Fatigue is rated as the most distressing side effect of radiotherapy treatment for curable breast cancer. About four-in-ten women treated experience fatigue, which can last for years after treatment. The impact of this debilitating tiredness is loss of independence and impaired physical and mental function. Our study will take a behavioural intervention with demonstrated effect in treating fatigue in a mixed group of chemotherapy patients and adapt it for women undergoing radiotherapy for early breast cancer. The purpose of this trial is to evaluate the feasibility of delivering the intervention in the radiotherapy pathway for patients at a high risk of fatigue and to explore participants’ experiences of the trial and intervention.

A pragmatic single-site non-blinded feasibility trial of a behavioural intervention. Main inclusion criteria are prescription of the UK standard 40Gy in 15 fractions over three weeks radiotherapy (± tumour bed boost) for early (stage 0-IIIa) breast cancer. The total projected sample size after attrition is 70. A previously developed fatigue risk score tool will be used to predict individual’s likelihood of experiencing fatigue. Thirty women predicted to be at a high risk of experiencing significant fatigue will be allocated in the ratio 2:1 to the behavioural intervention or education trial arms, respectively. These feasibility trial participants will be assessed at baseline, after 10 and 15 fractions of radiotherapy, and 10 days, three weeks and six months after radiotherapy. A further 40 women predicted to be at a lower risk of fatigue will join a risk score validation group. Measures to assess feasibility include recruitment, retention and completion rates and variation in implementation of the intervention. Process evaluation with intervention providers and users includes fidelity and adherence checks and qualitative interviews to understand how changes in behaviour are initiated and sustained.

This feasibility study collates data to both inform the progression to and design of a future definitive trial and to refine the intervention. Trial registration: ISRCTN 10303368. Registered August 2017 (retrospectively registered); Health and Care Research Wales Clinical Research Portfolio (CRP) registration 31419.