Abstract Background: Different types of fasting diet protocols have been associated with a protective effect towards chemotherapy side effects and quality of life. There are not any data of the implementation of a combined protocol including fasting diet against a Mediterranean-type diet in breast cancer patients. Study design: In this randomized clinical trial, 33 newly diagnosed women with early breast cancer were enrolled; Group A (n=16) received a 60 hours fasting diet (36 hours before and 24 hours after chemotherapy) and then guided to follow Mediterranean diet between the chemotherapy cycles, whereas Group B (n=17) received standard of care and no specific diet recommendation. The mean age of Group A and Group B was 45,56±8,23 and 47,35±10,08, respectively. Adherence to Mediterranean diet was assessed by MedDietScore. For each chemotherapy cycle participants were using a self-reported scale to assess adherence to fasting-diet or Mediterranean diet (range 1-10, 1 lower and 10 higher). Results: In total 30.3% (n=10) of the participants received 4 cycles of chemotherapy, 66,67% (n=12) received 6 cycles of chemotherapy and 33.33% (n=11) received 8 cycles of chemotherapy, with no differences between Groups. At baseline, MedDietScore for Group A was 31.47±4.42 and for Group B was 27.93±8.52 (p=0.163). In subgroup analysis for the first four cycles of chemotherapy mean adherence to fasting diet was 8.43/10, whereas adherence to the Mediterranean Diet was 7.79/10. Conclusions: This is the first study reporting data from breast cancer patients following a fasting diet in combination with the Mediterranean Diet. Adherence to both the fasting regimen and the Mediterranean diet was high, indicating that this combined approach is feasible for use in cancer clinical trials. However, its effectiveness in reducing side effects and improving quality of life remains to be established. Citation Format: N. Kontou, D. Tryfonopoulos, A. Apostolou, N. Stavrou, D. Panagiotakos, O. Androutsos. Adherence to Fasting Diet and Mediterranean Diet protocol in women with early stage breast cancer receiving chemotherapy; a randomized clinical trial abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-08-12.
Kontou et al. (Tue,) studied this question.