Fatigue in childhood cancer is a pervasive and distressing symptom that has a physical component described as a “lack of energy”. Fatigue, physical performance, and a micronutrient, carnitine, all relate to physical energy and may be influenced by chemotherapy. The purpose of this exploratory study was to examine the relationship between the physical performance and carnitine plasma levels and fatigue in child (ages 6 to12) and adolescent (ages 13 to 17) cohorts newly diagnosed with cancer and receiving chemotherapy. Standardized instruments were administered between day 15 and 29 of the 1 st and 3rd cycle of chemotherapy. Instruments included physical performance tests (Timed Up and Down Stairs [TUDS] and 6-Minute Walk test [6MWT]), carnitine plasma levels, and the self-report Childhood Fatigue Scale (CFS) or Fatigue Scale for Adolescents (FS-A).
In the child cohort (n = 16), a Wilcoxon signed rank test showed that the TUDS appeared to improve from cycle 1 to cycle 3 of chemotherapy. The median time in seconds decreased from cycle 1 (Md = 15.88) to cycle 3 (Md = 14.04), z = -1.71, p = .09. Performance on the 6MWT also appeared to improve from cycle 1 to cycle 3. The median distance of meters walked increased from cycle 1 (Md = 359.05) to cycle 3 (Md = 406.40), z = -1.71, p = .09. Levels of free carnitine levels decreased with the median lowering from cycle 1 (Md = 43.0) to cycle 3 (Md = 32.0), z = -2.48, p = .01. Fatigue in children decreased during the first three cycles of chemotherapy. The median on the total score for the CFS decreased from cycle 1 (Md = 18.0) to cycle 3 (Md = 10.5), z = -1.99, p = .05.
In the adolescent cohort (n = 14), the TUDS revealed a slight improvement in physical performance from cycle 1 to cycle 3 of chemotherapy. The median time in seconds decreased from cycle 1 (Md = 10.88) to cycle 3 (Md = 8.30). The distance on the 6MWT evidenced little change from cycle 1 to cycle 3. Free carnitine levels were stable. There was a suggestion that fatigue in the adolescents decreased from cycle 1 to cycle 3 of chemotherapy. The median score on the FS-A decreased from cycle 1 ( Md = 23.5) to cycle 3 (Md = 20.5), z = -1.43, p = .15.
Spearman’s rank-order correlation was used to examine relationships between changes in variables from cycle 1 to 3. In the child cohort, when the TUDS improved, fatigue tended to decrease (rs = .41, p = .11), and when 6MWT improved, fatigue decreased (rs = -.60, p = .01). When free carnitine levels decreased, fatigue decreased (rs = .43, p = .13).
In the adolescent cohort, correlations between changes in the physical performance and fatigue were small. However, when free carnitine decreased, fatigue also decreased (rs = .52, p = .06).
Fatigue may decrease early in treatment as disease symptoms resolve. Fatigue in the child cohort was related to physical performance, which is consistent with previous studies that define fatigue in children as primarily a physical sensation. Adolescent fatigue was not related to physical performance, which supports the concept that, in adolescents, fatigue is more complex and includes mental and emotional components. In both cohorts, a decrease in carnitine levels was not associated with an increase in fatigue.