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

Abstract

Fatigue is among the most common but most poorly understood radiation therapy-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 in women with early-stage breast cancer undergoing radiation therapy. Patients with stage Tis-T2N0M0 breast cancer and an Eastern Cooperative Oncology Group performance status of 0 to 1 undergoing breast radiation therapy performed a symptom-limited cardiopulmonary exercise test (CPET) on a motorized treadmill to assess cardiorespiratory fitness as measured by peak oxygen uptake (VO₂peak). Fatigue was assessed using the Functional Assessment of Chronic Illness Therapy (FACIT) Fatigue Scale. Both assessments were performed during or immediately after radiation therapy 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 correlation coefficients and univariate linear regression were used to assess associations amongVO₂peak, fatigue, and patient characteristics. Twenty-eight patients (median age, 52 years; range, 31-71) completed a CPET and FACIT-Fatigue assessment. Median VO₂peak was 25.1 mL O₂^.kg^-1.min^-1 (range, 16.7-41.7). The majority of patients (78.6%) displayed a VO₂peak lower than their age-predicted VO₂peak. Both age and body mass index were significantly associated with VO₂peak levels. The median FACIT-Fatigue score was 41.5 (range, 10-52), with lower values indicating more fatigue. VO₂peak was not significantly associated with FACIT-Fatigue score (P = .20). VO₂peak was not a significant predictor of radiation therapy-related fatigue. Most patients with breast cancer had marked impairments in cardiorespiratory fitness as determined by VO₂peak. Larger prospective studies are needed to further investigate this novel finding and evaluate the effects of interventions aimed at improving cardiorespiratory fitness and their ability to potentially prevent fatigue.