Acute fatigue in a breast radiotherapy cohort and its relationship to irradiated volumes, body mass index and biological factors

Background Fatigue is the most commonly reported acute effect of breast radiotherapy with approximately 40% of patients experiencing this debilitating symptom. Amelioration of radiation induced fatigue has been hindered by a multifactorial aetiology and an imprecise understanding of the biological pathways whereby a localised treatment causes a systemic effect. Evidence suggests the involvement of an inappropriate neuroimmunological response, mediated via the release of proinflammtory cytokines, like interleukin-6 (1). The agonistic soluble interleukin-6 receptor (sIL6R) is of interest as neural cells only respond to IL-6 in complex with sIL-6R. Therefore, many of the behavioural effects of IL-6 depend on concentrations of sIL-6R. Evidence also identifies Body Mass Index as a risk factor for fatigue, though it is unclear whether this is due to associations between adiposity and, IL-6, increased volumes of radiation or depression and reduced activity. In this study relationships will be sought between both irradiated normal tissue volumes and BMI and inflammatory cytokines at the biochemical level and fatigue at the behavioural level. Methods 100 ‘early’ breast cancer patients receiving no prior systemic therapies and prescribed 45Gy/15#/3 weeks, were consecutively recruited. Fatigue was measured by the Functional Assessment of Cancer Therapy Fatigue Subscale. The volumes of normal tissue within the 10%, 50% and 90% isodose levels were determined via dose-volume histogram analysis. ELISA kits determined circulating levels of sIL-6R. Multiple regression analysis will be utilised. Results The first 50 patients have been recruited and preliminary results will be available by October 2008. References 1. Collado-Hidalgo, A. et al. 2006. Inflammatory biomarkers for persistent fatigue in breast cancer survivors. Clinical Cancer Research 12(9), pp. 2759-2766.