The present randomised controlled trial aimed to investigate the effectiveness of a clinical decision support system (CDSS) in assisting clinicians to apply nutritional care to breast cancer (BC) patients during the COVID-19 pandemic in Greece. Adult BC women (stages I-IIIA) who underwent mastectomy followed by hormone therapy were randomly assigned either to the Control group, receiving general nutritional advice, or the Intervention (or CDSS) group, in whom a personalised nutritional programme based on the Mediterranean diet together with physical activity guidelines were provided, all produced by CDSS. Medical and dietary history, anthropometrics, biochemical indices and quality of life characteristics were assessed both at baseline and at the end of the study (3 months).

In this two-armed, single center, randomised controlled 3-month trial, simple randomisation was followed and the randomisation sequence was computer generated by an independent statistician. Blinding of the allocated treatment was maintained to the data analyst and was exposed only after the assessment of outcomes. Adult women (≥ 18 years of age) with histological evidence of primary invasive breast cancer (BC) at stages I-IIIA, who underwent mastectomy followed by antiestrogen therapy, were enrolled in the study. Additional criterion was the ability to ambulate independently, that corresponded to scoring 0 or 1 of the Eastern Cooperative Oncology Performance Status.

At baseline before the start of the trial, each enrolled participant completed a personal interview with the appointed dieticians. In the Intervention group (or CDSS group), patients received a personalised daily dietary plan (specific meals, products, recipes, food portions in grams) based on the Meditteranean diet together with physical activity guidelines, all generated by a newly developed clinical decision support system (CDSS). During the trial, BC women were instructed to record food diaries in the CDSS every week (2 weekdays and 1 weekend day), which were also made available to the dieticians. Visiting the CDSS, patients had the opportunity to track their progress e.g. monitoring goals of body weight, physical activity, consumption of fruits, vegetables, legumes. Regular phone interviews were scheduled on 15-day basis to assist nutritional and lifestyle consultation, while unexpected phone calls were made to receive 24-hour dietary records.

The Control arm received general lifestyle guidelines based on the updated "American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention" via scheduled phone interviews every 15 days. Food diaries of each week (2 weekdays and 1 weekend day) were sent via emails and unexpected phone calls were made to receive 24-hour dietary records as well.

The appointed oncologist recorded medical history, including general information (age, sex, smoking) and disease specific data (i.e. cancer stage, type, age of diagnosis, symptoms and complications, and treatment). All assessments were carried out at the beginning and the end of the study (3 months). Body weight and body fat mass were measured with the method of Air Displacement Plethysmography. Dietary intake was evaluated using a semi-quantitative Food Frequency Questionnaire (FFQ), food diaries and 24h-recall records. The degree of Mediterranean diet adherence was estimated by the MedDiet score. The investigators also assessed performance status and physical activity, as well as quality of life and psychological distress by validated questionnaires. Our hypothesis was that the CDSS could be a useful means to provide nutritional care to BC patients ameliorating adherence to Mediterranean diet and the overall quality of life, during challenging periods like the COVID-19 pandemic.

Inclusion criteria:

• Adult women (≥ 37 years of age);
• histological evidence of primary invasive breast cancer at stages I-IIIA;
• treatment: mastectomy followed by antiestrogen therapy;
• the ability to ambulate independently, that corresponded to scoring 0 or 1 of the Eastern Cooperative Oncology Performance Status

Exclusion criteria:

• Any other malignancy ≤ 5 years;
• co-existing medical conditions (e.g., obstructive ileus) that would interfere with the study protocol;
• malabsorption; serious chronic diseases (e.g. advanced heart, liver or renal failure, congenital metabolic diseases);
• active infection;
• severe psychiatric illness;
• alcoholism or drug use;
• vitamin or inorganic supplement use ≤ 6 months prior to screening;
• vegan or macrobiotic diet ≤ 5 years prior to screening;
• using weight loss medications.