The aim of our study was to investigate adherence to lifestyle recommendations and lifestyle changes after diagnosis in patients with non-muscle invasive bladder cancer (NMIBC). Second, we aimed to identify distinct trajectories of lifestyle change and their correlates. We analysed data of 935 patients with NMIBC from a prospective cohort study at six weeks (evaluating pre-diagnostic lifestyle), three months, and fifteen months after diagnosis. An overall lifestyle score (range 0–7) was calculated based on the 2018 World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) recommendations focusing on diet, body mass index, and physical activity. Linear mixed models were used to analyse absolute lifestyle changes over time. Distinct trajectories of change were identified with latent class trajectory models. We found an overall lifestyle score of 3.3 which remained constant over time. The largest lifestyle changes were observed for the consumption of red and processed meat (−96 g/week) and fruit and vegetables (−38 g/day). Two to four trajectory groups were identified for each single lifestyle behaviour. Correlates differed per trajectory group. In conclusion, adherence to the WCRF/AICR recommendations was low. Small to moderate changes in and different trajectories of single lifestyle behaviours were observed. Effective strategies for lifestyle improvement are warranted.

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 1029 patients with NMIBC recruited between May 2014 and April 2017 from the Dutch multi‐centre prospective cohort study UroLife. Lifestyle and HRQoL data were collected at 6 weeks (baseline), 3 months and 15 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 (ie, 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.