Predictors of Upper Extremity Function in Breast Cancer Survivors

Deteriorated upper extremity function is a leading cause of potential disability and functional decline in breast cancer survivors (BCS) not only during their active treatment but also in their survivorship continuum. Fatigue and decreased muscle strength are the prominent ones that can account for decreased upper extremity function. Therefore, this study aimed to explore the potential contributors to the upper extremity function of BCS.

A total of 100 BCS were included. Handgrip strength (HGS) was assessed with a dynamometer while fatigue and self-reported upper extremity function were assessed with the Fatigue Severity Scale (FSS), Disabilities of Arm, Shoulder, and Hand Questionnaire (DASH), respectively. To control the potential confounding effect of the handedness, the mean value of HGS was used in the regression model.

HGS was found to be significantly higher on the right side compared to the left side (22.71 ± 3.51 kg vs. 21.45 ± 3.66 kg, t = 5.328, p < 0.001). The mean scores of DASH and FSS were found 21.97 ± 15.62, and 39.62 ± 12.16, respectively. The multivariate linear regression analysis showed that a total of 26.9% of the cumulative variance in DASH is explained by the mean HGS, FSS, and body mass index (BMI) (F (4,95) = 11.793, p < 0.001, R² = 0.269, Cohen's f²:0.54). There were no significant effects and/or interactions of any clinical features of BCS on DASH. FSS and DASH also significantly correlated with each other (r = 0.49, p < 0.001).

This study showed that HGS shows itself as a significant outcome measure to predict upper extremity function in BCS. Because BCS can experience fatigue even years after the completion of primary treatment, it is noteworthy to consider it when evaluating the function of BCS.

ClinicalTrials.gov Identifier: NCT04245657.