Cardiorespiratory Fitness in Patients With Early-Stage Breast Cancer and Radiation Therapy-Related Fatigue: A Prospective Pilot Study

Abstract

Purpose/ObjectivesFatigue is among the most common but one of the most poorly understood radiotherapy-associated toxicities. This prospective study sought to investigate whether cardiorespiratory fitness, an integrative measure of whole-body cardiopulmonary function, is associated with patient-reported fatigue among women with early-stage breast cancer undergoing radiotherapy. Materials/MethodsPatients with stage Tis-T2N0M0 breast cancer and an ECOG performance status of 0-1 who were undergoing breast radiotherapy performed a symptom-limited cardiopulmonary exercise test (CPET) on a motorized treadmill to assess cardiorespiratory fitness (VO2peak). Fatigue was assessed by the FACIT Fatigue Scale. Both assessments were performed during or immediately after radiotherapy completion. All patients were treated with an opposed tangent technique to a dose of 4240 cGy in 16 fractions with or without a lumpectomy bed boost. Patients receiving cytotoxic chemotherapy were excluded. Pearson's correlation coefficients and univariate linear regression were used to assess associations between VO2peak, fatigue, and patient characteristics. ResultsTwenty-eight patients (median age 52 years, range 31-71) completed both CPET and FACIT assessments. Median VO2peak was 25.1 mL O2.kg−1.min−1 (range 16.7-41.7). The majority of subjects (78.6%) displayed a VO2peak less than their age-predicted VO2peak. Both age and BMI were significantly associated with VO2peak levels. Median fatigue score was 41.5 (range 10-52), with lower values indicating more fatigue. VO2peak was not associated with FACIT score (p=0.20). ConclusionsOverall, VO2peak was not a significant predictor of radiotherapy-related fatigue. Most breast cancer patients had marked impairments in cardiorespiratory fitness as determined by VO2peak. Larger prospective studies are needed to further investigate this novel finding, and to evaluate the effects of interventions aimed at improving cardiorespiratory fitness and their ability to potentially prevent fatigue.