Physical fitness throughout chemotherapy in children with acute lymphoblastic leukaemia and lymphoma

Background and Aims: Due to improving survival rates of patients with childhood acute lymphoblastic leukaemia (ALL), there is an increasing focus on long-term effects of treatment. ALL and its treatment cause a range of physiological changes, interfering with normal physical functioning. So far, it remains unclear how physical fitness (PF) (including muscle strength, functional mobility and endurance) evolves throughout treatment for ALL.

Methods: Sixty-two patients treated for ALL according to the EORTC 58081 protocol underwent physical testing at nine timepoints throughout their 2-year-treatment (last measurement at 6 months post-treatment). Four tests were conducted. Quadriceps and tibialis anterior muscle strength were assessed using a hand-held dynamometer. Standing broad jump test (SBJ) and six-minute walk test (6MWT) were assessed for functional mobility and endurance, respectively. Z-scores were calculated based on gender- and aged-matched test-specific normative values, which were predicted based on time of assessment, ALL risk group and age at diagnosis, using linear mixed models. We added an interaction factor to test whether evolution over time is subject to age.

Results: The strongest decreases in Z-scores are observed after induction therapy in quadriceps strength (Z=-1.36 to Z=-2.62), SBJ (Z=-1.15 to Z=-2.22) and 6MWT scores (Z=-2.20 to Z=-3.57). Age at diagnosis is a significant predictor for tibialis anterior strength (p=0.025), SBJ (p<0.001) and 6MWT (p<0.001) performance. Adolescents (>13 years) tend to have lower results on all performed tests from diagnosis onwards. Muscle strength seems to recover 6 months after treatment (Z=-0.8 for quadriceps strength, Z=0.5 for tibialis anterior strength). However, 6MWT and SBJ scores remained below expected levels, especially for adolescents (Z=-1.63 and Z=-2.58 respectively).

Conclusions: We conclude that future interventions might need to target early decline in PF after induction phase, the low functional mobility and endurance post-treatment, specifically in the adolescent subgroup. These observations can be used to better tailor individualized physiotherapy throughout treatment.