Besides this fundamental primary endpoint, other objectives of the study will be the evaluation of cancer cell proliferation, measured by analyzing Ki67 expression, in patients treated or not with a KD, the evaluation of the activity of the insulin and PI3K pathways, the measurement of changes in weight, body composition, and insulin resistance as well as the occurrence of a ketogenic state when a KD is administered concomitantly to endocrine therapy. Here, PIK3CA is linked to cancer.