Longitudinal associations of adherence to lifestyle recommendations and health-related quality of life in patients with non-muscle invasive bladder cancer.

Although the role of lifestyle in health-related quality of life (HRQoL) outcomes has been increasingly recognized for various types of cancer, evidence in patients with non-muscle invasive bladder cancer (NMIBC) is very limited. We aimed to evaluate the longitudinal association between adherence to the 2018 World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) lifestyle recommendations and HRQoL in patients with NMIBC. This study included 1,029 patients diagnosed with NMIBC between May 2014-April 2017 from the Dutch multi-centre prospective cohort study UroLife. Lifestyle and HRQoL data were collected at six weeks (baseline), three months, and fifteen months after diagnosis. Information on body mass index (BMI), physical activity, diet, and alcohol was used to compute the standardized WCRF/AICR adherence score (0-7). HRQoL outcomes were evaluated by the EORTC QLQ-C30. Linear mixed models were used to assess longitudinal confounder-adjusted associations between the WCRF/AICR adherence score and HRQoL outcomes. Adherence to each additional WCRF/AICR recommendation was associated with better global quality of life, physical, role, and social functioning, and less fatigue. We found stronger inter-individual than intra-individual associations, suggesting that associations were mainly driven by between-subject differences. Higher adherence to the BMI, physical activity, and dietary recommendations was associated with better scores for most HRQoL outcomes, while adherence to the alcohol recommendation (i.e. non-consumption) was associated with worse HRQoL. Following the WCRF/AICR lifestyle recommendations may improve HRQoL in patients with NMIBC. Intervention studies are needed to establish whether the association between lifestyle and HRQoL is causal.