Health-Related Quality of Life after Radiotherapy: Epistemological, methodological and clinical issues
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Background: Advances in the diagnosis and treatment of cancer have led to increasing survival rates, and fortunately, more cancer patients are becoming cancer survivors. The other side of the coin is that more people are living with a cancer diagnosis and therefore must live with the potential impact of cancer treatment on health and QoL. Health-related quality of life (HRQoL) covers relevant symptoms, functions, health and QoL, so it is an important patient-reported outcome (PRO) in clinical trials. In addition to objective measures like tumour response and survival, HRQoL may provide valuable information about the total impact of treatment. In reports of side effects after radiotherapy (RT), specifically those addressing late effects, data are mainly from periods with now outdated treatment regimens. In order to develop tailored follow-up regimens, there is a need to evaluate the level and the course of HRQoL after current cancer treatments. Aims: The overall aim of this thesis was to gain insight into epistemological and methodological issues of patient-reported outcomes (PRO), and to employ these methods into exploring HRQoL-domains, with special emphasis on fatigue, after contemporary RT of breast cancer (BC) patients. Methods: The present thesis is based on two separate studies in different populations. Study I validated a diagnosis-specific questionnaire for prostate cancer (PC) patients (Paper I). The epistemological approach of PRO-assessments from Study I conveyed the direction and methods in Study II, where HRQoL-dimensions were assessed longitudinally in 250 BC patients; before RT (baseline), immediately after RT, and at three, six and 12 months after RT. Clinical-, treatment- and sociodemographic data were collected at baseline. Fatigue in BC patients was compared to fatigue of a sample from the Norwegian general population (GenPop), by using data from a previous crosssectional survey (Paper II and Paper III). Results: A positivistic approach constituted the epistemological framework used in this thesis. One consistent sub-domain of symptoms was identified in the PC questionnaire. Breast symptoms and fatigue increased significantly during RT. Among the symptoms, fatigue had the highest mean score immediately after RT, and the increase during RT was, to some extent, explained by the patient’s body-volume receiving high doses (V40). The patients reported stable psychosocial functioning and a slightly better future perspective during RT. Patients treated with chemotherapy (CT) had significantly higher baseline levels of fatigue. However, from end of RT and at all subsequent assessments, similar fatigue levels were evident in patients with and without CT treatment. The extent of RT or hormonal treatment had no influence on the level or the course of fatigue. Patients with comorbidity reported elevated levels of fatigue at all assessments, and so comorbidity was significantly associated with more fatigue, independently of adjuvant treatments. Reassuringly, BC patients were not significantly more fatigued than the GenPop except for immediately after RT. Conclusions: Within a positivistic framework, we conclude that BC patients report few changes in HRQoL domains during current RT. However, fatigue increased significantly during RT, and V40 explained some of this increase. Comorbidity seems to be a more important determinant for fatigue levels than the cancer treatment. Similar fatigue levels in BC patients and the GenPop is promising, but longer follow-up and more extended measures of fatigue are necessary. The results highlight the importance of valid information of comorbid chronic conditions when evaluating fatigue after BC treatment, especially for rehabilitation purposes. Future research should study the course of other HRQoL-domains after treatment with regards to comorbidity. Finally, research within this field needs to be complemented by other scientific approaches to get closer to the “true picture” of HRQoL after current treatment in BC patients.