Pre- and post-diagnosis body weight trajectories in patients with localized renal cell cancer.

Purpose: Obesity in mid-life is a well-established risk factor for developing renal cell carcinoma (RCC); however, patients with RCC who are obese at the time of diagnosis have more favorable survival outcomes. To get better insight into the obesity paradox and determine the extent to which weight around diagnosis is stable, we examined pre- and post-diagnosis weight changes in patients with localized RCC.

Methods: We included 334 patients with localized RCC from the prospective cohort ReLife who self-reported body weight at multiple time points ranging from 2 years before to 2 years after diagnosis. Multivariable linear mixed-effects regression models were used to compare weight at each timepoint to weight at diagnosis for the overall study population, as well as stratified by BMI at diagnosis, tumor stage, and tumor grade.

Results: Most patients were classified as overweight (38.3%) or obese (29.6%) at diagnosis. Overall, patients experienced on average 1.45 kg (95% confidence interval (CI) 0.84, 2.06) weight loss in the 2 years before diagnosis. Pre-diagnosis weight loss was higher in patients who were non-obese at diagnosis, and who presented with higher tumor stage and grade. On average, pre-diagnosis weight loss was at least partially regained within two years after diagnosis.

Conclusion: Patients who were non-obese and patients with higher stage and grade tumors had higher pre-diagnosis weight loss, which was at least partially regained after treatment. These patterns suggest there are subgroups of patients with localized RCC who experience disease-related weight loss, which could contribute to the obesity paradox.