Changes in Body Weight Percentile During Primary Anticancer Treatment in Children: A Retrospective Single-Center...

Objective Body weight trajectories may change during anticancer treatment in children. This study aimed to evaluate changes in body weight percentile categories during primary anticancer treatment in pediatric oncology patients and to assess whether the magnitude and direction of these changes were associated with baseline body weight percentile category. Materials and methods This retrospective single-center study included 138 children diagnosed and treated for malignant disease between 2021 and 2025. Body weight was assessed at the initiation and at the completion of primary anticancer treatment using World Health Organization growth standards for children aged 0 to five years and Polish OLAF reference charts for children and adolescents aged six to 17 years. Each measurement was assigned to one of eight predefined centile channels, and continuous analyses were performed on the midpoints of these channels rather than on exact individual percentile values. Body weight percentile categories were analyzed, and changes between baseline and treatment completion were evaluated using the Wilcoxon signed-rank test and the Kruskal-Wallis test. Results Complete paired anthropometric data were available for 138 patients. The mean body weight percentile (channel midpoint) decreased from 56.1 at treatment initiation to 54.65 at treatment completion, while the median remained 62.5 at both assessments. The difference was not statistically significant (p = 0.5254). The proportion of children below the 10th percentile increased from 10.14% to 13.04%, whereas the proportion above the 90th percentile decreased from 22.46% to 16.67%. Most patients remained within the same percentile category or changed by only one category. Baseline body weight percentile category was significantly associated with the distribution of category-change scores (H = 15.25, p = 0.033, η² = 0.06). Children with lower baseline percentiles tended to shift upward, whereas those with higher baseline percentiles tended to shift downward; this pattern should be interpreted with caution, as it may partly reflect regression to the mean and the structurally restricted range of possible change in the extreme categories, in which upward or downward shifts are arithmetically limited. Conclusions Body weight percentiles showed no statistically significant overall change at the population level during primary anticancer treatment; however, individual changes in percentile categories were common. Regular assessment of body weight percentile trajectories may identify changes that are not apparent from group-level measures and may prompt further nutritional assessment. Body weight percentile alone does not provide a comprehensive assessment of nutritional status.