Abstract Background: Preclinical studies showed that severely calorie restricted fasting-mimicking diets (FMDs) enhance the antitumor efficacy of chemotherapy (CT) or immunotherapy (IO) in murine triple negative breast cancer (TNBC) models. These effects are mediated by a combination of blood glucose reduction and positive immunomodulatory effects. Moreover, combining fasting and metformin produced synergistic anticancer effects in a broad range of tumor models. The BREAKFAST trial was designed to investigate if FMD, plus/minus metformin, could increase the antitumor activity of neoadjuvant CT in patients with stage I-III TNBC. Methods: BREAKFAST (NCT04248998) is a randomized, non-comparative, phase II, pilot trial that enrolled stage I-III (cT>1 cm) TNBC patients (pts) candidate to receive 4 cycles of neoadjuvant CT with doxorubicin-cyclophosphamide every 3 weeks, followed by 12 cycles of weekly paclitaxel. Pts were randomized 1:1 to receive: CT plus 5-day FMD every 3 weeks, up to 8 cycles (arm A); CT plus FMD plus daily metformin (1700 mg) (arm B). The primary study endpoint was the rate of pCR in either experimental arm. Secondary/exploratory endpoints included safety, compliance, and biomarker analyses based on blood metabolomics and tumor transcriptomics analyses at different timepoints. Results: Between June 2020 and February 2022 we enrolled 30 pts. Then, the study was interrupted after the introduction of chemo-immunotherapy (CT-IO) as a standard neoadjuvant therapy for early stage TNBC pts. Among 30 pts, 13 were treated with CT plus FMD, while 17 pts received CT plus FMD plus metformin. Overall, pCR rate was 56.6%, i.e., significantly higher than pCR rates reported with anthracycline-taxane CT alone in previous phase II/III trials (26-39%), with no significant differences among treatment arms (p=0.49). The FMD acutely reduced blood glucose, insulin and LDH levels, which reflects a reduction in systemic and/or tumor glucose metabolism. Of note, precocious LDH reduction was more pronounced in patients undergoing pCR. RNA-seq analysis of tumor samples revealed a significant downmodulation of glycolysis and TCA cycle pathways after one treatment cycle, paralleled by an increase of intratumor activated T cells, memory T cells and NK cells, as estimated by deconvolution analyses of tumor transcriptomic data. Of note, these changes were observed only in patients achieving pCR. While intratumor metabolic changes were similar in the two treatment arms, the modulation of intratumor immunity was more pronounced in patients not receiving metformin. Conclusion: Preoperative CT plus cyclic FMD (plus/minus metformin) results in excellent pCR rates in localized TNBC patients. Early on-treatment downregulation of systemic and intratumor metabolic parameters related to glucose metabolism predicts pCR, and this is independent of metformin use. Based on results of this study, we recently initiated a large, multicentric trial, namely the BREAKFAST-2 (NCT05763992) study, which will investigate if adding cyclic FMD to neoadjuvant CT-IO increases pCR rates in ~ 145 pts with stage II-III TNBC. Citation Format: Francesca Ligorio, Giovanni Fucà, Andrea Vingiani, Fabio Iannelli, Riccardo Lobefaro, Leonardo Provenzano, Lucrezia Zanenga, Cristina Ferraris, Antonino Belfiore, Silvia Brich, Alessia Bertolotti, Gianfranco Scaperrotta, Catherine Depretto, Antonia Martinetti, Elisa Sottotetti, Paola Antonia Corsetto, Giulia Valeria Bianchi, Giuseppe Capri, Secondo Folli, Saverio Minucci, Marco Foiani, Massimiliano Pagani, Giancarlo Pruneri, Filippo De Braud, Claudio Vernieri. Precocious modulation of metabolic and immunological parameters predicts tumor response to fasting-mimicking diet plus chemotherapy in patients with early stage TNBC [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr RF02-07.