Ketogenic diets as an adjuvant therapy for glioblastoma (KEATING): a randomized, mixed methods, feasibility study.

We conducted a feasibility study to investigate the use of ketogenic diets (KDs) as an adjuvant therapy for patients with glioblastoma (GBM), investigating (i) trial feasibility; (ii) potential impacts of the trial on patients' quality of life and health; (iii) patients' perspectives of their decision-making when invited to participate in the trial and (iv) recommending improvements to optimize future phase III trials. A single-center, prospective, randomized, pilot study (KEATING), with an embedded qualitative design. Twelve newly diagnosed patients with GBM were randomized 1:1 to modified ketogenic diet (MKD) or medium chain triglyceride ketogenic diet (MCTKD). Primary outcome was retention at three months. Semi-structured interviews were conducted with a purposive sample of patients and caregivers (n = 15). Descriptive statistics were used for quantitative outcomes and qualitative data were analyzed thematically aided by NVivo. KEATING achieved recruitment targets, but the recruitment rate was low (28.6%). Retention was poor; only four of 12 patients completed the three-month diet (MCTKD n = 3; MKD n = 1). Participants' decisions were intuitive and emotional; caregivers supported diet implementation and influenced the patients' decision to participate. Those who declined made a deliberative and considered decision factoring diet burden and quality of life. A three-month diet was undesirable to patients who declined and withdrew. Recruitment to a KD trial for patients with GBM is possible. A six-week intervention period is proposed for a phase III trial. The role of caregivers should not be underestimated. Future trials should optimize and adequately support the decision-making of patients.