Fatigue in cancer: an investigation on fatigue and its origin by aerobic capacity measurement in breast cancer survivors

Exact causes of cancer fatigue is not clear although it may result from combined impacts of many factors including the cancer itself, cancer treatment (chemotherapy, radiation therapy, surgery), associated anemia, pain, sleep disturbance, hormonal changes, poor nutrition and emotions during the process. To date there is no lab tests or any specific test that can reliable and sensitively diagnose or quantify the level of fatigue, yet, there is no conclusive diagnostic tests to differentiate between organic or psychological origin. The aim of this thesis study is to examine whether determination of aerobic capacity will help to differentiate between organic and psychological origin of cancer related fatigue. For this purpose, survived breast cancer patients who were in remission was prospectively enrolled in the study. Fatigue level was assessed by using questionnaires of "Brief Fatigue Inventory" and "Multidimensional Fatigue Inventory", and "Beck Depression Inventory" was used for detecting any depression. Aerobic capacity was determined by the cardiopulmonary exercise test (CPET), using incremental ramp test in which the intensity of was increased gradually until exhaustion. During the test, peak oxygen consumption (VO2 peak), anaerobic threshold, respiratory exchange ratio (RER), heart rate (HR) and respiratory volume and capacities were determined. Subjective data was collected from a total of 35 volunteers and 9 of which was able to perform CPET. Only a small portion reported high level fatique and according to CPET most important deficit was muscle weakness (66% of predicted work-load) followed by moderate aerobic capacity (80.8% of predicted peak VO2). They had significant reserves in terms of heart rate and respiratory capacity. Results of this pioneering work will have importance that could have clinical application because fatigue is a problem in every stages of the cancer process from diagnose through the therapy, but it deserves to be prioritized after the treatment of cancer in cancer survivors. CPET seems to have potential to provide useful information in this respect. Keywords: Aerobic Capacity, Cancer, Cardiopulmonary Exercise Test, Fatigue